[Pattern] WebSocket clients with java.net.http

[brunoborges]

Category

io

Slug

http-websocket-client

Title

WebSocket clients with java.net.http

Difficulty

intermediate

Since JDK

11

Summary

Use the standard asynchronous WebSocket client instead of custom protocol handling or third-party clients.

Old code label

Third-party WebSocket client

Old code

WebSocketClient client = new WebSocketClient(serverUri) {
    @Override
    public void onMessage(String message) {
        handle(message);
    }
};
client.connect();

Modern code label

Java 11+

Modern code

HttpClient.newHttpClient()
        .newWebSocketBuilder()
        .buildAsync(serverUri, new WebSocket.Listener() {
            @Override
            public CompletionStage<?> onText(
                    WebSocket socket, CharSequence data, boolean last) {
                handle(data.toString());
                return WebSocket.Listener.super.onText(socket, data, last);
            }
        });

Explanation

The java.net.http package includes an asynchronous WebSocket client integrated with the standard HTTP client and CompletionStage-based flow.

Why the modern way wins

📦 No extra dependency — The client ships with the JDK.
🧵 Asynchronous API — Connection and message handling compose with CompletionStage.
🔗 Shared HTTP stack — Proxy, TLS, and client configuration use standard JDK facilities.