I'm using the javax.websocket API in Java. I am using a Jetty server and Javascript for the client. How do I initiate sendMessage from the server?
Details: Am using a jetty-maven-plugin 9.4.8.v20171121.
Server-side dependencies: org.eclipse.jetty.websocket - websocket-server and javax-websocket-server-impl.
Here's my server code:
package com.trice.server.web;
import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.server.ServerEndpoint;
@ServerEndpoint("/WebSocketTestServlet")
public class WebSocketTestServlet {
@OnOpen
public void onOpen(){
System.out.println("Open Connection ...");
}
@OnClose
public void onClose(){
System.out.println("Close Connection ...");
}
@OnMessage
public String onMessage(String message){
System.out.println("Message from the client: " + message);
String echoMsg = "Echo from the server : " + message;
return echoMsg;
}
@OnError
public void onError(Throwable e){
e.printStackTrace();
}
}
And client code:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Tomcat WebSocket</title>
</head>
<body>
<form>
<input id="message" type="text">
<input onclick="wsSendMessage();" value="Echo" type="button">
<input onclick="wsCloseConnection();" value="Disconnect" type="button">
</form>
<br>
<textarea id="echoText" rows="5" cols="30"></textarea>
<script type="text/javascript">
var webSocket = new WebSocket("ws://localhost:8080/WebSocketTestServlet");
var echoText = document.getElementById("echoText");
echoText.value = "";
var message = document.getElementById("message");
webSocket.onopen = function(message){ wsOpen(message);};
webSocket.onmessage = function(message){ wsGetMessage(message);};
webSocket.onclose = function(message){ wsClose(message);};
webSocket.onerror = function(message){ wsError(message);};
function wsOpen(message){
echoText.value += "Connected ... \n";
}
function wsSendMessage(){
webSocket.send(message.value);
echoText.value += "Message sent to the server : " + message.value + "\n";
message.value = "";
}
function wsCloseConnection(){
webSocket.close();
}
function wsGetMessage(message){
echoText.value += "Message received from to the server : " + message.data + "\n";
}
function wsClose(message){
echoText.value += "Disconnect ... \n";
console.log("disconnect", message);
}
function wsError(message){
echoText.value += "Error \n";
console.log("error", message);
}
</script>
</body>
</html>
Reference link
Appreciate any help. Thanks.
asked Jan 4, 2018 at 10:49
raksheetbhat
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1 Answer 1
There was a very easy answer to my question. All I needed to do was:
session.getBasicRemote().sendText("Some string");
answered Jan 8, 2018 at 6:08
raksheetbhat
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4 Comments
Ganapathi Basimsetti
How do you get the session object?? @raksheetbhat
raksheetbhat
Define a websocket ServerEndpoint which defines callback methods -
@OnOpen public void onOpen(Session wsSession, @PathParam("param") final String param) which gives you a websocket.session object.Ganapathi Basimsetti
I had looked at the article previously. In that sending of a message to user 2 is initiated by receiving of a message from user 2. So it's not purely initiated from server side. In my case, it's like after completion of asynchronous batch job, i need to send a message to the browser. In this case how can we get the session?
raksheetbhat
You can maintain a list of user sessions server side, and retrieve those sessions when you need to send a message to all active users. Or maintain a hashmap with userid, so you can retrieve sessions for particular users.
default
session.getBasicRemote().sendText("yahooo!");@Observes) in yourServerEndpoint, please be aware that if no websocket client is connected, you may encounter some issues. In my project, we use a session handler class to handle CDI events