18.4 Annotated Endpoints

The following example shows how to create the same endpoint from Programmatic Endpoints using annotations instead:

@ServerEndpoint("/echo")
public class EchoEndpoint {
   @OnMessage
   public void onMessage(Session session, String msg) {
      try {
         session.getBasicRemote().sendText(msg);
      } catch (IOException e) { ... }
   }
}

The annotated endpoint is simpler than the equivalent programmatic endpoint, and it is deployed automatically with the application to the relative path defined in the ServerEndpoint annotation. Instead of having to create an additional class for the message handler, this example uses the OnMessage annotation to designate the method invoked to handle messages.

Table 18-1 lists the annotations available in the javax.websocket package to designate the methods that handle lifecycle events. The examples in the table show the most common parameters for these methods. See the API reference for details on what combinations of parameters are allowed in each case.

@OnOpen
public void open(Session session, 
                 EndpointConfig conf) { }

@OnMessage
public void message(Session session, 
                    String msg) { }

@OnError
public void error(Session session, 
                  Throwable error) { }

@OnClose
public void close(Session session, 
                  CloseReason reason) { }