communication between java server and javascript

Question

I have multithreaded chatting java server which can handle number of clients (java). They can simultaneous talk with each other. They are connected through network socket. Besides their own conversation words, my purpose is to display the conversation words they do in web browser through web application. I am thinking about JavaScript but couldn't figure out how to implement javascript for web application because I will need object or data to pass to javascript side from server( java) side.

Following is the multithreaded server and this works fine with multiple clients.

        public class GoodChatServer {
         ………
public static void main(String[] args) throws Exception {
    System.out.println("The chat server is running.");
    ServerSocket listener = new ServerSocket(PORT);
    try {
        ….
        }
    } finally {
    …..
    }
}
private static class Handler extends Thread {


   ……….
        this.socket = socket;
    }

   public void run() {
        try {

            in = new BufferedReader(new InputStreamReader(
                socket.getInputStream()));
            out = new PrintWriter(socket.getOutputStream(), true);
            while (true) {
                out.println("SUBMITNAME");
                name = in.readLine();
                if (name == null) {
               ..
                }

                synchronized (names) {
                    if (!names.contains(name)) {
                        names.add(name);
                        break;
                    }

you can create a GUI using javascript to do so and show that converstation there. — Divya
– Divya, Commented Mar 27, 2014 at 12:42
thanks A5I-IE5 !! But the thing is I have protbuf data in my java server and I want to pass that to javascript ....means how do I access class or object of my server ( java) from javascript....and also pass protobuf. — Samaya
– Samaya, Commented Mar 27, 2014 at 14:38
@ A5I-IE5, Technically yes. I want to call java from JavaScript to get protobuf data in javascript(can be other language also) side for displaying .. I looked for AJAX but they support either xml or JSON data which is not in my case.. — Samaya
– Samaya, Commented Mar 27, 2014 at 22:22

drnugent · Accepted Answer · 2014-03-27 14:39:41Z

1

There are a plethora of ways to display chat information from a Java server in a browser using JavaScript. Since you are already using sockets for your Java clients, one option would be to use WebSockets. Oracle provides an introduction to Java Websockets here, which should help you with the server side of things. Mozilla also has a tutorial for writing browser-based websockets here.

Another option you may consider is to relay your data across global real-time network, such as PubNub. PubNub provides a Java API and JavaScript API which will allow you to publish messages from your Java server to your JavaScript clients, using code such as:

<script src="http://cdn.pubnub.com/pubnub.min.js"></script>
<script>(function(){

var pubnub = PUBNUB.init({
    publish_key   : 'demo',
    subscribe_key : 'demo'
})

pubnub.subscribe({
    channel : "my_chat_channel",
    message : function(m){ alert(m) }, //Display the chat message
})});</script>

On the Java server, you'd write your publish code:

Pubnub pubnub = new Pubnub("demo", "demo");

Callback callback = new Callback() {
    public void successCallback(String channel, Object response) {
        System.out.println(response.toString());
    }
    public void errorCallback(String channel, PubnubError error) {
        System.out.println(error.toString());
    }
};
pubnub.publish("my_chat_channel", "Here is my amazing chat message!" , callback);

PubNub is currently free for up to 1 million messages per month. Good luck!

answered Mar 27, 2014 at 14:39

drnugent

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2 Comments

Samaya Over a year ago

@ drnugent, Thanks for advice...I will definetly look for PubNub..but I have one more doubt, will it support to transfer PROTBUF data ?

drnugent Over a year ago

You should be able to serialize and deserialize any data, however you might consider using JSON since your messages will be read by a JavaScript client.

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