Interceptors

Interceptors are an important concept of the xdi2-messaging and xdi2-server-logic components. They are used as an extensibility mechanism.

Interfaces and Classes

• xdi2.messaging.target.interceptor.MessagingTargetInterceptor: Interceptor that is executed when a messaging target is initialized and shut down.
• xdi2.messaging.target.interceptor.MessageEnvelopeInterceptor: Interceptor that is executed before and after a message envelope is executed, as well as when an exception occurs while executing the message envelope.
• xdi2.messaging.target.interceptor.MessageInterceptor: Interceptor that is executed before and after a message is executed.
• xdi2.messaging.target.interceptor.OperationInterceptor: Interceptor that is executed before and after an operation is executed.
• xdi2.messaging.target.interceptor.TargetInterceptor: Interceptor that is executed when an operation is executed on an XDI statement or an XDI address.
• xdi2.messaging.target.interceptor.ResultInterceptor: Interceptor that is executed on a message result after a message envelope has been executed.
• xdi2.server.interceptor.EndpointServletInterceptor: Interceptor that is executed when the EndpointServlet is initialized, destroyed, or when it receives an incoming HTTP request.

Implementation and Use of Interceptors

The interceptors of the xdi2-messaging component are attached to messaging targets. The EndpointServletInterceptor of the xdi2-server-logic component are attached to the EndpointServlet.

A single class can implement multiple interceptor interfaces. For example, an interceptor might need to be called before each message is executed, and when an operation is executed on an XDI statement or an XDI address. Therefore, this interceptor would implement the MessageInterceptor and the TargetInterceptor interfaces.