access websocket from a desktop application - spring

Question

I have a project with spring-websocket with this setup:
SocketHandler.java
#Component
public class SocketHandler extends TextWebSocketHandler {
List<WebSocketSession> sessions = new CopyOnWriteArrayList<>();
#Override
public void handleTextMessage(WebSocketSession session, TextMessage message) throws InterruptedException, IOException {
Map<String, String> value = new Gson().fromJson(message.getPayload(), Map.class);
session.sendMessage(new TextMessage("Hello " + value.get("name") + " !"));
}
#Override
public void afterConnectionEstablished(WebSocketSession session) throws Exception {
sessions.add(session);
}
}
WebSocketConfig.java
#Configuration
#EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
registry.addHandler(new SocketHandler(), "/name");
}
}
index.html
<table>
<tr>
<td>
<button id="connect" type="button" onclick="connect();">Connect</button>
<button id="disconnect" type="button" disabled="disabled" onclick="disconnect();">Disconnect</button>
</td>
<td>
<label for="name">What is your name?</label>
<input type="text" id="name" placeholder="Your name here...">
<button id="send" type="button" onclick="send();">Send</button>
</td>
</tr>
</table>
<hr>
<table id="conversation" border="2">
<thead>
<tr>
<th>Greetings</th>
</tr>
</thead>
<tbody id="greetings">
</tbody>
</table>
script.js
var ws;
function setConnected(connected) {
var connect = document.querySelector("#connect");
var disconnect = document.querySelector("#disconnect");
var conversation = document.querySelector("#conversation");
var greetings = document.querySelector("#greetings");
if(connected) {
connect.setAttribute("disabled", "disabled");
disconnect.removeAttribute("disabled");
conversation.style.display = 'block';
} else {
connect.removeAttribute("disabled");
disconnect.setAttribute("disabled", "disabled");
conversation.style.display = 'none';
}
greetings.innerHTML = "";
}
function connect() {
ws = new WebSocket('ws://localhost:8080/name');
ws.onmessage = function(text) {
showGreeting(text.data);
}
setConnected(true);
}
function disconnect() {
if (ws != null) {
ws.close();
}
setConnected(false);
}
function send() {
var name = document.querySelector("#name");
var data = JSON.stringify({'name': name.value});
ws.send(data);
}
function showGreeting(message) {
var greeting = document.querySelector("#greetings");
var tr = document.createElement("tr");
var td = document.createElement("td");
td.innerText = message;
tr.appendChild(td);
greeting.appendChild(tr);
}
I wonder if it's possible develop a desktop client application, for example, with Java/Swing or C++/Qt, which could communicate with this application as if it was a server, receiving the data from the desktop application and broadcast to all clients connected to it.

Answer 1

Here's a minimal, non-GUI version of Java based WebSocket client.
Server
SocketHandler.java
import com.google.gson.Gson;
import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.concurrent.CopyOnWriteArrayList;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.handler.TextWebSocketHandler;
#Component
public class SocketHandler extends TextWebSocketHandler {
List<WebSocketSession> sessions = new CopyOnWriteArrayList<>();
#Override
public void handleTextMessage(WebSocketSession currentSession, TextMessage message) throws InterruptedException, IOException {
Map<String, String> value = new Gson().fromJson(message.getPayload(), Map.class);
TextMessage textMessage = new TextMessage("Hello from " + value.get("name") + "!");
for (WebSocketSession session : sessions) {
if (session.isOpen()) {
session.sendMessage(textMessage);
}
}
}
#Override
public void afterConnectionEstablished(WebSocketSession session) throws Exception {
sessions.add(session);
}
}
Client
MyWebSocketClient.java
package com.example;
import java.net.URI;
import java.util.Scanner;
import javax.websocket.*;
import javax.websocket.RemoteEndpoint.Basic;
#ClientEndpoint
public class MyWebSocketClient {
#OnMessage
public void onMessage(String message) {
System.out.println("[Greetings] " + message + "\n");
}
public static void main(String[] args) {
WebSocketContainer container = null;
Session session = null;
Basic basicRemote = null;
Scanner inputScanner = null;
try {
container = ContainerProvider.getWebSocketContainer();
session = container.connectToServer(MyWebSocketClient.class, URI.create("ws://localhost:8080/name"));
basicRemote = session.getBasicRemote();
inputScanner = new Scanner(System.in);
while (true) {
String input = inputScanner.nextLine();
basicRemote.sendText("{ \"name\": \"" + input + "\" }");
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
pom.xml
<dependencies>
<dependency>
<groupId>javax.websocket</groupId>
<artifactId>javax.websocket-client-api</artifactId>
<version>1.1</version>
</dependency>
<dependency>
<groupId>org.glassfish.tyrus.bundles</groupId>
<artifactId>tyrus-standalone-client</artifactId>
<version>1.15</version>
</dependency>
</dependencies>
Result: