How to read the json request from Websocket subscriber(client) at Javax.websocket?

Question

The below is my Websocket subscription code.

Client side:

var request = '{"sessionId": "_fjuhdf896786767", "username":"admin", "status":true}'
ws = new WebSocket(wsUri);
console.log("registered");
    ws.onopen = function() {
        console.log("connection opened!")
        ws.send(request);
    }

    ws.onmessage = function(msg) {
        console.log("received message:");
        window.getData(JSON.parse(msg.data));
    }

At server side, the implementioation of websocket is below:

@ServerEndPoint(value="/status")
public class WebsocketServer {

    @OnOpen
    public void OpenMsg(Session session, EndpointConfig cnfg) {

        String retdata = "";
        try {
            if (session.isOpen()) {
                log.info("OpenMsg() payload req data from client"  + decoder);
                retdata = getCount(decoder);
                log.info("OpenMsg() retdata " + retdata);
                session.getBasicRemote().sendText(retdata.toString());
                try {
                  Thread.sleep(pollinterval);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        } catch (IOException e) {
            try {
                session.close();
                log.error("Exception occured while Opening WS Session");
                e.printStackTrace();
            } catch (IOException e1) {
                // Ignore
            }
        }

    }                   
}

I would like to know how to read the json request string from "ws.send(request);" at the server side(javax.websocket). I saw Encoder and Decoder, but in this case i am only sending the json request as a string which is not encoded as shown above. Could any body tell me, how to read json string as a payload in Javax.websocket.

Answer 1

I guess that a simple JSON reader will do the trick:

@OnMessage
public void onMessage(Session session, String message) {
    JsonObject json = Json.createReader(new StringReader(message)).readObject();
    System.out.println("Received json: " + json);
    // or do something more JSON-like:
    // String myField = json.getString("key");
}

Encoder and decoder are not directly linked to payload but rather if you wish to directly manipulate object. If you're using decoders, your onMessage method can look like

@OnMessage
public void onMessage(Session session, MyMessageClass message){
    String myInput = message.getInput();
    String otherUsefulInformation = message.getInformation();
}

and when you're using encoder, it's about sending object instead of plain text:

@OnMessage
public void onMessage(Session session, MyMessageClass message){
    // process input

    MyAnswerClass answer = new MyAnswerClass(...);
    session.getBasicRemote().sendObject(answer);

    // without encoder, you are bound to use 
    // session.getBasicRemote().sendText(...)
    // or
    // session.getBasicRemote().sendBinary(...)
}

Answer 2

you can use annotation "ClientEndPoint" on your client side :

@ClientEndpoint(encoders = MessageEncoder.class, decoders = MessageDecoder.class)

use : Session.getBasicRemote().sendObject(message);

class MessageEncoder implements Encoder.Text<Message>
class MessageDecoder implements Decoder.Text<Message>

Answer 3

Oracle Using WebSocket Protocal in WebLogic Server

Oracle OnMessage Interface

Be sure to implement the OnMessage Interface

@OnMessage public void handleMessage(String message, Session session) { // message will contain the body content you sent }