The same can be done to test for request header presence/absence or to match based on a specific request header value:

@Controller
@RequestMapping("/owners/{ownerId}")
public class RelativePathUriTemplateController {
@RequestMapping(value = "/pets", method = RequestMethod.GET, headers="myHeader=myValue")
  public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {
    // implementation omitted
          
Although you can match to Content-Type
          and Accept header values using media type wild
          cards (for example "content-type=text/*" will
          match to "text/plain" and
          "text/html"), it is recommended to use the
          consumes and produces
          conditions respectively instead. They are intended specifically for
          that purpose.
      
An @RequestMapping handler method can have
      a very flexible signatures. The supported method arguments and return
      values are described in the following section. Most arguments can be
      used in arbitrary order with the only exception of
      BindingResult arguments. This is described in the
      next section.
      
Note
Spring 3.1 introduced a new set of support classes for
      @RequestMapping methods called
      RequestMappingHandlerMapping and
      RequestMappingHandlerAdapter respectively.
      They are recommended for use and even required to take advantage
      of new features in Spring MVC 3.1 and going forward.
      The new support classes are enabled by default from the MVC namespace and
      with use of the MVC Java config but must be
      configured explicitly if using neither.
      
Supported method argument types
        
The following are the supported method arguments: 

              
Request or response objects (Servlet API). Choose any
              specific request or response type, for example
              ServletRequest or
              HttpServletRequest.
              
Session object (Servlet API): of type
              HttpSession. An argument of this
              type enforces the presence of a corresponding session. As a
              consequence, such an argument is never
              null.
                
Session access may not be thread-safe, in particular in
                a Servlet environment. Consider setting the
                RequestMappingHandlerAdapter's
                "synchronizeOnSession" flag to "true" if multiple requests are
                allowed to access a session concurrently.
              
org.springframework.web.context.request.WebRequest
              org.springframework.web.context.request.NativeWebRequest.
              Allows for generic request parameter access as well as
              request/session attribute access, without ties to the native
              Servlet/Portlet API.
              
java.util.Locale for the current
              request locale, determined by the most specific locale resolver
              available, in effect, the configured
              LocaleResolver in a Servlet
              environment.
              
java.io.InputStream /
              java.io.Reader for access to the
              request's content. This value is the raw InputStream/Reader as
              exposed by the Servlet API.
              
java.io.OutputStream /
              java.io.Writer for generating the
              response's content. This value is the raw OutputStream/Writer as
              exposed by the Servlet API.
              
java.security.Principal
              containing the currently authenticated user.
              
@PathVariable annotated parameters
              for access to URI template variables. See the section called “URI Template Patterns”.
              
@MatrixVariable annotated parameters
              for access to name-value pairs located in URI path segments.
              See the section called “Matrix Variables”.
              
@RequestParam annotated parameters
              for access to specific Servlet request parameters. Parameter
              values are converted to the declared method argument type. See
              the section called “Binding request parameters to method parameters with
        @RequestParam”.
              
@RequestHeader annotated
              parameters for access to specific Servlet request HTTP headers.
              Parameter values are converted to the declared method argument
              type.
              
@RequestBody annotated
              parameters for access to the HTTP request body. Parameter values
              are converted to the declared method argument type using
              HttpMessageConverters. See the section called “Mapping the request body with the @RequestBody
        annotation”.
              
@RequestPart annotated
              parameters for access to the content of a "multipart/form-data"
              request part. See Section 17.10.5, “Handling a file upload request from programmatic clients” and Section 17.10, “Spring's multipart (file upload) support”.
              
HttpEntity<?> parameters for
              access to the Servlet request HTTP headers and contents. The
              request stream will be converted to the entity body using
              HttpMessageConverters. See the section called “Using HttpEntity<?>”.
              
java.util.Map /
              org.springframework.ui.Model /
              org.springframework.ui.ModelMap for
              enriching the implicit model that is exposed to the web
              view.
              
org.springframework.web.servlet.mvc.support.RedirectAttributes
              to specify the exact set of attributes to use in case of a
              redirect and also to add flash attributes (attributes stored
              temporarily on the server-side to make them available to the
              request after the redirect).
              RedirectAttributes is used instead of the
              implicit model if the method returns a "redirect:" prefixed view
              name or RedirectView.
              
Command or form objects to bind request parameters to bean
              properties (via setters) or directly to fields, with
              customizable type conversion, depending on
              @InitBinder methods and/or the
              HandlerAdapter configuration. See the
              webBindingInitializer property on
              RequestMappingHandlerAdapter. Such
              command objects along with their validation results will be
              exposed as model attributes by default, using the command class
              class name - e.g. model attribute "orderAddress" for a command
              object of type "some.package.OrderAddress". The
              ModelAttribute annotation can be used on
              a method argument to customize the model attribute name
              used.
              
org.springframework.validation.Errors
              org.springframework.validation.BindingResult
              validation results for a preceding command or form object (the
              immediately preceding method argument).
              
org.springframework.web.bind.support.SessionStatus
              status handle for marking form processing as complete, which
              triggers the cleanup of session attributes that have been
              indicated by the @SessionAttributes
              annotation at the handler type level.
              
org.springframework.web.util.UriComponentsBuilder
              a builder for preparing a URL relative to the current request's
              host, port, scheme, context path, and the literal part of the
              servlet mapping.
        
The Errors or
        BindingResult parameters have to follow
        the model object that is being bound immediately as the method
        signature might have more that one model object and Spring will create
        a separate BindingResult instance for
        each of them so the following sample won't work:
        
Example 17.1. Invalid ordering of BindingResult and @ModelAttribute

          
@RequestMapping(method = RequestMethod.POST)
public String processSubmit(@ModelAttribute("pet") Pet pet,
    Model model, BindingResult result) { … }
          
Note, that there is a Model
          parameter in between Pet and
          BindingResult. To get this working
          you have to reorder the parameters as follows:
          
@RequestMapping(method = RequestMethod.POST)
public String processSubmit(@ModelAttribute("pet") Pet pet,
    BindingResult result, Model model) { … }
      
Supported method return types
        
The following are the supported return types: 

              
A ModelAndView object, with the
              model implicitly enriched with command objects and the results
              of @ModelAttribute annotated reference data
              accessor methods.
              
A Model object, with the
              view name implicitly determined through a
              RequestToViewNameTranslator and
              the model implicitly enriched with command objects and the
              results of @ModelAttribute annotated
              reference data accessor methods.
              
A Map object for exposing a
              model, with the view name implicitly determined through a
              RequestToViewNameTranslator and
              the model implicitly enriched with command objects and the
              results of @ModelAttribute annotated
              reference data accessor methods.
              
A View object, with the
              model implicitly determined through command objects and
              @ModelAttribute annotated reference data
              accessor methods. The handler method may also programmatically
              enrich the model by declaring a
              Model argument (see above).
              
A String value that is interpreted
              as the logical view name, with the model implicitly determined
              through command objects and @ModelAttribute
              annotated reference data accessor methods. The handler method
              may also programmatically enrich the model by declaring a
              Model argument (see
              above).
              
void if the method handles the response
              itself (by writing the response content directly, declaring an
              argument of type ServletResponse
              / HttpServletResponse for that
              purpose) or if the view name is supposed to be implicitly
              determined through a
              RequestToViewNameTranslator (not
              declaring a response argument in the handler method
              signature).
              
If the method is annotated with
              @ResponseBody, the return type is
              written to the response HTTP body. The return value will be
              converted to the declared method argument type using
              HttpMessageConverters. See the section called “Mapping the response body with the
        @ResponseBody annotation”.
              
A HttpEntity<?> or
              ResponseEntity<?> object to provide
              access to the Servlet response HTTP headers and contents. The
              entity body will be converted to the response stream using
              HttpMessageConverters. See the section called “Using HttpEntity<?>”.
              
A Callable<?> can
              be returned when the application wants to produce the return
              value asynchronously in a thread managed by Spring MVC.
              
A DeferredResult<?> can
              be returned when the application wants to produce the return
              value from a thread of its own choosing.
              
Any other return type is considered to be a single model
              attribute to be exposed to the view, using the attribute name
              specified through @ModelAttribute at the
              method level (or the default attribute name based on the return
              type class name). The model is implicitly enriched with command
              objects and the results of @ModelAttribute
              annotated reference data accessor methods.
      
Binding request parameters to method parameters with
        @RequestParam




    

        
Use the @RequestParam annotation to bind
        request parameters to a method parameter in your controller.
        
The following code snippet shows the usage:
        
@Controller
@RequestMapping("/pets")
@SessionAttributes("pet")
public class EditPetForm {
    // ...
    @RequestMapping(method = RequestMethod.GET)
    public String setupForm(@RequestParam("petId") int petId, ModelMap model) {
        Pet pet = this.clinic.loadPet(petId);
        model.addAttribute("pet", pet);
        return "petForm";
    // ...
        
Parameters using this annotation are required by default, but
        you can specify that a parameter is optional by setting
        @RequestParam's
        required attribute to false
        (e.g., @RequestParam(value="id",
        required=false)).
        
Type conversion is applied automatically if the target method
        parameter type is not String. See the section called “Method Parameters And Type Conversion”.
      
Mapping the request body with the @RequestBody
        annotation
        
The @RequestBody method parameter
        annotation indicates that a method parameter should be bound to the
        value of the HTTP request body. For example:
        
@RequestMapping(value = "/something", method = RequestMethod.PUT)
public void handle(@RequestBody String body, Writer writer) throws IOException {
  writer.write(body);
        
You convert the request body to the method argument by using an
        HttpMessageConverter.
        HttpMessageConverter is responsible for
        converting from the HTTP request message to an object and converting
        from an object to the HTTP response body. The
        RequestMappingHandlerAdapter supports the
        @RequestBody annotation with the following
        default HttpMessageConverters:
            
ByteArrayHttpMessageConverter
            converts byte arrays.
            
StringHttpMessageConverter converts
            strings.
            
FormHttpMessageConverter converts
            form data to/from a MultiValueMap<String, String>.
            
SourceHttpMessageConverter converts
            to/from a javax.xml.transform.Source.
        
For more information on these converters, see Message Converters. Also note
        that if using the MVC namespace or the MVC Java config, a wider
        range of message converters are registered by default.
        See Enabling the MVC Java Config or
        the MVC XML Namespace for more information.
        
If you intend to read and write XML, you will need to configure
        the MarshallingHttpMessageConverter with a
        specific Marshaller and an
        Unmarshaller implementation from the
        org.springframework.oxm package. The example
        below shows how to do that directly in your configuration but if
        your application is configured through the MVC namespace or the
        MVC Java config see Enabling
        the MVC Java Config or the MVC XML Namespace instead.
        
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
    <property name="messageConverters">
      <util:list id="beanList">
        <ref bean="stringHttpMessageConverter"/>
        <ref bean="marshallingHttpMessageConverter"/>
      </util:list>
    </property
</bean>
<bean id="stringHttpMessageConverter"
       class="org.springframework.http.converter.StringHttpMessageConverter"/>
<bean id="marshallingHttpMessageConverter"
      class="org.springframework.http.converter.xml.MarshallingHttpMessageConverter">
  <property name="marshaller" ref="castorMarshaller" />
  <property name="unmarshaller" ref="castorMarshaller" />
</bean>
<bean id="castorMarshaller" class="org.springframework.oxm.castor.CastorMarshaller"/>
        
An @RequestBody method parameter can be
        annotated with @Valid, in which case it will be
        validated using the configured Validator
        instance. When using the MVC namespace or the MVC Java config, a JSR-303 validator
        is configured automatically assuming a JSR-303 implementation is
        available on the classpath.
        
Just like with @ModelAttribute parameters,
        an Errors argument can be used to examine the errors.
        If such an argument is not declared, a
        MethodArgumentNotValidException will be raised.
        The exception is handled in the
        DefaultHandlerExceptionResolver, which sends
        a 400 error back to the client.
          
Also see Enabling the MVC
          Java Config or the MVC XML Namespace for
          information on configuring message converters and a validator
          through the MVC namespace or the MVC Java config.
      
Mapping the response body with the
        @ResponseBody annotation
        
The @ResponseBody annotation is
        similar to @RequestBody. This
        annotation can be put on a method and indicates that the return type
        should be written straight to the HTTP response body (and not placed
        in a Model, or interpreted as a view name). For example:
        
@RequestMapping(value = "/something", method = RequestMethod.PUT)
@ResponseBody
public String helloWorld()  {
  return "Hello World";
        
The above example will result in the text Hello
        World being written to the HTTP response stream.
        
As with @RequestBody, Spring
        converts the returned object to a response body by using an
        HttpMessageConverter. For more
        information on these converters, see the previous section and Message Converters.
      
Using HttpEntity<?>
        
The HttpEntity is similar to
        @RequestBody and
        @ResponseBody. Besides getting access
        to the request and response body, HttpEntity
        (and the response-specific subclass
        ResponseEntity) also allows access to the
        request and response headers, like so:
        
@RequestMapping("/something")
public ResponseEntity<String> handle(HttpEntity<byte[]> requestEntity) throws UnsupportedEncodingException {
  String requestHeader = requestEntity.getHeaders().getFirst("MyRequestHeader"));
  byte[] requestBody = requestEntity.getBody();
  // do something with request header and body
  HttpHeaders responseHeaders = new HttpHeaders();
  responseHeaders.set("MyResponseHeader", "MyValue");
  return new ResponseEntity<String>("Hello World", responseHeaders, HttpStatus.CREATED);
        
The above example gets the value of the
        MyRequestHeader request header, and reads the body
        as a byte array. It adds the MyResponseHeader to
        the response, writes Hello World to the response
        stream, and sets the response status code to 201 (Created).
        
As with @RequestBody and
        @ResponseBody, Spring uses
        HttpMessageConverter to convert from
        and to the request and response streams. For more information on these
        converters, see the previous section and Message Converters.
      
Using @ModelAttribute on a
        method
        
The @ModelAttribute annotation
        can be used on methods or on method arguments. This section explains
        its usage on methods while the next section explains its usage on
        method arguments.
        
An @ModelAttribute on a method
        indicates the purpose of that method is to add one or more model
        attributes. Such methods support the same argument types as
        @RequestMapping methods but cannot be
        mapped directly to requests. Instead
        @ModelAttribute methods in a controller
        are invoked before @RequestMapping
        methods, within the same controller. A couple of examples:
        
// Add one attribute
// The return value of the method is added to the model under the name "account"
// You can customize the name via @ModelAttribute("myAccount")
@ModelAttribute
public Account addAccount(@RequestParam String number) {
    return accountManager.findAccount(number);
// Add multiple attributes
@ModelAttribute
public void populateModel(@RequestParam String number, Model model) {
    model.addAttribute(accountManager.findAccount(number));
    // add more ...
        
@ModelAttribute methods are used
        to populate the model with commonly needed attributes for example to
        fill a drop-down with states or with pet types, or to retrieve a
        command object like Account in order to use it to represent the data
        on an HTML form. The latter case is further discussed in the next
        section.
        
Note the two styles of
        @ModelAttribute methods. In the first,
        the method adds an attribute implicitly by returning it. In the
        second, the method accepts a Model and adds any
        number of model attributes to it. You can choose between the two
        styles depending on your needs.
        
A controller can have any number of
        @ModelAttribute methods. All such
        methods are invoked before
        @RequestMapping methods of the same
        controller.
        
@ModelAttribute methods can also
        be defined in an @ControllerAdvice-annotated
        class and such methods apply to all controllers.
        The @ControllerAdvice annotation is
        a component annotation allowing implementation classes to be autodetected
        through classpath scanning.
          
What happens when a model attribute name is not explicitly
          specified? In such cases a default name is assigned to the model
          attribute based on its type. For example if the method returns an
          object of type Account, the default name used
          is "account". You can change that through the value of the
          @ModelAttribute annotation. If adding
          attributes directly to the Model, use the
          appropriate overloaded addAttribute(..) method -
          i.e., with or without an attribute name.
        
The @ModelAttribute annotation
        can be used on @RequestMapping methods
        as well. In that case the return value of the
        @RequestMapping method is interpreted
        as a model attribute rather than as a view name. The view name is
        derived from view name conventions instead much like for methods
        returning void — see Section 17.12.3, “The View -
      RequestToViewNameTranslator”.
      
Using @ModelAttribute on a
        method argument




    

        
As explained in the previous section
        @ModelAttribute can be used on methods
        or on method arguments. This section explains its usage on method
        arguments.
        
An @ModelAttribute on a method
        argument indicates the argument should be retrieved from the model. If
        not present in the model, the argument should be instantiated first
        and then added to the model. Once present in the model, the argument's
        fields should be populated from all request parameters that have
        matching names. This is known as data binding in Spring MVC, a very
        useful mechanism that saves you from having to parse each form field
        individually.
        
@RequestMapping(value="/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST)
public String processSubmit(@ModelAttribute Pet pet) {
        
Given the above example where can the Pet instance come from?
        There are several options:
            
It may already be in the model due to use of
            @SessionAttributes — see the section called “Using @SessionAttributes to store model
        attributes in the HTTP session between requests”.
            
It may already be in the model due to an
            @ModelAttribute method in the same
            controller — as explained in the previous section.
            
It may be retrieved based on a URI template variable and
            type converter (explained in more detail below).
            
It may be instantiated using its default constructor.
        
An @ModelAttribute method is a
        common way to to retrieve an attribute from the database, which may
        optionally be stored between requests through the use of
        @SessionAttributes. In some cases it
        may be convenient to retrieve the attribute by using an URI template
        variable and a type converter. Here is an example:
        
@RequestMapping(value="/accounts/{account}", method = RequestMethod.PUT)
public String save(@ModelAttribute("account") Account account) {
        
In this example the name of the model attribute (i.e. "account")
        matches the name of a URI template variable. If you register
        Converter<String, Account> that can turn
        the String account value into an
        Account instance, then the above example will
        work without the need for an
        @ModelAttribute method.
        
The next step is data binding. The
        WebDataBinder class matches request parameter
        names — including query string parameters and form fields — to model
        attribute fields by name. Matching fields are populated after type
        conversion (from String to the target field type) has been applied
        where necessary. Data binding and validation are covered in Chapter 7, Validation, Data Binding, and Type Conversion. Customizing the data binding process for a
        controller level is covered in the section called “Customizing WebDataBinder
        initialization”.
        
As a result of data binding there may be errors such as missing
        required fields or type conversion errors. To check for such errors
        add a BindingResult argument immediately
        following the @ModelAttribute
        argument:
        
@RequestMapping(value="/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST)
public String processSubmit(@ModelAttribute("pet") Pet pet, BindingResult result) {
    if (result.hasErrors()) {
        return "petForm";
    // ...
        
With a BindingResult you can check if
        errors were found in which case it's common to render the same form
        where the errors can be shown with the help of Spring's
        <errors> form tag.
        
In addition to data binding you can also invoke validation using
        your own custom validator passing the same
        BindingResult that was used to record data
        binding errors. That allows for data binding and validation errors to
        be accumulated in one place and subsequently reported back to the
        user:
        
@RequestMapping(value="/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST)
public String processSubmit(@ModelAttribute("pet") Pet pet, BindingResult result) {
    new PetValidator().validate(pet, result);
    if (result.hasErrors()) {
        return "petForm";
    // ...
        
Or you can have validation invoked automatically by adding the
        JSR-303 @Valid annotation:
        
@RequestMapping(value="/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST)
public String processSubmit(@Valid @ModelAttribute("pet") Pet pet, BindingResult result) {
    if (result.hasErrors()) {
        return "petForm";
    // ...
        
See Section 7.8, “Spring 3 Validation” and Chapter 7, Validation, Data Binding, and Type Conversion for details on how to configure and use
        validation.
      
Using @SessionAttributes to store model
        attributes in the HTTP session between requests
        
The type-level @SessionAttributes
        annotation declares session attributes used by a specific handler.
        This will typically list the names of model attributes or types of
        model attributes which should be transparently stored in the session
        or some conversational storage, serving as form-backing beans between
        subsequent requests.
        
The following code snippet shows the usage of this annotation,
        specifying the model attribute name:
        
@Controller
@RequestMapping("/editPet.do")
@SessionAttributes("pet")
public class EditPetForm {
    // ...
          
When using controller interfaces (e.g., for AOP proxying),
          make sure to consistently put all your mapping
          annotations - such as @RequestMapping
          and @SessionAttributes - on the
          controller interface rather than on the
          implementation class.
      
Specifying redirect and flash attributes
        
By default all model attributes are considered to be exposed as
        URI template variables in the redirect URL. Of the remaining
        attributes those that are primitive types or collections/arrays of
        primitive types are automatically appended as query parameters.
        
In annotated controllers however the model may contain
        additional attributes originally added for rendering purposes (e.g.
        drop-down field values). To gain precise control over the attributes
        used in a redirect scenario, an
        @RequestMapping method can declare an
        argument of type RedirectAttributes and
        use it to add attributes for use in
        RedirectView. If the controller method does
        redirect, the content of
        RedirectAttributes is used. Otherwise
        the content of the default Model is
        used.
        
The RequestMappingHandlerAdapter provides
        a flag called "ignoreDefaultModelOnRedirect" that
        can be used to indicate the content of the default
        Model should never be used if a
        controller method redirects. Instead the controller method should
        declare an attribute of type
        RedirectAttributes or if it doesn't do
        so no attributes should be passed on to
        RedirectView. Both the MVC namespace and the
        MVC Java config keep this flag set to false in order to maintain
        backwards compatibility. However, for new applications we recommend
        setting it to true
        
The RedirectAttributes interface
        can also be used to add flash attributes. Unlike other redirect
        attributes, which end up in the target redirect URL, flash attributes
        are saved in the HTTP session (and hence do not appear in the URL).
        The model of the controller serving the target redirect URL
        automatically receives these flash attributes after which they are
        removed from the session. See Section 17.6, “Using flash attributes”
        for an overview of the general support for flash attributes in Spring
      
Working with
        "application/x-www-form-urlencoded" data
        
The previous sections covered use of
        @ModelAttribute to support form
        submission requests from browser clients. The same annotation is
        recommended for use with requests from non-browser clients as well.
        However there is one notable difference when it comes to working with
        HTTP PUT requests. Browsers can submit form data via HTTP GET or HTTP
        POST. Non-browser clients can also submit forms via HTTP PUT. This
        presents a challenge because the Servlet specification requires the
        ServletRequest.getParameter*() family of methods to
        support form field access only for HTTP POST, not for HTTP PUT.
        
To support HTTP PUT and PATCH requests, the spring-web
        module provides the filter
        HttpPutFormContentFilter, which can be
        configured in web.xml:
        
<filter>
  <filter-name>httpPutFormFilter</filter-name>
  <filter-class>org.springframework.web.filter.HttpPutFormContentFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>httpPutFormFilter</filter-name>
  <servlet-name>dispatcherServlet</servlet-name>
</filter-mapping>
<servlet>
  <servlet-name>dispatcherServlet</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
</servlet>
        
The above filter intercepts HTTP PUT and PATCH requests with content type
        application/x-www-form-urlencoded, reads the form
        data from the body of the request, and wraps the
        ServletRequest in order to make the form data
        available through the
        ServletRequest.getParameter*() family of
        methods.
          
As HttpPutFormContentFilter consumes the body of the
          request, it should not be configured for PUT or PATCH URLs that rely on other
          converters for application/x-www-form-urlencoded. This includes
          @RequestBody MultiValueMap<String, String> and
          HttpEntity<MultiValueMap<String, String>>.
      
Mapping cookie values with the @CookieValue annotation




    

        
The @CookieValue annotation
        allows a method parameter to be bound to the value of an HTTP
        cookie.
        
Let us consider that the following cookie has been received with
        an http request:
        
JSESSIONID=415A4AC178C59DACE0B2C9CA727CDD84
        
The following code sample demonstrates how to get the value of
        the JSESSIONID cookie:
        
@RequestMapping("/displayHeaderInfo.do")
public void displayHeaderInfo(@CookieValue("JSESSIONID") String cookie)  {
  //...
        
Type conversion is applied automatically if the target method
        parameter type is not String. See the section called “Method Parameters And Type Conversion”.
        
This annotation is supported for annotated handler methods in
        Servlet and Portlet environments.
      
Mapping request header attributes with the @RequestHeader
        annotation
        
The @RequestHeader annotation
        allows a method parameter to be bound to a request header.
        
Here is a sample request header:
Host                    localhost:8080
Accept                  text/html,application/xhtml+xml,application/xml;q=0.9
Accept-Language         fr,en-gb;q=0.7,en;q=0.3
Accept-Encoding         gzip,deflate
Accept-Charset          ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive              300
        
The following code sample demonstrates how to get the value of
        the Accept-Encoding and
        Keep-Alive headers:
        
@RequestMapping("/displayHeaderInfo.do")
public void displayHeaderInfo(@RequestHeader("Accept-Encoding") String encoding,
                              @RequestHeader("Keep-Alive") long keepAlive)  {
  //...
        
Type conversion is applied automatically if the method parameter
        is not String. See the section called “Method Parameters And Type Conversion”.
          
Built-in support is available for converting a comma-separated
          string into an array/collection of strings or other types known to
          the type conversion system. For example a method parameter annotated
          with @RequestHeader("Accept") may be of type
          String but also
          String[] or
          List<String>.
        
This annotation is supported for annotated handler methods in
        Servlet and Portlet environments.
      
Method Parameters And Type Conversion
        
String-based values extracted from the request including request
        parameters, path variables, request headers, and cookie values may
        need to be converted to the target type of the method parameter or
        field (e.g., binding a request parameter to a field in an
        @ModelAttribute parameter) they're
        bound to. If the target type is not String,
        Spring automatically converts to the appropriate type. All simple
        types such as int, long, Date, etc. are supported. You can further
        customize the conversion process through a
        WebDataBinder (see the section called “Customizing WebDataBinder
        initialization”) or by registering
        Formatters with the
        FormattingConversionService (see Section 7.6, “Spring 3 Field Formatting”).
      
Customizing WebDataBinder
        initialization
        
To customize request parameter binding with PropertyEditors
        through Spring's WebDataBinder, you can use
        @InitBinder-annotated methods within
        your controller, @InitBinder methods
        within an @ControllerAdvice class,
        or provide a custom
        WebBindingInitializer.
        
Customizing data binding with
          @InitBinder
          
Annotating controller methods with
          @InitBinder allows you to configure
          web data binding directly within your controller class.
          @InitBinder identifies methods that
          initialize the WebDataBinder that will be
          used to populate command and form object arguments of annotated
          handler methods.
          
Such init-binder methods support all arguments that
          @RequestMapping supports, except for
          command/form objects and corresponding validation result objects.
          Init-binder methods must not have a return value. Thus, they are
          usually declared as void. Typical arguments
          include WebDataBinder in combination with
          WebRequest or
          java.util.Locale, allowing code to register
          context-specific editors.
          
The following example demonstrates the use of
          @InitBinder to configure a
          CustomDateEditor for all
          java.util.Date form properties.
          
@Controller
public class MyFormController {
    @InitBinder
    public void initBinder(WebDataBinder binder) {
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
        dateFormat.setLenient(false);
        binder.registerCustomEditor(Date.class, new CustomDateEditor(dateFormat, false));
    // ...
        
Configuring a custom
          WebBindingInitializer
          
To externalize data binding initialization, you can provide a
          custom implementation of the
          WebBindingInitializer interface,
          which you then enable by supplying a custom bean configuration for
          an AnnotationMethodHandlerAdapter, thus
          overriding the default configuration.
          
The following example from the PetClinic application shows a
          configuration using a custom implementation of the
          WebBindingInitializer interface,
          org.springframework.samples.petclinic.web.ClinicBindingInitializer,
          which configures PropertyEditors required by several of the
          PetClinic controllers.
          
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
    <property name="cacheSeconds" value="0" />
    <property name="webBindingInitializer">
        <bean class="org.springframework.samples.petclinic.web.ClinicBindingInitializer" />
    </property>
</bean>
        
Customizing data binding with externalized
          @InitBinder methods
          
@InitBinder methods can also
          be defined in an @ControllerAdvice-annotated
          class in which case they apply to all controllers. This provides an
          alternative to using a WebBindingInitializer.
          
The @ControllerAdvice annotation is
          a component annotation allowing implementation classes to be autodetected
          through classpath scanning.
        
An @RequestMapping method may
        wish to support 'Last-Modified' HTTP requests, as
        defined in the contract for the Servlet API's
        getLastModified method, to facilitate content
        caching. This involves calculating a lastModified
        long value for a given request, comparing it
        against the 'If-Modified-Since' request header
        value, and potentially returning a response with status code 304 (Not
        Modified). An annotated controller method can achieve that as
        follows:
        
@RequestMapping
public String myHandleMethod(WebRequest webRequest, Model model) {
    long lastModified = // 1. application-specific calculation
    if (request.checkNotModified(lastModified)) {
        // 2. shortcut exit - no further processing necessary
        return null;
    // 3. or otherwise further request processing, actually preparing content
    model.addAttribute(...);
    return "myViewName";
        
There are two key elements to note: calling
        request.checkNotModified(lastModified) and returning
        null. The former sets the response status to 304
        before it returns true. The latter, in combination
        with the former, causes Spring MVC to do no further processing of the
        request.
    
17.3.4 Asynchronous Request Processing
      
Spring MVC 3.2 introduced Servlet 3 based asynchronous request
      processing. Instead of returning a value, as usual, a controller method
      can now return a java.util.concurrent.Callable
      and produce the return value from a separate thread. Meanwhile the main Servlet
      container thread is released and allowed to process other requests.
      Spring MVC invokes the Callable in a
      separate thread with the help of a TaskExecutor
      and when the Callable returns, the
      request is dispatched back to the Servlet container to resume
      processing with the value returned by the
      Callable.
      Here is an example controller method:
      
@RequestMapping(method=RequestMethod.POST)
public Callable<String> processUpload(final MultipartFile file) {
  return new Callable<String>() {
    public Object call() throws Exception {
      // ...
      return "someView";
      
A second option is for the controller to return an instance of
      DeferredResult. In this case the return value
      will also be produced from a separate thread. However, that thread is not
      known to Spring MVC. For example the result may be produced in response
      to some external event such as a JMS message, a scheduled task, etc.
      Here is an example controller method:
      
@RequestMapping("/quotes")
@ResponseBody
public DeferredResult<String> quotes() {
  DeferredResult<String> deferredResult = new DeferredResult<String>();
  // Save the deferredResult in in-memory queue ...
  return deferredResult;
// In some other thread...
deferredResult.setResult(data);
      
This may be difficult to understand without any knowledge of the
      Servlet 3 async processing feature. It would certainly help to read up on it.
      At a very minimum consider the following basic facts:
          
A ServletRequest
          can be put in asynchronous mode by calling
          request.startAsync(). The main effect of doing so is
          that the Servlet, as well as any Filters, can exit but the response
          will remain open allowing some other thread to complete processing.
          
The call to request.startAsync() returns an
          AsyncContext, which can be used for
          further control over async processing. For example it provides
          the method dispatch, which can be called from an
          application thread in order to "dispatch" the request back to
          the Servlet container. An async dispatch is similar to a forward
          except it is made from one (application) thread to another
          (Servlet container) thread whereas a forward occurs synchronously
          in the same (Servlet container) thread.
          
ServletRequest provides access
          to the current DispatcherType, which
          can be used to distinguish if a Servlet or
          a Filter is processing on
          the initial request processing thread and when it is processing in
          an async dispatch.
      
With the above in mind, the following is the sequence
      of events for async request processing with a Callable:
      (1) Controller returns a
      Callable, (2) Spring MVC starts async processing
      and submits the Callable
      to a TaskExecutor
      for processing in a separate thread, (3) the DispatcherServlet
      and all Filter's exit the request processing thread but the response
      remains open, (4) the Callable produces a result
      and Spring MVC dispatches the request back to the Servlet container,
      (5) the DispatcherServlet is invoked again and processing
      resumes with the asynchronously produced result from the
      Callable. The exact sequencing of (2),
      (3), and (4) may vary depending on the speed of execution of the
      concurrent threads.
      
The sequence of events for async request processing with a
      DeferredResult is the same in principal except
      it's up to the application to produce the asynchronous result from some thread:
      (1) Controller returns a DeferredResult and saves it
      in some in-memory queue or list where it can be accessed,
      (2) Spring MVC starts async processing, (3) the DispatcherServlet
      and all configured Filter's exit the request processing thread but the response
      remains open, (4) the application sets the DeferredResult
      from some thread and Spring MVC dispatches the request back to the Servlet container,
      (5) the DispatcherServlet is invoked again and processing
      resumes with the asynchronously produced result.
      
Explaining the motivation for async request processing and when or why to use it
      are beyond the scope of this document. For further information you may wish to read
      this blog post series.
      
Exception Handling for Async Requests




    

        
What happens if a Callable returned
        from a controller method raises an Exception while being executed?
        The effect is similar to what happens when any controller method raises
        an exception. It is handled by a matching
        @ExceptionHandler method in the same
        controller or by one of the configured
        HandlerExceptionResolver instances.
          
Under the covers, when a Callable
          raises an Exception, Spring MVC still dispatches to the Servlet
          container to resume processing. The only difference is that the
          result of executing the Callable
          is an Exception that must be processed
          with the configured
          HandlerExceptionResolver instances.
        
When using a DeferredResult, you have
        a choice of calling its setErrorResult(Object) method
        and provide an Exception or any other Object
        you'd like to use as the result. If the result is an
        Exception, it will be processed with a
        matching @ExceptionHandler method in the
        same controller or with any configured
        HandlerExceptionResolver instance.
      
Intercepting Async Requests
        
An existing HandlerInterceptor can
        implement AsyncHandlerInterceptor, which
        provides one additional method afterConcurrentHandlingStarted.
        It is invoked after async processing starts and when the initial
        request processing thread is being exited. See the Javadoc of
        AsyncHandlerInterceptor for more details
        on that.
        
Further options for async request lifecycle callbacks are
        provided directly on DeferredResult,
        which has the methods onTimeout(Runnable) and
        onCompletion(Runnable). Those are called when the
        async request is about to time out or has completed respectively.
        The timeout event can be handled by setting the
        DeferredResult to some value.
        The completion callback however is final and the result can no
        longer be set.
        
Similar callbacks are also available with a
        Callable. However, you will need to wrap
        the Callable in an instance of
        WebAsyncTask and then use that to register
        the timeout and completion callbacks. Just like with
        DeferredResult, the timeout event can be
        handled and a value can be returned while the completion event is final.
        
You can also register a
        CallableProcessingInterceptor or a
        DeferredResultProcessingInterceptor
        globally through the MVC Java config or the MVC namespace.
        Those interceptors provide a full set of callbacks and apply every
        time a Callable or a
        DeferredResult is used.
      
Configuration for Async Request Processing
        
Servlet 3 Async Config
          
To use Servlet 3 async request processing, you need to update
          web.xml to version 3.0:
          
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">
  </web-app>
          
The DispatcherServlet and any
          Filter configuration need to have
          the <async-supported>true</async-supported> sub-element.
          Additionally, any Filter that also needs
          to get involved in async dispatches should also be configured
          to support the ASYNC dispatcher type. Note that it is safe
          to enable the ASYNC dispatcher type for all filters provided with
          the Spring Framework since they will not get involved in async
          dispatches unless needed.
          
If using Servlet 3, Java based configuration, e.g. via
          WebApplicationInitializer, you'll
          also need to set the "asyncSupported" flag as well as the
          ASYNC dispatcher type just like with web.xml.
          To simplify all this configuration, consider
          extending AbstractDispatcherServletInitializer
          or AbstractAnnotationConfigDispatcherServletInitializer,
          which automatically set those options and make it very easy to register
          Filter instances.
        
Spring MVC Async Config
          
The MVC Java config and the MVC namespace both provide options for
          configuring async request processing.
          WebMvcConfigurer has the method
          configureAsyncSupport while <mvc:annotation-driven>
          has an <async-support> sub-element.
          
Those allow you to configure the default timeout value to use for
          async requests, which if not set depends on the underlying Servlet
          container (e.g. 10 seconds on Tomcat). You can also configure an
          AsyncTaskExecutor to use for executing
          Callable instances returned from
          controller methods. It is highly recommended to configure this property
          since by default Spring MVC uses
          SimpleAsyncTaskExecutor. The MVC Java config
          and the MVC namespace also allow you to register
          CallableProcessingInterceptor and
          DeferredResultProcessingInterceptor
          instances.
          
If you need to override the default timeout value for a
          specific DeferredResult, you can do so by using
          the appropriate class constructor. Similarly, for a
          Callable, you can wrap it in a
          WebAsyncTask and use the appropriate class
          constructor to customize the timeout value. The class constructor of
          WebAsyncTask also allows providing
          an AsyncTaskExecutor.
    
In previous versions of Spring, users were required to define one or
    more HandlerMapping beans in the web
    application context to map incoming web requests to appropriate handlers.
    With the introduction of annotated controllers, you generally don't need
    to do that because the RequestMappingHandlerMapping
    automatically looks for @RequestMapping
    annotations on all @Controller beans.
    However, do keep in mind that all HandlerMapping
    classes extending from AbstractHandlerMapping have
    the following properties that you can use to customize their
    behavior:
    
interceptors

          
List of interceptors to use.
          HandlerInterceptors are discussed in
          Section 17.4.1, “Intercepting requests with a
      HandlerInterceptor”.
        
defaultHandler

          
Default handler to use, when this handler mapping does not
          result in a matching handler.
        
order

          
Based on the value of the order property (see the
          org.springframework.core.Ordered interface),
          Spring sorts all handler mappings available in the context and
          applies the first matching handler.
        
alwaysUseFullPath

          
If true , Spring uses the full path within
          the current Servlet context to find an appropriate handler. If
          false (the default), the path within the current
          Servlet mapping is used. For example, if a Servlet is mapped using
          /testing/* and the
          alwaysUseFullPath property is set to true,
          /testing/viewPage.html is used, whereas if the
          property is set to false, /viewPage.html is
          used.
        
urlDecode

          
Defaults to true, as of Spring 2.5. If you
          prefer to compare encoded paths, set this flag to
          false. However, the
          HttpServletRequest always exposes the
          Servlet path in decoded form. Be aware that the Servlet path will
          not match when compared with encoded paths.
    
The following example shows how to configure an interceptor:
    
<beans>
  <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping">
    <property name="interceptors">
      <bean class="example.MyInterceptor"/>
    </property>
  </bean>
<beans>
    
17.4.1 Intercepting requests with a
      HandlerInterceptor




    

      
Spring's handler mapping mechanism includes handler interceptors,
      which are useful when you want to apply specific functionality to
      certain requests, for example, checking for a principal.
      
Interceptors located in the handler mapping must implement
      HandlerInterceptor from the
      org.springframework.web.servlet package. This
      interface defines three methods: preHandle(..) is
      called before the actual handler is executed;
      postHandle(..) is called after
      the handler is executed; and afterCompletion(..) is
      called after the complete request has finished.
      These three methods should provide enough flexibility to do all kinds of
      preprocessing and postprocessing.
      
The preHandle(..) method returns a boolean
      value. You can use this method to break or continue the processing of
      the execution chain. When this method returns true,
      the handler execution chain will continue; when it returns false, the
      DispatcherServlet assumes the interceptor itself
      has taken care of requests (and, for example, rendered an appropriate
      view) and does not continue executing the other interceptors and the
      actual handler in the execution chain.
      
Interceptors can be configured using the
      interceptors property, which is present on all
      HandlerMapping classes extending from
      AbstractHandlerMapping. This is shown in the
      example below:
      
<beans>
    <bean id="handlerMapping"
          class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping">
        <property name="interceptors">
                <ref bean="officeHoursInterceptor"/>
            </list>
        </property>
    </bean>
    <bean id="officeHoursInterceptor"
          class="samples.TimeBasedAccessInterceptor">
        <property name="openingTime" value="9"/>
        <property name="closingTime" value="18"/>
    </bean>
<beans>
      
package samples;
public class TimeBasedAccessInterceptor extends HandlerInterceptorAdapter {
    private int openingTime;
    private int closingTime;
    public void setOpeningTime(int openingTime) {
        this.openingTime = openingTime;
    public void setClosingTime(int closingTime) {
        this.closingTime = closingTime;
    public boolean preHandle(
            HttpServletRequest request,
            HttpServletResponse response,
            Object handler) throws Exception {
        Calendar cal = Calendar.getInstance();
        int hour = cal.get(HOUR_OF_DAY);
        if (openingTime <= hour && hour < closingTime) {
            return true;
        } else {
            response.sendRedirect("http://host.com/outsideOfficeHours.html");
            return false;
      
Any request handled by this mapping is intercepted by the
      TimeBasedAccessInterceptor. If the current time
      is outside office hours, the user is redirected to a static HTML file
      that says, for example, you can only access the website during office
      hours.
        
When using the
        RequestMappingHandlerMapping the actual handler
        is an instance of HandlerMethod which
        identifies the specific controller method that will be invoked.
      
As you can see, the Spring adapter class
      HandlerInterceptorAdapter makes it easier to
      extend the HandlerInterceptor
      interface.
        
In the example above, the configured interceptor will apply to
        all requests handled with annotated controller methods. If you want to
        narrow down the URL paths to which an interceptor applies, you can use
        the MVC namespace or the MVC Java config, or declare bean instances
        of type MappedInterceptor to do that. See Enabling the MVC Java Config or the MVC
        XML Namespace.
    
All MVC frameworks for web applications provide a way to address
    views. Spring provides view resolvers, which enable you to render models
    in a browser without tying you to a specific view technology. Out of the
    box, Spring enables you to use JSPs, Velocity templates and XSLT views,
    for example. See Chapter 18, View technologies for a discussion of how to
    integrate and use a number of disparate view technologies.
    
The two interfaces that are important to the way Spring handles
    views are ViewResolver and
    View. The
    ViewResolver provides a mapping between
    view names and actual views. The View
    interface addresses the preparation of the request and hands the request
    over to one of the view technologies.
    
17.5.1 Resolving views with the
      ViewResolver interface
      
As discussed in Section 17.3, “Implementing Controllers”, all handler
      methods in the Spring Web MVC controllers must resolve to a logical view
      name, either explicitly (e.g., by returning a String,
      View, or ModelAndView) or
      implicitly (i.e., based on conventions). Views in Spring are addressed
      by a logical view name and are resolved by a view resolver. Spring comes
      with quite a few view resolvers. This table lists most of them; a couple
      of examples follow.
      
Table 17.3. View resolvers

        
ViewResolver
Description
AbstractCachingViewResolver
Abstract view resolver that caches views. Often views
              need preparation before they can be used; extending this view
              resolver provides caching.
XmlViewResolver
Implementation of
              ViewResolver that accepts a
              configuration file written in XML with the same DTD as Spring's
              XML bean factories. The default configuration file is
              /WEB-INF/views.xml.
ResourceBundleViewResolver
Implementation of
              ViewResolver that uses bean
              definitions in a ResourceBundle,
              specified by the bundle base name. Typically you define the
              bundle in a properties file, located in the classpath. The
              default file name is
              views.properties.
UrlBasedViewResolver
Simple implementation of the
              ViewResolver interface that
              effects the direct resolution of logical view names to URLs,
              without an explicit mapping definition. This is appropriate if
              your logical names match the names of your view resources in a
              straightforward manner, without the need for arbitrary
              mappings.
InternalResourceViewResolver
Convenient subclass of
              UrlBasedViewResolver that supports
              InternalResourceView (in effect, Servlets
              and JSPs) and subclasses such as JstlView
              and TilesView. You can specify the view
              class for all views generated by this resolver by using
              setViewClass(..). See the Javadocs for the
              UrlBasedViewResolver class for
              details.
VelocityViewResolver /
              FreeMarkerViewResolver
Convenient subclass of
              UrlBasedViewResolver that supports
              VelocityView (in effect, Velocity
              templates) or FreeMarkerView
              ,respectively, and custom subclasses of them.
ContentNegotiatingViewResolver
Implementation of the
              ViewResolver interface that
              resolves a view based on the request file name or
              Accept header. See Section 17.5.4, “ContentNegotiatingViewResolver”.
      
As an example, with JSP as a view technology, you can use the
      UrlBasedViewResolver. This view resolver
      translates a view name to a URL and hands the request over to the
      RequestDispatcher to render the view.
      
<bean id="viewResolver"
      class="org.springframework.web.servlet.view.UrlBasedViewResolver">
    <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
    <property name="prefix" value="/WEB-INF/jsp/"/>
    <property name="suffix" value=".jsp"/>
</bean>
      
When returning test as a logical view name,
      this view resolver forwards the request to the
      RequestDispatcher that will send the request to
      /WEB-INF/jsp/test.jsp.
      
When you combine different view technologies in a web application,
      you can use the
      ResourceBundleViewResolver:
      
<bean id="viewResolver"
      class="org.springframework.web.servlet.view.ResourceBundleViewResolver">
    <property name="basename" value="views"/>
    <property name="defaultParentView" value="parentView"/>
</bean>
      
The ResourceBundleViewResolver inspects the
      ResourceBundle identified by the basename, and
      for each view it is supposed to resolve, it uses the value of the
      property [viewname].(class) as the view class and the
      value of the property [viewname].url as the view url.
      Examples can be found in the next chapter which covers view
      technologies. As you can see, you can identify a parent view, from which
      all views in the properties file “extend”. This way you can
      specify a default view class, for example.
        
Subclasses of AbstractCachingViewResolver
        cache view instances that they resolve. Caching improves performance
        of certain view technologies. It's possible to turn off the cache by
        setting the cache property to
        false. Furthermore, if you must refresh a certain
        view at runtime (for example when a Velocity template is modified),
        you can use the removeFromCache(String viewName, Locale
        loc) method.
    
17.5.2 Chaining ViewResolvers




    

      
Spring supports multiple view resolvers. Thus you can chain
      resolvers and, for example, override specific views in certain
      circumstances. You chain view resolvers by adding more than one resolver
      to your application context and, if necessary, by setting the
      order property to specify ordering. Remember, the
      higher the order property, the later the view resolver is positioned in
      the chain.
      
In the following example, the chain of view resolvers consists of
      two resolvers, an InternalResourceViewResolver,
      which is always automatically positioned as the last resolver in the
      chain, and an XmlViewResolver for specifying
      Excel views. Excel views are not supported by the
      InternalResourceViewResolver.
      
<bean id="jspViewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
  <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>
  <property name="prefix" value="/WEB-INF/jsp/"/>
  <property name="suffix" value=".jsp"/>
</bean>
<bean id="excelViewResolver" class="org.springframework.web.servlet.view.XmlViewResolver">
  <property name="order" value="1"/>
  <property name="location" value="/WEB-INF/views.xml"/>
</bean>
<!-- in views.xml -->
<beans>
  <bean name="report" class="org.springframework.example.ReportExcelView"/>
</beans>
      
If a specific view resolver does not result in a view, Spring
      examines the context for other view resolvers. If additional view
      resolvers exist, Spring continues to inspect them until a view is
      resolved. If no view resolver returns a view, Spring throws a
      ServletException.
      
The contract of a view resolver specifies that a view resolver
      can return null to indicate the view could not be
      found. Not all view resolvers do this, however, because in some cases,
      the resolver simply cannot detect whether or not the view exists. For
      example, the InternalResourceViewResolver uses
      the RequestDispatcher internally, and dispatching
      is the only way to figure out if a JSP exists, but this action can only
      execute once. The same holds for the
      VelocityViewResolver and some others. Check the
      Javadoc for the view resolver to see whether it reports non-existing
      views. Thus, putting an
      InternalResourceViewResolver in the chain in a
      place other than the last, results in the chain not being fully
      inspected, because the
      InternalResourceViewResolver will
      always return a view!
    
17.5.3 Redirecting to views
      
As mentioned previously, a controller typically returns a logical
      view name, which a view resolver resolves to a particular view
      technology. For view technologies such as JSPs that are processed
      through the Servlet or JSP engine, this resolution is usually handled
      through the combination of
      InternalResourceViewResolver and
      InternalResourceView, which issues an internal
      forward or include via the Servlet API's
      RequestDispatcher.forward(..) method or
      RequestDispatcher.include() method. For other view
      technologies, such as Velocity, XSLT, and so on, the view itself writes
      the content directly to the response stream.
      
It is sometimes desirable to issue an HTTP redirect back to the
      client, before the view is rendered. This is desirable, for example,
      when one controller has been called with POSTed data,
      and the response is actually a delegation to another controller (for
      example on a successful form submission). In this case, a normal
      internal forward will mean that the other controller will also see the
      same POST data, which is potentially problematic if
      it can confuse it with other expected data. Another reason to perform a
      redirect before displaying the result is to eliminate the possibility of
      the user submitting the form data multiple times. In this scenario, the
      browser will first send an initial POST; it will then
      receive a response to redirect to a different URL; and finally the
      browser will perform a subsequent GET for the URL
      named in the redirect response. Thus, from the perspective of the
      browser, the current page does not reflect the result of a
      POST but rather of a GET. The end
      effect is that there is no way the user can accidentally
      re-POST the same data by performing a refresh. The
      refresh forces a GET of the result page, not a resend
      of the initial POST data.
      
RedirectView
        
One way to force a redirect as the result of a controller
        response is for the controller to create and return an instance of
        Spring's RedirectView. In this case,
        DispatcherServlet does not use the normal view
        resolution mechanism. Rather because it has been given the (redirect)
        view already, the DispatcherServlet simply
        instructs the view to do its work.
        
The RedirectView issues an
        HttpServletResponse.sendRedirect() call that
        returns to the client browser as an HTTP redirect. By default all
        model attributes are considered to be exposed as URI template
        variables in the redirect URL. Of the remaining attributes those that
        are primitive types or collections/arrays of primitive types are
        automatically appended as query parameters.
        
Appending primitive type attributes as query parameters may be
        the desired result if a model instance was prepared specifically for
        the redirect. However, in annotated controllers the model may contain
        additional attributes added for rendering purposes (e.g. drop-down
        field values). To avoid the possibility of having such attributes
        appear in the URL an annotated controller can declare an argument of
        type RedirectAttributes and use it to
        specify the exact attributes to make available to
        RedirectView. If the controller method decides
        to redirect, the content of
        RedirectAttributes is used. Otherwise
        the content of the model is used.
        
Note that URI template variables from the present request are
        automatically made available when expanding a redirect URL and do not
        need to be added explicitly neither through
        Model nor
        RedirectAttributes. For example:
        
@RequestMapping(value = "/files/{path}", method = RequestMethod.POST)
public String upload(...) {
    // ...
    return "redirect:files/{path}";
        
If you use RedirectView and the view is
        created by the controller itself, it is recommended that you configure
        the redirect URL to be injected into the controller so that it is not
        baked into the controller but configured in the context along with the
        view names. The next section discusses this process.
      
The redirect: prefix
        
While the use of RedirectView works fine,
        if the controller itself creates the
        RedirectView, there is no avoiding the fact
        that the controller is aware that a redirection is happening. This is
        really suboptimal and couples things too tightly. The controller
        should not really care about how the response gets handled. In general
        it should operate only in terms of view names that have been injected
        into it.
        
The special redirect: prefix allows you to
        accomplish this. If a view name is returned that has the prefix
        redirect:, the
        UrlBasedViewResolver (and all subclasses) will
        recognize this as a special indication that a redirect is needed. The
        rest of the view name will be treated as the redirect URL.
        
The net effect is the same as if the controller had returned a
        RedirectView, but now the controller itself can
        simply operate in terms of logical view names. A logical view name
        such as redirect:/myapp/some/resource will redirect
        relative to the current Servlet context, while a name such as
        redirect:http://myhost.com/some/arbitrary/path will
        redirect to an absolute URL.
      
The forward: prefix
        
It is also possible to use a special forward:
        prefix for view names that are ultimately resolved by
        UrlBasedViewResolver and subclasses. This
        creates an InternalResourceView (which
        ultimately does a RequestDispatcher.forward())
        around the rest of the view name, which is considered a URL.
        Therefore, this prefix is not useful with
        InternalResourceViewResolver and
        InternalResourceView (for JSPs for example).
        But the prefix can be helpful when you are primarily using another
        view technology, but still want to force a forward of a resource to be
        handled by the Servlet/JSP engine. (Note that you may also chain
        multiple view resolvers, instead.)
        
As with the redirect: prefix, if the view
        name with the forward: prefix is injected into the
        controller, the controller does not detect that anything special is
        happening in terms of handling the response.
    
17.5.4 ContentNegotiatingViewResolver
      
The ContentNegotiatingViewResolver does not
      resolve views itself but rather delegates to other view resolvers,
      selecting the view that resembles the representation requested by the
      client. Two strategies exist for a client to request a representation
      from the server:
          
Use a distinct URI for each resource, typically by using a
          different file extension in the URI. For example, the URI
          http://www.example.com/users/fred.pdf requests a PDF
          representation of the user fred, and
          http://www.example.com/users/fred.xml requests an
          XML representation.
          
Use the same URI for the client to locate the resource, but
          set the Accept HTTP request header to list the
          media
          types that it understands. For example, an HTTP request for
          http://www.example.com/users/fred with an
          Accept header set to application/pdf
          requests a PDF representation of the user fred, while
          http://www.example.com/users/fred with an
          Accept header set to text/xml
          requests an XML representation. This strategy is known as content
          negotiation.
        
One issue with the Accept header is that it
        is impossible to set it in a web browser within HTML. For example, in
        Firefox, it is fixed to:
        
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
        
For this reason it is common to see the use of a distinct URI
        for each representation when developing browser based web
        applications.
      
To support multiple representations of a resource, Spring provides
      the ContentNegotiatingViewResolver to resolve a
      view based on the file extension or Accept header of
      the HTTP request. ContentNegotiatingViewResolver
      does not perform the view resolution itself but instead delegates to a
      list of view resolvers that you specify through the bean property
      ViewResolvers.
      
The ContentNegotiatingViewResolver selects
      an appropriate View to handle the request by
      comparing the request media type(s) with the media type (also known as
      Content-Type) supported by the
      View associated with each of its
      ViewResolvers. The first
      View in the list that has a compatible
      Content-Type returns the representation to the
      client. If a compatible view cannot be supplied by the
      ViewResolver chain, then the list of views
      specified through the DefaultViews property will be
      consulted. This latter option is appropriate for singleton
      Views that can render an appropriate
      representation of the current resource regardless of the logical view
      name. The Accept header may include wild cards, for
      example text/*, in which case a
      View whose Content-Type was
      text/xml is a compatible match.
      
To support the resolution of a view based on a file extension, use
      the ContentNegotiatingViewResolver bean property
      mediaTypes to specify a mapping of file extensions to
      media types. For more information on the algorithm used to determine the
      request media type, refer to the API documentation for
      ContentNegotiatingViewResolver.
      
Here is an example configuration of a
      ContentNegotiatingViewResolver:
      
<bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
  <property name="mediaTypes">
      <entry key="atom" value="application/atom+xml"/>
      <entry key="html" value="text/html"/>
      <entry key="json" value="application/json"/>
  </property>
  <property name="viewResolvers">
      <bean class="org.springframework.web.servlet.view.BeanNameViewResolver"/>
      <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
      </bean>
    </list>
  </property>
  <property name="defaultViews">
      <bean class="org.springframework.web.servlet.view.json.MappingJackson2JsonView" />
    </list>
  </property>
</bean>
<bean id="content" class="com.springsource.samples.rest.SampleContentAtomView"/>
      
The InternalResourceViewResolver handles
      the translation of view names and JSP pages, while the
      BeanNameViewResolver returns a view based on the
      name of a bean. (See "Resolving views with the
      ViewResolver interface" for more details on how Spring looks up
      and instantiates a view.) In this example, the
      content bean is a class that inherits from
      AbstractAtomFeedView, which returns an Atom RSS
      feed. For more information on creating an Atom Feed representation, see
      the section Atom Views.
      
In the above configuration, if a request is made with an
      .html extension, the view resolver looks for a view
      that matches the text/html media type. The
      InternalResourceViewResolver provides the
      matching view for text/html. If the request is made
      with the file extension .atom, the view resolver
      looks for a view that matches the
      application/atom+xml media type. This view is
      provided by the BeanNameViewResolver that maps to
      the SampleContentAtomView if the view name
      returned is content. If the request is made with
      the file extension .json, the
      MappingJackson2JsonViewinstance from the
      DefaultViews list will be selected regardless of the
      view name. Alternatively, client requests can be made without a file
      extension but with the Accept header set to the
      preferred media-type, and the same resolution of request to views would
      occur.
        
If ContentNegotiatingViewResolver's list
        of ViewResolvers is not configured explicitly, it automatically uses
        any ViewResolvers defined in the application context.
      
The corresponding controller code that returns an Atom RSS feed
      for a URI of the form http://localhost/content.atom
      or http://localhost/content with an
      Accept header of application/atom+xml is shown
      below.
      
@Controller
public class ContentController {
    private List<SampleContent> contentList = new ArrayList<SampleContent>();
    @RequestMapping(value="/content", method=RequestMethod.GET)
    public ModelAndView getContent() {
        ModelAndView mav = new ModelAndView();
        mav.setViewName("content");
        mav.addObject("sampleContentList", contentList);
        return mav;
  
17.6 Using flash attributes




    

    
Flash attributes provide a way for one request to store attributes
    intended for use in another. This is most commonly needed when redirecting
    — for example, the Post/Redirect/Get pattern. Flash
    attributes are saved temporarily before the redirect (typically in the
    session) to be made available to the request after the redirect and
    removed immediately.
    
Spring MVC has two main abstractions in support of flash attributes.
    FlashMap is used to hold flash attributes while
    FlashMapManager is used to store, retrieve,
    and manage FlashMap instances.
    
Flash attribute support is always "on" and does not need to enabled
    explicitly although if not used, it never causes HTTP session creation. On
    each request there is an "input" FlashMap with
    attributes passed from a previous request (if any) and an "output"
    FlashMap with attributes to save for a subsequent
    request. Both FlashMap instances are accessible
    from anywhere in Spring MVC through static methods in
    RequestContextUtils.
    
Annotated controllers typically do not need to work with
    FlashMap directly. Instead an
    @RequestMapping method can accept an
    argument of type RedirectAttributes and use
    it to add flash attributes for a redirect scenario. Flash attributes added
    via RedirectAttributes are automatically
    propagated to the "output" FlashMap. Similarly after the redirect
    attributes from the "input" FlashMap are
    automatically added to the Model of the
    controller serving the target URL.
    
Matching requests to flash attributes
      
The concept of flash attributes exists in many other Web
      frameworks and has proven to be exposed sometimes to concurrency issues.
      This is because by definition flash attributes are to be stored until
      the next request. However the very "next" request may not be the
      intended recipient but another asynchronous request (e.g. polling or
      resource requests) in which case the flash attributes are removed too
      early.
      
To reduce the possibility of such issues,
      RedirectView automatically "stamps"
      FlashMap instances with the path and query
      parameters of the target redirect URL. In turn the default
      FlashMapManager matches that information to
      incoming requests when looking up the "input"
      FlashMap.
      
This does not eliminate the possibility of a concurrency issue
      entirely but nevertheless reduces it greatly with information that is
      already available in the redirect URL. Therefore the use of flash
      attributes is recommended mainly for redirect scenarios .
  
17.7 Building URIs
    
Spring MVC provides a mechanism for building and encoding a URI
    using UriComponentsBuilder and
    UriComponents.
    
For example you can expand and encode a URI template string:
UriComponents uriComponents =
        UriComponentsBuilder.fromUriString("http://example.com/hotels/{hotel}/bookings/{booking}").build();
URI uri = uriComponents.expand("42", "21").encode().toUri();
    
Note that UriComponents is immutable and
    the expand() and encode()
    operations return new instances if necessary.
    
You can also expand and encode using individual URI components:
UriComponents uriComponents =
        UriComponentsBuilder.newInstance()
            .scheme("http").host("example.com").path("/hotels/{hotel}/bookings/{booking}").build()
            .expand("42", "21")
            .encode();
    
In a Servlet environment the
    ServletUriComponentsBuilder sub-class provides
    static factory methods to copy available URL information from a
    Servlet requests:
HttpServletRequest request = ...
// Re-use host, scheme, port, path and query string
// Replace the "accountId" query param
ServletUriComponentsBuilder ucb =
        ServletUriComponentsBuilder.fromRequest(request).replaceQueryParam("accountId", "{id}").build()
            .expand("123")
            .encode();
    
Alternatively, you may choose to copy a subset of the available
    information up to and including the context path:
// Re-use host, port and context path
// Append "/accounts" to the path
ServletUriComponentsBuilder ucb =
        ServletUriComponentsBuilder.fromContextPath(request).path("/accounts").build()
    
Or in cases where the DispatcherServlet is mapped
    by name (e.g. /main/*), you can also have the literal part
    of the servlet mapping included:
// Re-use host, port, context path
// Append the literal part of the servlet mapping to the path
// Append "/accounts" to the path
ServletUriComponentsBuilder ucb =
        ServletUriComponentsBuilder.fromServletMapping(request).path("/accounts").build()
    
Most parts of Spring's architecture support internationalization,
    just as the Spring web MVC framework does.
    DispatcherServlet enables you to automatically
    resolve messages using the client's locale. This is done with
    LocaleResolver objects.
    
When a request comes in, the
    DispatcherServlet looks for a locale resolver, and
    if it finds one it tries to use it to set the locale. Using the
    RequestContext.getLocale() method, you can always
    retrieve the locale that was resolved by the locale resolver.
    
In addition to automatic locale resolution, you can also attach an
    interceptor to the handler mapping (see Section 17.4.1, “Intercepting requests with a
      HandlerInterceptor” for more information on
    handler mapping interceptors) to change the locale under specific
    circumstances, for example, based on a parameter in the request.
    
Locale resolvers and interceptors are defined in the
    org.springframework.web.servlet.i18n package and are
    configured in your application context in the normal way. Here is a
    selection of the locale resolvers included in Spring.
    
17.8.1 AcceptHeaderLocaleResolver




    

      
This locale resolver inspects the
      accept-language header in the request that was sent
      by the client (e.g., a web browser). Usually this header field contains
      the locale of the client's operating system.
    
17.8.2 CookieLocaleResolver
      
This locale resolver inspects a Cookie that
      might exist on the client to see if a locale is specified. If so, it
      uses the specified locale. Using the properties of this locale resolver,
      you can specify the name of the cookie as well as the maximum age. Find
      below an example of defining a
      CookieLocaleResolver.
      
<bean id="localeResolver" class="org.springframework.web.servlet.i18n.CookieLocaleResolver">
    <property name="cookieName" value="clientlanguage"/>
    <!-- in seconds. If set to -1, the cookie is not persisted (deleted when browser shuts down) -->
    <property name="cookieMaxAge" value="100000">
</bean>
      
Table 17.4. CookieLocaleResolver properties

        
Property
Default
Description
cookieName
classname + LOCALE
The name of the cookie
cookieMaxAge
Integer.MAX_INT
The maximum time a cookie will stay persistent on the
              client. If -1 is specified, the cookie will not be persisted; it
              will only be available until the client shuts down his or her
              browser.
cookiePath
/
Limits the visibility of the cookie to a certain part of
              your site. When cookiePath is specified, the cookie will only be
              visible to that path and the paths below it.
    
17.8.3 SessionLocaleResolver
      
The SessionLocaleResolver allows you to
      retrieve locales from the session that might be associated with the
      user's request.
    
17.8.4 LocaleChangeInterceptor
      
You can enable changing of locales by adding the
      LocaleChangeInterceptor to one of the handler
      mappings (see Section 17.4, “Handler mappings”). It will detect a
      parameter in the request and change the locale. It calls
      setLocale() on the
      LocaleResolver that also exists in the
      context. The following example shows that calls to all
      *.view resources containing a parameter named
      siteLanguage will now change the locale. So, for
      example, a request for the following URL,
      http://www.sf.net/home.view?siteLanguage=nl will
      change the site language to Dutch.
      
<bean id="localeChangeInterceptor"
      class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">
    <property name="paramName" value="siteLanguage"/>
</bean>
<bean id="localeResolver"
      class="org.springframework.web.servlet.i18n.CookieLocaleResolver"/>
<bean id="urlMapping"
      class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
    <property name="interceptors">
            <ref bean="localeChangeInterceptor"/>
        </list>
    </property>
    <property name="mappings">
        <value>/**/*.view=someController</value>
    </property>
</bean>
  
17.9 Using themes
    
17.9.1 Overview of themes
      
You can apply Spring Web MVC framework themes to set the overall
      look-and-feel of your application, thereby enhancing user experience. A
      theme is a collection of static resources, typically style sheets and
      images, that affect the visual style of the application.
    
17.9.2 Defining themes
      
To use themes in your web application, you must set up an
      implementation of the
      org.springframework.ui.context.ThemeSource
      interface. The WebApplicationContext
      interface extends ThemeSource but
      delegates its responsibilities to a dedicated implementation. By default
      the delegate will be an
      org.springframework.ui.context.support.ResourceBundleThemeSource
      implementation that loads properties files from the root of the
      classpath. To use a custom ThemeSource
      implementation or to configure the base name prefix of the
      ResourceBundleThemeSource, you can register a
      bean in the application context with the reserved name
      themeSource. The web application context
      automatically detects a bean with that name and uses it.
      
When using the ResourceBundleThemeSource, a
      theme is defined in a simple properties file. The
      properties file lists the resources that make up the theme. Here is an
      example:
      
styleSheet=/themes/cool/style.css
background=/themes/cool/img/coolBg.jpg
      
The keys of the properties are the names that refer to the themed
      elements from view code. For a JSP, you typically do this using the
      spring:theme custom tag, which is very similar to the
      spring:message tag. The following JSP fragment uses
      the theme defined in the previous example to customize the look and
      feel:
      
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>
      <link rel="stylesheet" href="<spring:theme code='styleSheet'/>" type="text/css"/>
   </head>
   <body style="background=<spring:theme code='background'/>">
   </body>
</html>
      
By default, the ResourceBundleThemeSource
      uses an empty base name prefix. As a result, the properties files are
      loaded from the root of the classpath. Thus you would put the
      cool.properties theme definition in a directory at
      the root of the classpath, for example, in
      /WEB-INF/classes. The
      ResourceBundleThemeSource uses the standard Java
      resource bundle loading mechanism, allowing for full
      internationalization of themes. For example, we could have a
      /WEB-INF/classes/cool_nl.properties that references a
      special background image with Dutch text on it.
    
17.9.3 Theme resolvers
      
After you define themes, as in the preceding section, you decide
      which theme to use. The DispatcherServlet will
      look for a bean named themeResolver to find out
      which ThemeResolver implementation to
      use. A theme resolver works in much the same way as a
      LocaleResolver. It detects the theme to
      use for a particular request and can also alter the request's theme. The
      following theme resolvers are provided by Spring:
      
Table 17.5. ThemeResolver
        implementations

        
Class
Description
FixedThemeResolver
Selects a fixed theme, set using the
              defaultThemeName property.
SessionThemeResolver
The theme is maintained in the user's HTTP session. It
              only needs to be set once for each session, but is not persisted
              between sessions.
CookieThemeResolver
The selected theme is stored in a cookie on the
              client.
      
Spring also provides a
      ThemeChangeInterceptor that allows theme changes
      on every request with a simple request parameter.
  
17.10 Spring's multipart (file upload) support
    
17.10.1 Introduction
      
Spring's built-in multipart support handles file uploads in web
      applications. You enable this multipart support with pluggable
      MultipartResolver objects, defined in the
      org.springframework.web.multipart package. Spring
      provides one MultipartResolver
      implementation for use with  Commons
      FileUpload and another for use with Servlet 3.0
      multipart request parsing.
      
By default, Spring does no multipart handling, because some
      developers want to handle multiparts themselves. You enable Spring
      multipart handling by adding a multipart resolver to the web
      application's context. Each request is inspected to see if it contains a
      multipart. If no multipart is found, the request continues as expected.
      If a multipart is found in the request, the
      MultipartResolver that has been declared in your
      context is used. After that, the multipart attribute in your request is
      treated like any other attribute.
    
17.10.2 Using a MultipartResolver with
      Commons FileUpload
      
The following example shows how to use the
      CommonsMultipartResolver:
      
<bean id="multipartResolver"
    class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
    <!-- one of the properties available; the maximum file size in bytes -->
    <property name="maxUploadSize" value="100000"/>
</bean>
      
Of course you also need to put the appropriate jars in your
      classpath for the multipart resolver to work. In the case of the
      CommonsMultipartResolver, you need to use
      commons-fileupload.jar.
      
When the Spring DispatcherServlet detects a
      multi-part request, it activates the resolver that has been declared in
      your context and hands over the request. The resolver then wraps the
      current HttpServletRequest into a
      MultipartHttpServletRequest that supports
      multipart file uploads. Using the
      MultipartHttpServletRequest, you can get
      information about the multiparts contained by this request and actually
      get access to the multipart files themselves in your controllers.
    
17.10.3 Using a MultipartResolver with
      Servlet 3.0




    

      
In order to use Servlet 3.0 based multipart parsing, you need to
      mark the DispatcherServlet with a
      "multipart-config" section in
      web.xml, or with a
      javax.servlet.MultipartConfigElement in
      programmatic Servlet registration, or in case of a custom Servlet class
      possibly with a
      javax.servlet.annotation.MultipartConfig
      annotation on your Servlet class. Configuration settings such as maximum
      sizes or storage locations need to be applied at that Servlet
      registration level as Servlet 3.0 does not allow for those settings to
      be done from the MultipartResolver.
      
Once Servlet 3.0 multipart parsing has been enabled in one of the
      above mentioned ways you can add the
      StandardServletMultipartResolver to your Spring
      configuration:
      
<bean id="multipartResolver"
    class="org.springframework.web.multipart.support.StandardServletMultipartResolver">
</bean>
    
17.10.4 Handling a file upload in a form
      
After the MultipartResolver completes its
      job, the request is processed like any other. First, create a form with
      a file input that will allow the user to upload a form. The encoding
      attribute (enctype="multipart/form-data") lets the
      browser know how to encode the form as multipart request:
        <title>Upload a file please</title>
    </head>
        <h1>Please upload a file</h1>
        <form method="post" action="/form" enctype="multipart/form-data">
            <input type="text" name="name"/>
            <input type="file" name="file"/>
            <input type="submit"/>
        </form>
    </body>
</html>
      
The next step is to create a controller that handles the file
      upload. This controller is very similar to a normal annotated
      @Controller, except that we use
      MultipartHttpServletRequest or
      MultipartFile in the method parameters:
      
@Controller
public class FileUploadController {
    @RequestMapping(value = "/form", method = RequestMethod.POST)
    public String handleFormUpload(@RequestParam("name") String name,
        @RequestParam("file") MultipartFile file) {
        if (!file.isEmpty()) {
            byte[] bytes = file.getBytes();
            // store the bytes somewhere
           return "redirect:uploadSuccess";
       } else {
           return "redirect:uploadFailure";
      
Note how the @RequestParam method
      parameters map to the input elements declared in the form. In this
      example, nothing is done with the byte[], but in
      practice you can save it in a database, store it on the file system, and
      so on.
      
When using Servlet 3.0 multipart parsing you can also use
      javax.servlet.http.Part for the method
      parameter:
      
@Controller
public class FileUploadController {
    @RequestMapping(value = "/form", method = RequestMethod.POST)
    public String handleFormUpload(@RequestParam("name") String name,
        @RequestParam("file") Part file) {
        InputStream inputStream = file.getInputStream();
        // store bytes from uploaded file somewhere
        return "redirect:uploadSuccess";
    
17.10.5 Handling a file upload request from programmatic clients
      
Multipart requests can also be submitted from non-browser clients
      in a RESTful service scenario. All of the above examples and
      configuration apply here as well. However, unlike browsers that
      typically submit files and simple form fields, a programmatic client can
      also send more complex data of a specific content type — for example a
      multipart request with a file and second part with JSON formatted data:
      
POST /someUrl
Content-Type: multipart/mixed
--edt7Tfrdusa7r3lNQc79vXuhIIMlatb7PQg7Vp
Content-Disposition: form-data; name="meta-data"
Content-Type: application/json; charset=UTF-8
Content-Transfer-Encoding: 8bit
  "name": "value"
--edt7Tfrdusa7r3lNQc79vXuhIIMlatb7PQg7Vp
Content-Disposition: form-data; name="file-data"; filename="file.properties"
Content-Type: text/xml
Content-Transfer-Encoding: 8bit
... File Data ...
      
You could access the part named "meta-data" with a
      @RequestParam("meta-data") String
      metadata controller method argument. However, you would
      probably prefer to accept a strongly typed object initialized from the
      JSON formatted data in the body of the request part, very similar to the
      way @RequestBody converts the body of a
      non-multipart request to a target object with the help of an
      HttpMessageConverter.
      
You can use the @RequestPart
      annotation instead of the @RequestParam
      annotation for this purpose. It allows you to have the content of a
      specific multipart passed through an
      HttpMessageConverter taking into consideration
      the 'Content-Type' header of the multipart:
      
@RequestMapping(value="/someUrl", method = RequestMethod.POST)
public String onSubmit(@RequestPart("meta-data") MetaData metadata,
                       @RequestPart("file-data") MultipartFile file) {
    // ...
      
Notice how MultipartFile method arguments
      can be accessed with @RequestParam or
      with @RequestPart interchangeably.
      However, the @RequestPart("meta-data") MetaData
      method argument in this case is read as JSON content based on its
      'Content-Type' header and converted with the help of
      the MappingJackson2HttpMessageConverter.
  
17.11 Handling exceptions
    
17.11.1 HandlerExceptionResolver
      
Spring HandlerExceptionResolver implementations
      deal with unexpected exceptions that occur during controller execution.
      A HandlerExceptionResolver somewhat resembles the
      exception mappings you can define in the web application descriptor
      web.xml. However, they provide a more flexible way to
      do so. For example they provide information about which handler was
      executing when the exception was thrown. Furthermore, a programmatic way
      of handling exceptions gives you more options for responding
      appropriately before the request is forwarded to another URL (the same
      end result as when you use the Servlet specific exception
      mappings).
      
Besides implementing the
      HandlerExceptionResolver interface, which
      is only a matter of implementing the
      resolveException(Exception, Handler) method and
      returning a ModelAndView, you may also use the provided
      SimpleMappingExceptionResolver or create
      @ExceptionHandler methods.
      The SimpleMappingExceptionResolver
      enables you to take the class name of any exception that might be thrown
      and map it to a view name. This is functionally equivalent to the
      exception mapping feature from the Servlet API, but it is also possible
      to implement more finely grained mappings of exceptions from different
      handlers. The @ExceptionHandler annotation on
      the other hand can be used on methods that should be invoked to handle an
      exception. Such methods may be defined locally within an
      @Controller or may apply globally to all
      @RequestMapping methods when defined within
      an @ControllerAdvice class.
      The following sections explain this in more detail.
    
17.11.2 @ExceptionHandler
      
The HandlerExceptionResolver interface
      and the SimpleMappingExceptionResolver implementations
      allow you to map Exceptions to specific views declaratively along with some
      optional Java logic before forwarding to those views. However, in some cases,
      especially when relying on @ResponseBody methods
      rather than on view resolution, it may be more convenient to directly set the
      status of the response and optionally write error content to the body of the
      response.
      
You can do that with @ExceptionHandler
      methods. When declared within a controller such methods apply to exceptions
      raised by @RequestMapping methods of that
      contoroller (or any of its sub-classes). You can also declare an
      @ExceptionHandler method within an
      @ControllerAdvice class in which case it
      handles exceptions from @RequestMapping
      methods from any controller.
      The @ControllerAdvice annotation is
      a component annotation, which can be used with classpath scanning. It is
      automatically enabled when using the MVC namespace and the MVC Java config,
      or otherwise depending on whether the
      ExceptionHandlerExceptionResolver is configured or not.
      Below is an example of a controller-local
      @ExceptionHandler method:
      
@Controller
public class SimpleController {
  // @RequestMapping methods omitted ...
  @ExceptionHandler(IOException.class)
  public ResponseEntity<String> handleIOException(IOException ex) {
    // prepare responseEntity
    return responseEntity;
      
The @ExceptionHandler value can be set to
      an array of Exception types. If an exception is thrown that matches one of
      the types in the list, then the method annotated with the matching
      @ExceptionHandler will be invoked. If the
      annotation value is not set then the exception types listed as method
      arguments are used.
      
Much like standard controller methods annotated with a
      @RequestMapping annotation, the method arguments
      and return values of @ExceptionHandler methods
      can be flexible. For example, the
      HttpServletRequest can be accessed in Servlet
      environments and the PortletRequest in Portlet
      environments. The return type can be a String,
      which is interpreted as a view name, a
      ModelAndView object, a
      ResponseEntity, or you can also add the
      @ResponseBody to have the method return value
      converted with message converters and written to the response stream.
    
17.11.3 Handling Standard Spring MVC Exceptions




    

      
Spring MVC may raise a number of exceptions while processing
      a request. The SimpleMappingExceptionResolver can easily
      map any exception to a default error view as needed.
      However, when working with clients that interpret responses in an automated
      way you will want to set specific status code on the response. Depending on
      the exception raised the status code may indicate a client error (4xx) or a
      server error (5xx).
      
The DefaultHandlerExceptionResolver translates
      Spring MVC exceptions to specific error status codes. It is registered
      by default with the MVC namespace, the MVC Java config, and also by the
      the DispatcherServlet (i.e. when not using the MVC
      namespace or Java config). Listed below are some of the exceptions handled
      by this resolver and the corresponding status codes:
          
Exception
HTTP Status Code
BindException
400 (Bad Request)
ConversionNotSupportedException
500 (Internal Server Error)
HttpMediaTypeNotAcceptableException
406 (Not Acceptable)
HttpMediaTypeNotSupportedException
415 (Unsupported Media Type)
HttpMessageNotReadableException
400 (Bad Request)
HttpMessageNotWritableException
500 (Internal Server Error)
HttpRequestMethodNotSupportedException
405 (Method Not Allowed)
MethodArgumentNotValidException
400 (Bad Request)
MissingServletRequestParameterException
400 (Bad Request)
MissingServletRequestPartException
400 (Bad Request)
NoSuchRequestHandlingMethodException
404 (Not Found)
TypeMismatchException
400 (Bad Request)

        
The DefaultHandlerExceptionResolver works
        transparently by setting the status of the response. However, it stops short
        of writing any error content to the body of the response while your
        application may need to add developer-friendly content to every error
        response for example when providing a REST API. You can prepare a
        ModelAndView and
        render error content through view resolution -- i.e. by configuring a
        ContentNegotiatingViewResolver,
        MappingJacksonJsonView, and so on. However, you
        may prefer to use @ExceptionHandler
        methods instead.
        
If you prefer to write error content via
        @ExceptionHandler methods you can extend
        ResponseEntityExceptionHandler instead.
        This is a convenient base for @ControllerAdvice
        classes providing an @ExceptionHandler
        method to handle standard Spring MVC exceptions and return
        ResponseEntity. That allows you to customize the response
        and write error content with message converters. See the Javadoc of
        ResponseEntityExceptionHandler for more details.
    
17.11.4 Annotating Business Exceptions With @ResponseStatus
      
A business exception can be annotated with
      @ResponseStatus. When the exception is raised,
      the ResponseStatusExceptionResolver handles it by
      setting the status of the response accordingly.
      By default the DispatcherServlet registers
      the ResponseStatusExceptionResolver and it is
      available for use.
    
17.11.5 Customizing the Default Servlet Container Error Page
        
When the status of the response is set to an error status code
        and the body of the response is empty, Servlet containers commonly render
        an HTML formatted error page.
        To customize the default error page of the container, you can
        declare an <error-page> element in
        web.xml. Up until Servlet 3, that element had to
        be mapped to a specific status code or exception type. Starting with
        Servlet 3 an error page does not need to be mapped, which effectively
        means the specified location customizes the default Servlet container
        error page.
      
<error-page>
    <location>/error</location>
</error-page>
        
Note that the actual location for the error page can be a
        JSP page or some other URL within the container including one handled
        through an @Controller method:
        
When writing error information, the status code and the error message
        set on the HttpServletResponse can be
        accessed through request attributes in a controller:
@Controller
public class ErrorController {
    @RequestMapping(value="/error", produces="application/json")
    @ResponseBody
    public Map<String, Object> handle(HttpServletRequest request) {
        Map<String, Object> map = new HashMap<String, Object>();
        map.put("status", request.getAttribute("javax.servlet.error.status_code"));
        map.put("reason", request.getAttribute("javax.servlet.error.message"));
        return map;
        
or in a JSP:
      
<%@ page contentType="application/json" pageEncoding="UTF-8"%>
   status:<%=request.getAttribute("javax.servlet.error.status_code") %>,
   reason:<%=request.getAttribute("javax.servlet.error.message") %>
    
For a lot of projects, sticking to established conventions and
    having reasonable defaults is just what they (the projects) need, and
    Spring Web MVC now has explicit support for convention over
    configuration. What this means is that if you establish a set
    of naming conventions and suchlike, you can
    substantially cut down on the amount of configuration
    that is required to set up handler mappings, view resolvers,
    ModelAndView instances, etc. This is a great boon
    with regards to rapid prototyping, and can also lend a degree of (always
    good-to-have) consistency across a codebase should you choose to move
    forward with it into production.
    
Convention-over-configuration support addresses the three core areas
    of MVC: models, views, and controllers.
    
17.12.1 The Controller
      ControllerClassNameHandlerMapping
      
The ControllerClassNameHandlerMapping class
      is a HandlerMapping implementation that
      uses a convention to determine the mapping between request URLs and the
      Controller instances that are to handle
      those requests.
      
Consider the following simple
      Controller implementation. Take special
      notice of the name of the class.
      
public class ViewShoppingCartController implements Controller {
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
        // the implementation is not hugely important for this example...
      
Here is a snippet from the corresponding Spring Web MVC
      configuration file:
      
<bean class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/>
<bean id="viewShoppingCart" class="x.y.z.ViewShoppingCartController">
    <!-- inject dependencies as required... -->
</bean>
      
The ControllerClassNameHandlerMapping finds
      all of the various handler (or
      Controller) beans defined in its
      application context and strips Controller off the
      name to define its handler mappings. Thus,
      ViewShoppingCartController maps to the
      /viewshoppingcart* request URL.
      
Let's look at some more examples so that the central idea becomes
      immediately familiar. (Notice all lowercase in the URLs, in contrast to
      camel-cased Controller class
      names.)
          
WelcomeController maps to the
          /welcome* request URL
          
HomeController maps to the
          /home* request URL
          
IndexController maps to the
          /index* request URL
          
RegisterController maps to the
          /register* request URL
      
In the case of MultiActionController
      handler classes, the mappings generated are slightly more complex. The
      Controller names in the following
      examples are assumed to be MultiActionController
      implementations:
          
AdminController maps to the
          /admin/* request URL
          
CatalogController maps to the
          /catalog/* request URL
      
If you follow the convention of naming your
      Controller implementations as
      xxxController, the
      ControllerClassNameHandlerMapping saves you the
      tedium of defining and maintaining a potentially
      looooong
      SimpleUrlHandlerMapping (or suchlike).
      
The ControllerClassNameHandlerMapping class
      extends the AbstractHandlerMapping base class so
      you can define HandlerInterceptor
      instances and everything else just as you would with many other
      HandlerMapping implementations.
    
17.12.2 The Model ModelMap
      (ModelAndView)




    

      
The ModelMap class is essentially a
      glorified Map that can make adding
      objects that are to be displayed in (or on) a
      View adhere to a common naming
      convention. Consider the following
      Controller implementation; notice that
      objects are added to the ModelAndView without any
      associated name specified.
      
public class DisplayShoppingCartController implements Controller {
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
        List cartItems = // get a List of CartItem objects
        User user = // get the User doing the shopping
        ModelAndView mav = new ModelAndView("displayShoppingCart"); <-- the logical view name
        mav.addObject(cartItems); <-- look ma, no name, just the object
        mav.addObject(user); <-- and again ma!
        return mav;
      
The ModelAndView class uses a
      ModelMap class that is a custom
      Map implementation that automatically
      generates a key for an object when an object is added to it. The
      strategy for determining the name for an added object is, in the case of
      a scalar object such as User, to use the short
      class name of the object's class. The following examples are names that
      are generated for scalar objects put into a
      ModelMap instance.
          
An x.y.User instance added will have
          the name user generated.
          
An x.y.Registration instance added will
          have the name registration generated.
          
An x.y.Foo instance added will have the
          name foo generated.
          
A java.util.HashMap instance added will
          have the name hashMap generated. You probably
          want to be explicit about the name in this case because
          hashMap is less than intuitive.
          
Adding null will result in an
          IllegalArgumentException being thrown. If the
          object (or objects) that you are adding could be
          null, then you will also want to be explicit
          about the name.
      
What, no automatic pluralization?
        
Spring Web MVC's convention-over-configuration support does not
        support automatic pluralization. That is, you cannot add a
        List of Person
        objects to a ModelAndView and have the
        generated name be people.
        
This decision was made after some debate, with the
        “Principle of Least Surprise” winning out in the
      
The strategy for generating a name after adding a
      Set or a
      List is to peek into the collection, take
      the short class name of the first object in the collection, and use that
      with List appended to the name. The same applies to
      arrays although with arrays it is not necessary to peek into the array
      contents. A few examples will make the semantics of name generation for
      collections clearer:
          
An x.y.User[] array with zero or more
          x.y.User elements added will have the name
          userList generated.
          
An x.y.Foo[] array with zero or more
          x.y.User elements added will have the name
          fooList generated.
          
A java.util.ArrayList with one or more
          x.y.User elements added will have the name
          userList generated.
          
A java.util.HashSet with one or more
          x.y.Foo elements added will have the name
          fooList generated.
          
An empty
          java.util.ArrayList will not be added at all
          (in effect, the addObject(..) call will
          essentially be a no-op).
    
17.12.3 The View -
      RequestToViewNameTranslator
      
The RequestToViewNameTranslator
      interface determines a logical View name
      when no such logical view name is explicitly supplied. It has just one
      implementation, the
      DefaultRequestToViewNameTranslator class.
      
The DefaultRequestToViewNameTranslator maps
      request URLs to logical view names, as with this example:
      
public class RegistrationController implements Controller {
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) {
        // process the request...
        ModelAndView mav = new ModelAndView();
        // add data as necessary to the model...
        return mav;
        // notice that no View or logical view name has been set
      
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!-- this bean with the well known name generates view names for us -->
    <bean id="viewNameTranslator"
        class="org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator"/>
    <bean class="x.y.RegistrationController">
        <!-- inject dependencies as necessary -->
    </bean>
    <!-- maps request URLs to Controller names -->
    <bean class="org.springframework.web.servlet.mvc.support.ControllerClassNameHandlerMapping"/>
    <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
    </bean>
</beans>
      
Notice how in the implementation of the
      handleRequest(..) method no
      View or logical view name is ever set on
      the ModelAndView that is returned. The
      DefaultRequestToViewNameTranslator is tasked with
      generating a logical view name from the URL of the
      request. In the case of the above
      RegistrationController, which is used in
      conjunction with the
      ControllerClassNameHandlerMapping, a request URL
      of http://localhost/registration.html results in a
      logical view name of registration being generated by
      the DefaultRequestToViewNameTranslator. This
      logical view name is then resolved into the
      /WEB-INF/jsp/registration.jsp view by the
      InternalResourceViewResolver bean.
        
You do not need to define a
        DefaultRequestToViewNameTranslator bean
        explicitly. If you like the default settings of the
        DefaultRequestToViewNameTranslator, you can
        rely on the Spring Web MVC DispatcherServlet to
        instantiate an instance of this class if one is not explicitly
        configured.
      
Of course, if you need to change the default settings, then you do
      need to configure your own
      DefaultRequestToViewNameTranslator bean
      explicitly. Consult the comprehensive Javadoc for the
      DefaultRequestToViewNameTranslator class for
      details of the various properties that can be configured.
  
17.13 ETag support
    
An ETag
    (entity tag) is an HTTP response header returned by an HTTP/1.1 compliant
    web server used to determine change in content at a given URL. It can be
    considered to be the more sophisticated successor to the
    Last-Modified header. When a server returns a
    representation with an ETag header, the client can use this header in
    subsequent GETs, in an If-None-Match header. If the
    content has not changed, the server returns 304: Not
    Modified.
    
Support for ETags is provided by the Servlet filter
    ShallowEtagHeaderFilter. It is a plain Servlet
    Filter, and thus can be used in combination with any web framework. The
    ShallowEtagHeaderFilter filter creates so-called
    shallow ETags (as opposed to deep ETags, more about that later).The
    filter caches the content of the rendered JSP (or other content),
    generates an MD5 hash over that, and returns that as an ETag header in the
    response. The next time a client sends a request for the same resource, it
    uses that hash as the If-None-Match value. The filter
    detects this, renders the view again, and compares the two hashes. If they
    are equal, a 304 is returned. This filter will not save
    processing power, as the view is still rendered. The only thing it saves
    is bandwidth, as the rendered response is not sent back over the
    wire.
    
You configure the ShallowEtagHeaderFilter in
    web.xml:
    
<filter>
  <filter-name>etagFilter</filter-name>
    <filter-class>org.springframework.web.filter.ShallowEtagHeaderFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>etagFilter</filter-name>
  <servlet-name>petclinic</servlet-name>
</filter-mapping>
  
17.14 Code-based Servlet container initialization
    
In a Servlet 3.0+ environment, you  have the option of configuring the
    Servlet container programmatically as an alternative or in combination with
    a web.xml file.
    Below is an example of registering a DispatcherServlet:
    
import org.springframework.web.WebApplicationInitializer;
public class MyWebApplicationInitializer implements WebApplicationInitializer {
    @Override
    public void onStartup(ServletContext container) {
        XmlWebApplicationContext appContext = new XmlWebApplicationContext();
        appContext.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");
        ServletRegistration.Dynamic registration = container.addServlet("dispatcher", new DispatcherServlet(appContext));
        registration.setLoadOnStartup(1);
        registration.addMapping("/");
    
WebApplicationInitializer is an interface
    provided by Spring MVC that ensures your implementation is detected and
    automatically used to initialize any Servlet 3 container. An abstract base
    class implementation of WebApplicationInitializer named
    AbstractDispatcherServletInitializer makes it even
    easier to register the DispatcherServlet by simply overriding
    methods to specify the servlet mapping and the location of the
    DispatcherServlet configuration:
    
public class MyWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {
    @Override
    protected Class<?>[] getRootConfigClasses() {
        return null;
    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class[] { MyWebConfig.class };
    @Override
    protected String[] getServletMappings() {
        return new String[] { "/" };
    
The above example is for an application that uses Java-based Spring
    configuration. If using XML-based Spring configuration, extend directly from
    AbstractDispatcherServletInitializer:
    
public class MyWebAppInitializer extends AbstractDispatcherServletInitializer {
    @Override
    protected WebApplicationContext createRootApplicationContext() {
        return null;
    @Override
    protected WebApplicationContext createServletApplicationContext() {
        XmlWebApplicationContext cxt = new XmlWebApplicationContext();
        cxt.setConfigLocation("/WEB-INF/spring/dispatcher-config.xml");
        return cxt;
    @Override
    protected String[] getServletMappings() {
        return new String[] { "/" };
    
AbstractDispatcherServletInitializer also provides
    a convenient way to add Filter instances
    and have them automatically mapped to the DispatcherServlet:
    
public class MyWebAppInitializer extends AbstractDispatcherServletInitializer {
    // ...
    @Override
    protected Filter[] getServletFilters() {
        return new Filter[] { new HiddenHttpMethodFilter(), new CharacterEncodingFilter() };
    
Each filter is added with a default name based on its concrete type and
    automatically mapped to the DispatcherServlet.
    
The isAsyncSupported protected method of
    AbstractDispatcherServletInitializer provides
    a single place to enable async support on the DispatcherServlet
    and all filters mapped to it. By default this flag is set to true.
  
17.15 Configuring Spring MVC




    

    
Section 17.2.1, “Special Bean Types In the WebApplicationContext” and
    Section 17.2.2, “Default DispatcherServlet Configuration” explained about
    Spring MVC's special beans and the default implementations
    used by the DispatcherServlet.
    In this section you'll learn about two additional ways of
    configuring Spring MVC. Namely the MVC Java config and
    the MVC XML namespace.
    
The MVC Java config and the MVC namespace provide
    similar default configuration that overrides
    the DispatcherServlet defaults.
    The goal is to spare most applications from having to
    having to create the same configuration and also to
    provide higher-level constructs for configuring
    Spring MVC that serve as a simple starting point and
    require little or no prior knowledge of the underlying
    configuration.
    
You can choose either the MVC Java config or the
    MVC namespace depending on your preference. Also as you
    will see further below, with the MVC Java config it is
    easier to see the underlying configuration as well as
    to make fine-grained customizations directly to the
    created Spring MVC beans.
    But let's start from the beginning.
    
17.15.1 Enabling the MVC Java Config or the MVC XML Namespace
        
To enable MVC Java config add the annotation
        @EnableWebMvc to one of your
        @Configuration classes:
        
@Configuration
@EnableWebMvc
public class WebConfig {
        
To achieve the same in XML use the mvc:annotation-driven element:
        
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">
    <mvc:annotation-driven />
</beans>
      
The above registers a
      RequestMappingHandlerMapping, a
      RequestMappingHandlerAdapter, and an
      ExceptionHandlerExceptionResolver (among others)
      in support of processing requests with annotated controller methods using
      annotations such as @RequestMapping ,
      @ExceptionHandler, and others.
      
It also enables the following:
            
Spring 3 style type conversion through a ConversionService instance
            in addition to the JavaBeans PropertyEditors used for Data Binding.
            
Support for formatting Number
            fields using the @NumberFormat
            annotation through the
            ConversionService.
            
Support for formatting Date,
            Calendar, Long, and Joda Time fields using the
            @DateTimeFormat
            annotation.
            
Support for validating @Controller
            inputs with @Valid,
            if a JSR-303 Provider is present on the classpath.
            
HttpMessageConverter support for
            @RequestBody method
            parameters and @ResponseBody
            method return values from
            @RequestMapping or
            @ExceptionHandler methods.
            
This is the complete list of HttpMessageConverters set up by
            mvc:annotation-driven: 

                  
ByteArrayHttpMessageConverter
                  converts byte arrays.
                  
StringHttpMessageConverter
                  converts strings.
                  
ResourceHttpMessageConverter
                  converts to/from
                  org.springframework.core.io.Resource
                  for all media types.
                  
SourceHttpMessageConverter
                  converts to/from a
                  javax.xml.transform.Source.
                  
FormHttpMessageConverter
                  converts form data to/from a
                  MultiValueMap<String,
                  String>.
                  
Jaxb2RootElementHttpMessageConverter
                  converts Java objects to/from XML — added if JAXB2 is
                  present on the classpath.
                  
MappingJackson2HttpMessageConverter
                  (or MappingJacksonHttpMessageConverter)
                  converts to/from JSON — added if Jackson 2 (or Jackson) is present
                  on the classpath.
                  
AtomFeedHttpMessageConverter
                  converts Atom feeds — added if Rome is present on the
                  classpath.
                  
RssChannelHttpMessageConverter
                  converts RSS feeds — added if Rome is present on the
                  classpath.
        
To customize the default configuration in Java you simply
        implement the WebMvcConfigurer
        interface or more likely extend the class
        WebMvcConfigurerAdapter and override
        the methods you need. Below is an example of some of the available
        methods to override. See WebMvcConifgurer for
        a list of all methods and the Javadoc for further details:
        
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  protected void addFormatters(FormatterRegistry registry) {
    // Add formatters and/or converters
  @Override
  public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    // Configure the list of HttpMessageConverters to use
        
To customize the default configuration of
        <mvc:annotation-driven /> check what
        attributes and sub-elements it supports. You can view the
        Spring MVC XML schema
        or use the code completion feature of your IDE to discover
        what attributes and sub-elements are available.
        The sample below shows a subset of what is available:
        
<mvc:annotation-driven conversion-service="conversionService">
    <mvc:message-converters>
        <bean class="org.example.MyHttpMessageConverter"/>
        <bean class="org.example.MyOtherHttpMessageConverter"/>
    </mvc:message-converters>
</mvc:annotation-driven>
<bean id="conversionService" class="org.springframework.format.support.FormattingConversionServiceFactoryBean">
    <property name="formatters">
            <bean class="org.example.MyFormatter"/>
            <bean class="org.example.MyOtherFormatter"/>
        </list>
    </property>
</bean>
    
17.15.3 Configuring Interceptors
      
You can configure HandlerInterceptors
      or WebRequestInterceptors to be applied
      to all incoming requests or restricted to specific URL path patterns.
      
An example of registering interceptors in Java:
      
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  public void addInterceptors(InterceptorRegistry registry) {
    registry.addInterceptor(new LocaleInterceptor());
    registry.addInterceptor(new ThemeInterceptor()).addPathPatterns("/**").excludePathPatterns("/admin/**");
    registry.addInterceptor(new SecurityInterceptor()).addPathPatterns("/secure/*");
      
And in XML use the <mvc:interceptors> element:
      
<mvc:interceptors>
    <bean class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor" />
    <mvc:interceptor>
        <mapping path="/**"/>
        <exclude-mapping path="/admin/**"/>
        <bean class="org.springframework.web.servlet.theme.ThemeChangeInterceptor" />
    </mvc:interceptor>
    <mvc:interceptor>
        <mapping path="/secure/*"/>
        <bean class="org.example.SecurityInterceptor" />
    </mvc:interceptor>
</mvc:interceptors>
      
Staring with Spring Framework 3.2, you can configure how Spring MVC
      determines the requested media types from the client for request mapping
      as well as for content negotiation purposes. The available options are
      to check the file extension in the request URI, the "Accept" header,
      a request parameter, as well as to fall back on a default content type.
      By default, file extension in the request URI is checked first and
      the "Accept" header is checked next.
      
For file extensions in the request URI, the MVC Java config and
      the MVC namespace, automatically register extensions such as
      .json, .xml,
      .rss, and .atom if the
      corresponding dependencies such as Jackson, JAXB2, or Rome
      are present on the classpath. Additional extensions may be not need
      to be registered explicitly if they can be discovered via
      ServletContext.getMimeType(String) or the
      Java Activation Framework
      (see javax.activation.MimetypesFileTypeMap).
      
Below is an example of customizing content negotiation
      options through the MVC Java config:
      
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
    configurer.favorPathExtension(false).favorParameter(true);
     
In the MVC namespace, the <mvc:annotation-driven> element
     has a content-negotiation-manager attribute, which expects a
     ContentNegotiationManager that in turn can be created
     with a ContentNegotiationManagerFactoryBean:
     
<mvc:annotation-driven content-negotiation-manager="contentNegotiationManager" />
<bean id="contentNegotiationManager" class="org.springframework.web.accept.ContentNegotiationManagerFactoryBean">
    <property name="favorPathExtension" value="false" />
    <property name="favorParameter" value="true" />
    <property name="mediaTypes" >
        <value>
            json=application/json
            xml=application/xml
        </value>
    </property>
</bean>
      
If not using the MVC Java config or the MVC namespace, you'll need
      to create an instance of ContentNegotiationManager
      and use it to configure
      RequestMappingHandlerMapping for request mapping
      purposes, and RequestMappingHandlerAdapter and
      ExceptionHandlerExceptionResolver for
      content negotiation purposes.
      
Note that ContentNegotiatingViewResolver
      now can also be configured with a ContentNegotiationManager,
      so you can use one instance throughout Spring MVC.
      
In more advanced cases, it may be useful to configure
      multiple ContentNegotiationManager instances
      that in turn may contain custom
      ContentNegotiationStrategy implementations.
      For example you could configure
      ExceptionHandlerExceptionResolver with
      a ContentNegotiationManager that always
      resolves the requested media type to "application/json".
      Or you may want to plug a custom strategy that has some logic to select
      a default content type (e.g. either XML or JSON) if no content
      types were requested.
    
17.15.5 Configuring View Controllers




    

      
This is a shortcut for defining a
      ParameterizableViewController that immediately
      forwards to a view when invoked. Use it in static cases when there is no
      Java controller logic to execute before the view generates the
      response.
      
An example of forwarding a request for "/"
      to a view called "home" in Java:
      
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  public void addViewControllers(ViewControllerRegistry registry) {
    registry.addViewController("/").setViewName("home");
      
And the same in XML use the <mvc:view-controller> element:
      
<mvc:view-controller path="/" view-name="home"/>
    
17.15.6 Configuring Serving of Resources
      
This option allows static resource requests following a particular
      URL pattern to be served by a
      ResourceHttpRequestHandler from any of a list of
      Resource locations. This provides a convenient
      way to serve static resources from locations other than the web
      application root, including locations on the classpath. The
      cache-period property may be used to set far future
      expiration headers (1 year is the recommendation of optimization tools
      such as Page Speed and YSlow) so that they will be more efficiently
      utilized by the client. The handler also properly evaluates the
      Last-Modified header (if present) so that a
      304 status code will be returned as appropriate, avoiding
      unnecessary overhead for resources that are already cached by the
      client. For example, to serve resource requests with a URL pattern of
      /resources/** from a public-resources
      directory within the web application root you would use:
      
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry.addResourceHandler("/resources/**").addResourceLocations("/public-resources/");
      
And the same in XML:
      
<mvc:resources mapping="/resources/**" location="/public-resources/"/>
      
To serve these resources with a 1-year future expiration to ensure
      maximum use of the browser cache and a reduction in HTTP requests made
      by the browser:
      
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry.addResourceHandler("/resources/**").addResourceLocations("/public-resources/").setCachePeriod(31556926);
      
And in XML:
      
<mvc:resources mapping="/resources/**" location="/public-resources/" cache-period="31556926"/>
      
The mapping attribute must be an Ant pattern that can
      be used by SimpleUrlHandlerMapping, and the
      location attribute must specify one or more valid resource
      directory locations. Multiple resource locations may be specified using
      a comma-separated list of values. The locations specified will be
      checked in the specified order for the presence of the resource for any
      given request. For example, to enable the serving of resources from both
      the web application root and from a known path of
      /META-INF/public-web-resources/ in any jar on the
      classpath use:
      
@EnableWebMvc
@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry.addResourceHandler("/resources/**")
      .addResourceLocations("/", "classpath:/META-INF/public-web-resources/");
      
And in XML:
      
<mvc:resources mapping="/resources/**" location="/, classpath:/META-INF/public-web-resources/"/>
      
When serving resources that may change when a new version of the
      application is deployed, it is recommended that you incorporate a
      version string into the mapping pattern used to request the resources,
      so that you may force clients to request the newly deployed version of
      your application's resources. Such a version string can be parameterized
      and accessed using SpEL so that it may be easily managed in a single
      place when deploying new versions.
      
As an example, let's consider an application that uses a
      performance-optimized custom build (as recommended) of the Dojo
      JavaScript library in production, and that the build is generally
      deployed within the web application at a path of
      /public-resources/dojo/dojo.js. Since different parts of
      Dojo may be incorporated into the custom build for each new version of
      the application, the client web browsers need to be forced to
      re-download that custom-built dojo.js resource any time a
      new version of the application is deployed. A simple way to achieve this
      would be to manage the version of the application in a properties file,
      such as:
      
application.version=1.0.0
      
and then to make the properties file's values accessible to SpEL
      as a bean using the util:properties tag:
      
<util:properties id="applicationProps" location="/WEB-INF/spring/application.properties"/>
      
With the application version now accessible via SpEL, we can
      incorporate this into the use of the resources tag:
      
<mvc:resources mapping="/resources-#{applicationProps['application.version']}/**" location="/public-resources/"/>
      
In Java, you can use the @PropertySouce
      annotation and then inject the Environment
      abstraction for access to all defined properties:
      
@Configuration
@EnableWebMvc
@PropertySource("/WEB-INF/spring/application.properties")
public class WebConfig extends WebMvcConfigurerAdapter {
  @Inject Environment env;
  @Override
  public void addResourceHandlers(ResourceHandlerRegistry registry) {
    registry.addResourceHandler("/resources-" + env.getProperty("application.version") + "/**")
      .addResourceLocations("/public-resources/");
      
and finally, to request the resource with the proper URL, we can
      take advantage of the Spring JSP tags:
      
<spring:eval expression="@applicationProps['application.version']" var="applicationVersion"/>
<spring:url value="/resources-{applicationVersion}" var="resourceUrl">
    <spring:param name="applicationVersion" value="${applicationVersion}"/>
</spring:url>
<script src="${resourceUrl}/dojo/dojo.js" type="text/javascript"> </script>
    
17.15.7 mvc:default-servlet-handler
      
This tag allows for mapping the DispatcherServlet to
      "/" (thus overriding the mapping of the container's default Servlet),
      while still allowing static resource requests to be handled by the
      container's default Servlet. It configures a
      DefaultServletHttpRequestHandler with a URL mapping of
      "/**" and the lowest priority relative to other URL mappings.
      
This handler will forward all requests to the default Servlet.
      Therefore it is important that it remains last in the order of all other
      URL HandlerMappings. That will be the case if you use
      <mvc:annotation-driven> or alternatively if you are
      setting up your own customized HandlerMapping instance be
      sure to set its order property to a value lower than that
      of the DefaultServletHttpRequestHandler, which is
      Integer.MAX_VALUE.
      
To enable the feature using the default setup use:
      
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
    configurer.enable();
      
Or in XML:
      
<mvc:default-servlet-handler/>
      
The caveat to overriding the "/" Servlet mapping is that the
      RequestDispatcher for the default Servlet must be retrieved
      by name rather than by path. The
      DefaultServletHttpRequestHandler will attempt to
      auto-detect the default Servlet for the container at startup time, using
      a list of known names for most of the major Servlet containers
      (including Tomcat, Jetty, GlassFish, JBoss, Resin, WebLogic, and
      WebSphere). If the default Servlet has been custom configured with a
      different name, or if a different Servlet container is being used where
      the default Servlet name is unknown, then the default Servlet's name
      must be explicitly provided as in the following example:
      
@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {
  @Override
  public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
    configurer.enable("myCustomDefaultServlet");
      
Or in XML:
      
<mvc:default-servlet-handler default-servlet-name="myCustomDefaultServlet"/>
    
17.15.8 More Spring Web MVC Resources
      
See the following links and pointers for more resources about Spring Web MVC:
          
There are many excellent articles and tutorials that show how to
          build web applications with Spring MVC. Read them at the Spring
          Documentation page.
          
“Expert Spring Web MVC and Web Flow” by Seth Ladd
          and others (published by Apress) is an excellent hard copy source of
          Spring Web MVC goodness.
    
17.15.9 Advanced Customizations with MVC Java Config
      
As you can see from the above examples, MVC Java config and
      the MVC namespace provide higher level constructs that do not
      require deep knowledge of the underlying beans created for you.
      Instead it helps you to focus on your application needs.
      However, at some point you may need more fine-grained control
      or you may simply wish to understand the underlying configuration.
      
The first step towards more fine-grained control is to see the
      underlying beans created for you. In MVC Java config you can
      see the Javadoc and the @Bean
      methods in WebMvcConfigurationSupport.
      The configuration in this class is automatically imported
      through the @EnableWebMvc annotation.
      In fact if you open @EnableWebMvc you can
      see the @Import statement.
      
The next step towards more fine-grained control is to
      customize a property on one of the beans created in
      WebMvcConfigurationSupport or perhaps
      to provide your own instance. This requires two things --
      remove the @EnableWebMvc
      annotation in order to prevent the import and then
      extend directly from WebMvcConfigurationSupport.
      Here is an example:
      
@Configuration
public class WebConfig extends WebMvcConfigurationSupport {
  @Override
  public void addInterceptors(InterceptorRegistry registry){
    // ...
  @Override
  @Bean
  public RequestMappingHandlerAdapter requestMappingHandlerAdapter() {
      // Create or let "super" create the adapter
      // Then customize one of its properties
      
Note that modifying beans in this way does not prevent
      you from using any of the higher-level constructs shown earlier in
      this section. 
    
17.15.10 Advanced Customizations with the MVC Namespace
      
Fine-grained control over the configuration created for
      you is a bit harder with the MVC namespace.
      
If you do need to do that, rather than replicating the
      configuration it provides, consider configuring a
      BeanPostProcessor that detects
      the bean you want to customize by type and then modifying its
      properties as necessary. For example:
    
@Component
public class MyPostProcessor implements BeanPostProcessor {
  public Object postProcessBeforeInitialization(Object bean, String name) throws BeansException {
    if (bean instanceof RequestMappingHandlerAdapter) {
      // Modify properties of the adapter
      
Note that MyPostProcessor needs to be
      included in an <component scan />
      in order for it to be detected or if you prefer you can declare it
      explicitly with an XML bean declaration.