I am trying implement websockets using spring with a java/web application to allow it to exchangte messages with a application written with c++ using qt (and the websockets library from it).
I have in my java/spring application this configuration:
WebScoketConfig.java
@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
registry.addHandler(new SocketHandler(), "/name");
}
}
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);
}
}
and I created a very simple qt-creator project, with a main function and one class MainWindow, with two objects: a lineEdit, where the user types a message to send to server, and a pushButton, to proceed with the data send.
In my MainWindow class, I implement this slot to handle the data exchange:
void MainWindow::on_pushButton_clicked()
{
QString message = this->ui->lineEdit->text();
QWebSocket m_webSocket;
m_webSocket.open(QUrl(QStringLiteral("ws://localhost:8080/name")));
m_webSocket.sendTextMessage("Hello " + message + " !");
m_webSocket.close();
}
But when I execute both applications, and try send a message for the java/web application, nothing happens. I pretty sure the mistake I made it's on the c++/qt side, since in the java/spring side I have a html/javascript code which allow me testing the message exchage, nd works fine.
Anyone can tell me what I am doing wrong here?
update: minimal reproducible example - java/spring
the project can be generated with start.spring.io, only with spring-websocket as dependency. besides the 2 files I already add above, the project will have:
resources/static/index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Hello WebSocket</title>
<link href="/main.css" rel="stylesheet">
</head>
<body>
<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 src="/app.js"></script>
</body>
</html>
resources/app.js
var ws;
function connect() {
ws = new WebSocket('ws://localhost:8080/name');
ws.onmessage = function(text) {
var tr = document.createElement("tr");
var td = document.createElement("td");
td.innerText = text.data;
tr.appendChild(td);
document.querySelector("#greetings").appendChild(tr);
}
document.querySelector("#connect").setAttribute("disabled", "disabled");
document.querySelector("#disconnect").removeAttribute("disabled");
document.querySelector("#conversation").style.display = 'block';
document.querySelector("#greetings").innerHTML = "";
}
function disconnect() {
if (ws != null)
ws.close();
document.querySelector("#connect").removeAttribute("disabled");
document.querySelector("#disconnect").setAttribute("disabled", "disabled");
document.querySelector("#conversation").style.display = 'none';
document.querySelector("#greetings").innerHTML = "";
}
function send() {
var name = document.querySelector("#name");
var data = JSON.stringify({'name': name.value});
ws.send(data);
}
after build with mvn package, just run with java -jar target/app.jar.
update: minimal reproducible example - c++/qt
project is created with qt-creator, as type qt-widget. It will create a project with 5 files: websocket.pro, mainwindow.ui, mainwindow.h, mainwindow.cpp and main.cpp.
Open mainwindow.ui and add a lineEdit and pushButton from toolbar. right-click on the pushButton and choose Go to slot and select clicked(). Add the code above.
Update 2
void MainWindow::on_pushButton_clicked()
{
QString message = ui->lineEdit->text();
connect(&m_webSocket, &QWebSocket::connected, [this, message](){
QJsonObject object
{
{"name", message}
};
QJsonDocument d(object);
m_webSocket.sendTextMessage(d.toJson().toStdString().c_str());
m_webSocket.close();
});
m_webSocket.open(QUrl(QStringLiteral("ws://localhost:8080/name")));
}