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Java Platform, Enterprise Edition (Java EE) 8
The Java EE Tutorial

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 19-1 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.

Table 19-1 WebSocket Endpoint Lifecycle Annotations

Annotation	Event	Example
`OnOpen`	Connection opened	`@OnOpen public void open(Session session, EndpointConfig conf) { }`
`OnMessage`	Message received	`@OnMessage public void message(Session session, String msg) { }`
`OnError`	Connection error	`@OnError public void error(Session session, Throwable error) { }`
`OnClose`	Connection closed	`@OnClose public void close(Session session, CloseReason reason) { }`

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