public interface Authentication

 SecurityContextHolder.getContext().setAuthentication(anAuthentication);
 Note that unless the Authentication has the authenticated property set to true, it will
 still be authenticated by any security interceptor (for method or web invocations) which encounters it.
 In most cases, the framework transparently takes care of managing the security context and authentication objects
 for you.
Collection<GrantedAuthority> getAuthorities()
Set by an AuthenticationManager to indicate the authorities that the principal has been
 granted. Note that classes should not rely on this value as being valid unless it has been set by a trusted
 AuthenticationManager.
 Implementations should ensure that modifications to the returned collection
 array do not affect the state of the Authentication object, or use an unmodifiable instance.
Returns:
the authorities granted to the principal, or an empty collection if the token has not been authenticated.
 Never null.
Object getCredentials()
The credentials that prove the principal is correct. This is usually a password, but could be anything
 relevant to the AuthenticationManager. Callers are expected to populate the credentials.
Object getDetails()
Stores additional details about the authentication request. These might be an IP address, certificate
 serial number etc.
Object getPrincipal()
The identity of the principal being authenticated. In the case of an authentication request with username and
 password, this would be the username. Callers are expected to populate the principal for an authentication
 request.
 The AuthenticationManager implementation will often return an Authentication containing
 richer information as the principal for use by the application. Many of the authentication providers will
 create a UserDetails object as the principal.
boolean isAuthenticated()
Used to indicate to AbstractSecurityInterceptor whether it should present the
 authentication token to the AuthenticationManager. Typically an AuthenticationManager
 (or, more often, one of its AuthenticationProviders) will return an immutable authentication token
 after successful authentication, in which case that token can safely return true to this method.
 Returning true will improve performance, as calling the AuthenticationManager for
 every request will no longer be necessary.
 For security reasons, implementations of this interface should be very careful about returning
 true from this method unless they are either immutable, or have some way of ensuring the properties
 have not been changed since original creation.
Returns:
true if the token has been authenticated and the AbstractSecurityInterceptor does not need
         to present the token to the AuthenticationManager again for re-authentication.
setAuthenticated
void setAuthenticated(boolean isAuthenticated)
                      throws IllegalArgumentException
See isAuthenticated() for a full description.
 Implementations should always allow this method to be called with a false parameter,
 as this is used by various classes to specify the authentication token should not be trusted.
 If an implementation wishes to reject an invocation with a true parameter (which would indicate
 the authentication token is trusted - a potential security risk) the implementation should throw an
 IllegalArgumentException.
Parameters:
isAuthenticated - true if the token should be trusted (which may result in an exception) or
        false if the token should not be trusted
Throws:
IllegalArgumentException - if an attempt to make the authentication token trusted (by passing
         true as the argument) is rejected due to the implementation being immutable or
         implementing its own alternative approach to isAuthenticated()