General utility methods for working with annotations, handling bridge methods
(which the compiler generates for generic declarations) as well as super
methods (for optional "annotation inheritance"). Note that none of
this is provided by the JDK's introspection facilities themselves.
As a general rule for runtime-retained annotations (e.g. for transaction
control, authorization or service exposure), always use the lookup methods on
this class (e.g.,
findAnnotation(Method, Class)
,
getAnnotation(Method, Class)
, and
getAnnotations(Method)
)
instead of the plain annotation lookup methods in the JDK. You can still
explicitly choose between lookup on the given class level only
(
getAnnotation(Method, Class)
) and lookup in the entire inheritance
hierarchy of the given method (
findAnnotation(Method, Class)
).
Author:
Rob Harrop, Juergen Hoeller, Sam Brannen, Mark Fisher
See Also:
AccessibleObject.getAnnotations()
,
Method.getAnnotation(Class)
Find a single
Annotation
of
annotationType
from the
supplied
Class
, traversing its interfaces and super classes
if no annotation can be found on the given class itself.
static
<A extends
Annotation
>
findAnnotation
(
Method
method,
Class
<A> annotationType)
Get a single
Annotation
of
annotationType
from the
supplied
Method
, traversing its super methods if no annotation
can be found on the given method itself.
static
Class
<?>
findAnnotationDeclaringClass
(
Class
<? extends
Annotation
> annotationType,
Class
<?> clazz)
Find the first
Class
in the inheritance hierarchy of the
specified
clazz
(including the specified
clazz
itself) which declares an annotation for the
specified
annotationType
, or
null
if not
found.
static
<A extends
Annotation
>
getAnnotation
(
Method
method,
Class
<A> annotationType)
Get a single
Annotation
of
annotationType
from the
supplied
Method
.
static
Map
<
String
,
Object
>
getAnnotationAttributes
(
Annotation
annotation)
Retrieve the given annotation's attributes as a Map.
static
Annotation
[]
getAnnotations
(
Method
method)
Get all
Annotations
from the supplied
Method
.
static
Object
getDefaultValue
(
Annotation
annotation)
Retrieve the
default value
of the
"value"
attribute of a single-element
Annotation, given an annotation instance.
static
Object
getDefaultValue
(
Annotation
annotation,
String
attributeName)
Retrieve the
default value
of a named Annotation attribute,
given an annotation instance.
static
Object
getDefaultValue
(
Class
<? extends
Annotation
> annotationType)
Retrieve the
default value
of the
"value"
attribute of a single-element
Annotation, given the
annotation type
.
static
Object
getDefaultValue
(
Class
<? extends
Annotation
> annotationType,
String
attributeName)
Retrieve the
default value
of a named Annotation attribute,
given the
annotation type
.
static
Object
getValue
(
Annotation
annotation)
Retrieve the
value
of the
"value"
attribute of a single-element Annotation, given an annotation instance.
static
Object
getValue
(
Annotation
annotation,
String
attributeName)
Retrieve the
value
of a named Annotation attribute, given an
annotation instance.
static boolean
isAnnotationDeclaredLocally
(
Class
<? extends
Annotation
> annotationType,
Class
<?> clazz)
Determine whether an annotation for the specified
annotationType
is declared locally on the supplied
clazz
.
static boolean
isAnnotationInherited
(
Class
<? extends
Annotation
> annotationType,
Class
<?> clazz)
Determine whether an annotation for the specified
annotationType
is present on the supplied
clazz
and is
inherited
(i.e., not declared locally for the class).
public static
Annotation
[]
getAnnotations
(
Method
method)
Get all
Annotations
from the supplied
Method
.
Correctly handles bridge
Methods
generated by the compiler.
Parameters:
method
- the method to look for annotations on
Returns:
the annotations found
See Also:
BridgeMethodResolver.findBridgedMethod(Method)
public static <A extends
Annotation
> A
getAnnotation
(
Method
method,
Class
<A> annotationType)
Get a single
Annotation
of
annotationType
from the
supplied
Method
.
Correctly handles bridge
Methods
generated by the compiler.
Parameters:
method
- the method to look for annotations on
annotationType
- the annotation class to look for
Returns:
the annotations found
See Also:
BridgeMethodResolver.findBridgedMethod(Method)
public static <A extends
Annotation
> A
findAnnotation
(
Method
method,
Class
<A> annotationType)
Get a single
Annotation
of
annotationType
from the
supplied
Method
, traversing its super methods if no annotation
can be found on the given method itself.
Annotations on methods are not inherited by default, so we need to handle
this explicitly. Tge
Parameters:
method
- the method to look for annotations on
annotationType
- the annotation class to look for
Returns:
the annotation found, or
null
if none found
public static <A extends
Annotation
> A
findAnnotation
(
Class
<?> clazz,
Class
<A> annotationType)
Find a single
Annotation
of
annotationType
from the
supplied
Class
, traversing its interfaces and super classes
if no annotation can be found on the given class itself.
This method explicitly handles class-level annotations which are
not declared as
inherited
as well as annotations on interfaces
.
The algorithm operates as follows: Searches for an annotation on the given
class and returns it if found. Else searches all interfaces that the given
class declares, returning the annotation from the first matching candidate,
if any. Else proceeds with introspection of the superclass of the given class,
checking the superclass itself; if no annotation found there, proceeds with
the interfaces that the superclass declares. Recursing up through the entire
superclass hierarchy if no match is found.
Parameters:
clazz
- the class to look for annotations on
annotationType
- the annotation class to look for
Returns:
the annotation found, or
null
if none found
findAnnotationDeclaringClass
public static
Class
<?>
findAnnotationDeclaringClass
(
Class
<? extends
Annotation
> annotationType,
Class
<?> clazz)
Find the first
Class
in the inheritance hierarchy of the
specified
clazz
(including the specified
clazz
itself) which declares an annotation for the
specified
annotationType
, or
null
if not
found. If the supplied
clazz
is
null
,
null
will be returned.
If the supplied
clazz
is an interface, only the interface
itself will be checked; the inheritance hierarchy for interfaces will not
be traversed.
The standard
Class
API does not provide a mechanism for
determining which class in an inheritance hierarchy actually declares an
Annotation
, so we need to handle this explicitly.
Parameters:
annotationType
- the Class object corresponding to the annotation type
clazz
- the Class object corresponding to the class on which to
check for the annotation, or
null
.
Returns:
the first
Class
in the inheritance hierarchy of the
specified
clazz
which declares an annotation for the specified
annotationType
, or
null
if not found.
See Also:
Class.isAnnotationPresent(Class)
,
Class.getDeclaredAnnotations()
isAnnotationDeclaredLocally
public static boolean
isAnnotationDeclaredLocally
(
Class
<? extends
Annotation
> annotationType,
Class
<?> clazz)
Determine whether an annotation for the specified
annotationType
is declared locally on the supplied
clazz
.
The supplied
Class
object may represent any type.
Note: This method does
not
determine if the annotation
is
inherited
. For greater clarity
regarding inherited annotations, consider using
isAnnotationInherited(Class, Class)
instead.
Parameters:
annotationType
- the Class object corresponding to the annotation type
clazz
- the Class object corresponding to the class on which to
check for the annotation
Returns:
true
if an annotation for the specified
annotationType
is declared locally on the supplied
clazz
See Also:
Class.getDeclaredAnnotations()
,
isAnnotationInherited(Class, Class)
isAnnotationInherited
public static boolean
isAnnotationInherited
(
Class
<? extends
Annotation
> annotationType,
Class
<?> clazz)
Determine whether an annotation for the specified
annotationType
is present on the supplied
clazz
and is
inherited
(i.e., not declared locally for the class).
If the supplied
clazz
is an interface, only the interface
itself will be checked. In accord with standard meta-annotation
semantics, the inheritance hierarchy for interfaces will not be
traversed. See the
JavaDoc
for the
@Inherited meta-annotation for further details regarding annotation
inheritance.
Parameters:
annotationType
- the Class object corresponding to the annotation type
clazz
- the Class object corresponding to the class on which to
check for the annotation
Returns:
true
if an annotation for the specified
annotationType
is present on the supplied
clazz
and is
inherited
See Also:
Class.isAnnotationPresent(Class)
,
isAnnotationDeclaredLocally(Class, Class)
getAnnotationAttributes
public static
Map
<
String
,
Object
>
getAnnotationAttributes
(
Annotation
annotation)
Retrieve the given annotation's attributes as a Map.
Parameters:
annotation
- the annotation to retrieve the attributes for
Returns:
the Map of annotation attributes, with attribute names as keys
and corresponding attribute values as values
public static
Object
getValue
(
Annotation
annotation)
Retrieve the
value
of the
"value"
attribute of a single-element Annotation, given an annotation instance.
Parameters:
annotation
- the annotation instance from which to retrieve the value
Returns:
the attribute value, or
null
if not found
See Also:
getValue(Annotation, String)
Parameters:
annotation
- the annotation instance from which to retrieve the value
attributeName
- the name of the attribute value to retrieve
Returns:
the attribute value, or
null
if not found
See Also:
getValue(Annotation)
public static
Object
getDefaultValue
(
Annotation
annotation)
Retrieve the
default value
of the
"value"
attribute of a single-element
Annotation, given an annotation instance.
Parameters:
annotation
- the annotation instance from which to retrieve
the default value
Returns:
the default value, or
null
if not found
See Also:
getDefaultValue(Annotation, String)
Parameters:
annotation
- the annotation instance from which to retrieve
the default value
attributeName
- the name of the attribute value to retrieve
Returns:
the default value of the named attribute, or
null
if not found.
See Also:
getDefaultValue(Class, String)
getDefaultValue
public static
Object
getDefaultValue
(
Class
<? extends
Annotation
> annotationType)
Retrieve the
default value
of the
"value"
attribute of a single-element
Annotation, given the
annotation type
.
Parameters:
annotationType
- the
annotation type
for which the
default value should be retrieved
Returns:
the default value, or
null
if not found
See Also:
getDefaultValue(Class, String)
getDefaultValue
public static
Object
getDefaultValue
(
Class
<? extends
Annotation
> annotationType,
String
attributeName)
Retrieve the
default value
of a named Annotation attribute,
given the
annotation type
.
Parameters:
annotationType
- the
annotation type
for which the
default value should be retrieved
attributeName
- the name of the attribute value to retrieve.
Returns:
the default value of the named attribute, or
null
if not found
See Also:
getDefaultValue(Annotation, String)
