Below is the code for socket.
package com.shankar.rest;
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/com.shankar.rest/echo
* Where "localhost" is the address of the host,
* "com.shankar.rest" 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");
}
}
Am not sure why it throwing error when connect with JavaScript.
<!DOCTYPE html>
<html>
<head>
<title>Echo Chamber</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width">
</head>
<body>
<div>
<input type="text" id="messageinput" />
</div>
<div>
<button type="button" onclick="openSocket();">Open</button>
<button type="button" onclick="send();">Send</button>
<button type="button" onclick="closeSocket();">Close</button>
</div>
<!-- Server responses get written here -->
<div id="messages"></div>
<!-- Script to utilise the WebSocket -->
<script type="text/javascript">
var webSocket;
var messages = document.getElementById("messages");
function openSocket(){
// Ensures only one connection is open at a time
if(webSocket !== undefined && webSocket.readyState !== WebSocket.CLOSED){
writeResponse("WebSocket is already opened.");
return;
}
// Create a new instance of the websocket
webSocket = new WebSocket("ws://localhost:8080/com.shankar.rest/echo");
/**
* Binds functions to the listeners for the websocket.
*/
webSocket.onopen = function(event){
// For reasons I can't determine, onopen gets called twice
// and the first time event.data is undefined.
// Leave a comment if you know the answer.
if(event.data === undefined)
return;
writeResponse(event.data);
};
webSocket.onmessage = function(event){
writeResponse(event.data);
};
webSocket.onclose = function(event){
writeResponse("Connection closed");
};
}
/**
* Sends the value of the text input to the server
*/
function send(){
var text = document.getElementById("messageinput").value;
webSocket.send(text);
}
function closeSocket(){
webSocket.close();
}
function writeResponse(text){
messages.innerHTML += "<br/>" + text;
}
</script>
</body>
</html>
When I try to open connection from JavaScript, it throws the following error:
WebSocket connection to 'ws://localhost:8080/com.shankar.rest/echo' failed: Error during WebSocket handshake: Unexpected response code: 404
Here is my web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>Demo</display-name>
<welcome-file-list>
<welcome-file>NewFile.html</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>SimulationAPI</servlet-name>
<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>com.shankar.rest</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>SimulationAPI</servlet-name>
<url-pattern>/rest/*</url-pattern>
</servlet-mapping>
</web-app>
