import java.io.IOException;
 
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
 
/** 
 * @ServerEndpoint gives the relative name for the end point
 * This will be accessed via ws://localhost:8080/EchoChamber/echo
 * Where "localhost" is the address of the host,
 * "EchoChamber" is the name of the package
 * and "echo" is the address to access this class from the server
 */
@ServerEndpoint("/echo") 
public class EchoServer {
    /**
     * @OnOpen allows us to intercept the creation of a new session.
     * The session class allows us to send data to the user.
     * In the method onOpen, we'll let the user know that the handshake was 
     * successful.
     */
    @OnOpen
    public void onOpen(Session session){
        System.out.println(session.getId() + " has opened a connection"); 
        try {
            session.getBasicRemote().sendText("Connection Established");
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
 
    /**
     * When a user sends a message to the server, this method will intercept the message
     * and allow us to react to it. For now the message is read as a String.
     */
    @OnMessage
    public void onMessage(String message, Session session){
        System.out.println("Message from " + session.getId() + ": " + message);
        try {
            session.getBasicRemote().sendText(message);
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
 
    /**
     * The user closes the connection.
     * 
     * Note: you can't send messages to the client from this method
     */
    @OnClose
    public void onClose(Session session){
        System.out.println("Session " +session.getId()+" has ended");
    }
}

import javax.websocket.Endpoint;
import javax.websocket.EndpointConfig;
import javax.websocket.MessageHandler;
import javax.websocket.Session;
import javax.websocket.CloseReason;

public class TestEndPoint extends Endpoint {

    @Override
    public void onOpen(Session session, EndpointConfig EndpointConfig) {
        session.addMessageHandler(new MessageHandler.Whole<String>() {
            @Override
            public void onMessage(String message) {
                System.out.println("Received message: "+message);
            }
        });
    }

    @Override
    public void onClose(Session session, CloseReason closeReason) {
        super.onClose(session, closeReason);
    }

    @Override
    public void onError(Session session, Throwable thr) {
        super.onError(session, thr);
    }
}

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;
import javax.websocket.DeploymentException;
import javax.websocket.OnMessage;
import javax.websocket.server.ServerContainer;
import javax.websocket.server.ServerEndpoint;

@WebListener
@ServerEndpoint("/annotated")
public class MyServletContextListenerAnnotated implements ServletContextListener {

    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        final ServerContainer serverContainer = (ServerContainer) servletContextEvent.getServletContext()
                                                    .getAttribute("javax.websocket.server.ServerContainer");

        try {
            serverContainer.addEndpoint(MyServletContextListenerAnnotated.class);
        } catch (DeploymentException e) {
            e.printStackTrace();
        }
    }

    @OnMessage
    public String onMessage(String message) {
        return message;
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {
    }
}