Extensibility Using SIP Meta-Annotations

Meta-annotations provide built-in extensibility. SIP meta-annotations allow application developers to define and use their own annotations. For example, an application can define an annotation called foo.example.18xResponses for handling only 18x responses. A single annotation can also contain more than one SIP meta-annotation.

Example 3-6 shows a user defined annotation.

Example 3-6 User Defined Annotation

@Retention(RUNTIME)
@Target({METHOD})
@SipResponseRange(begin = 200, end = 299)
@SipMethod("INVITE")
public @interface MySucessfulInviteResponse {
}

Example 3-7 shows an annotation that combines a @SipPredicate annotation with other meta annotations

Example 3-7 Combined Annotations

@Retention(RUNTIME)
@Target({METHOD})
@SipPredicate(MyInitialInvite.Predicate.class)
@SipMethod("INVITE")
public @interface MyInitialInvite {
  class Predicate implements
  javax.servlet.sip.Predicate<SipServletRequest> {
    @Override
    public boolean apply(final SipServletRequest request) {
      return request.isInitial();
    }
  }
}

The application can then use the @MyInitialInvite annotation to select a method for handling an initial invite as shown in Example 3-8.

Example 3-8 Using a Custom Annotation

@MyInitialInvite
public void handleInviteRequest(SipServletRequest request) {
  //...
}