Implement WebSocket in a Java Servlet

#websocket

#tomcat

#java

#servlet

#j2ee

Preface:

This is a simple way to implement the WebSocket in a servlet Java with Tomcat server.

Requirements:

Tomcat 7.x
Java J2EE (i use version 7...)
File exemple: WSTest/ws.java

Code:

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import org.apache.catalina.websocket.MessageInbound;
import org.apache.catalina.websocket.StreamInbound;
import org.apache.catalina.websocket.WebSocketServlet;
import org.apache.catalina.websocket.WsOutbound;

/*
 * @WebServlet indicates the url of this file (ex: localhost:8080/WSTest/ws)
*/
@WebServlet("/ws")
public class ws extends WebSocketServlet{
 private static final long serialVersionUID = 1L;

@Override
public StreamInbound createWebSocketInbound(String arg0, HttpServletRequest arg1) {

 /*
 * arg1.getRemoteAddr() return the ip address (v4 or v6) of the client
 */
 return new WebSocket(arg1.getRemoteAddr());
}

 /*
 * The WebSocket class!!! :D
 * protected* is for testing with JUnit
 */
 protected class WebSocket extends MessageInbound{

 /*
 * Client stream reference.
 */
 private WsOutbound outbound;
 /*
 * Client IP reference.
 */
 private String ip;

 /*
 * Costructor
 * @param ipAddress
 * Client ip (v4 or v6).
 */
 protected WebSocket(String ipAddress){
 ip = ipAddress;
 }

 /*
 * Message sender.
 * @param m
 * message to client.
 */
 private void sendMessage(String m){
 try{
 outbound.writeTextMessage(CharBuffer.wrap((m).toCharArray()));
 }
 catch(IOException ioException){
 System.out.println("error opening websocket");
 }
 }

 /*
 * Client open channel.
 * @param o
 * Client stream reference.
 */
 @Override
 public void onOpen(WsOutbound o){
 this.outbound = o;
 System.out.println("socket opened!");
 }

 /**
 * Client send a char stream to server.
 * @param buffer
 * Message buffer.
 */
 @Override
 public void onTextMessage(CharBuffer buffer) throws IOException{
 /**
 * What do you do when client send a message to server.
 */
 }

 /**
 * Client send a byte stream to server.
 * @param buffer
 * Byte buffer.
 */
 @Override
 public void onBinaryMessage(ByteBuffer buffer) throws IOException {
 /**
 * What do you do when client send a byte stream to server.
 */
 }

 } //WebSocket
}//ws