Java WebSocket Libraries: Complete Guide to Real-Time Implementation

Java WebSocket Libraries: Complete Guide to Developing Real-Time Applications

WebSocket is a protocol that enables two-way communication between a client and a server over a single long-lived TCP connection. In Java, there are several mature libraries that simplify working with WebSocket. In this article, we will review the main libraries, their capabilities, and provide practical code examples.

1. Java WebSocket API (JSR 356)

The standard API for working with WebSocket in Java EE / Jakarta EE. It is part of application servers (WildFly, TomEE, GlassFish) and allows creating both server and client endpoints.

Key features:

• Annotations @ServerEndpoint and @ClientEndpoint
• Support for text and binary messages
• Session and lifecycle management
• Integration with CDI (Contexts and Dependency Injection)

Server endpoint example:

import javax.websocket.*;import javax.websocket.server.ServerEndpoint;import java.io.IOException;

@ServerEndpoint("/chat")public class ChatEndpoint {

    @OnOpen    public void onOpen(Session session) {        System.out.println("New connection: " + session.getId());        session.getUserProperties().put("username", "Guest");    }

    @OnMessage    public String onMessage(String message, Session session) {        String username = (String) session.getUserProperties().get("username");        return username + ": " + message;    }

    @OnClose    public void onClose(Session session, CloseReason reason) {        System.out.println("Connection closed: " + reason.getReasonPhrase());    }

    @OnError    public void onError(Session session, Throwable error) {        error.printStackTrace();    }}

Client example:

import javax.websocket.*;import java.net.URI;

@ClientEndpointpublic class ChatClient {

    private Session session;

    @OnOpen    public void onOpen(Session session) {        System.out.println("Connected to server");        this.session = session;    }

    @OnMessage    public void onMessage(String message) {        System.out.println("Received: " + message);    }

    public void sendMessage(String message) throws IOException {        if (session != null && session.isOpen()) {            session.getBasicRemote().sendText(message);        }    }

    public static void main(String[] args) throws Exception {        WebSocketContainer container = ContainerProvider.getWebSocketContainer();        ChatClient client = new ChatClient();        container.connectToServer(client, new URI("ws://localhost:8080/chat"));        client.sendMessage("Hello, world!");        Thread.sleep(1000);    }}

2. Tyrus (Reference Implementation)

Tyrus is the reference implementation of JSR 356 from Oracle. It can be used as a standalone library without a full application server. Ideal for microservices and lightweight applications.

Features:

• Works with Grizzly, Jetty, or JDK HTTP server
• Support for SockJS for compatibility with browsers without WebSocket
• Configurable filters and interceptors
• Flexible configuration via XML or Java Config

Standalone server example on Tyrus + Grizzly:

import org.glassfish.tyrus.server.Server;import javax.websocket.*;import javax.websocket.server.ServerEndpoint;

@ServerEndpoint("/echo")public class EchoEndpoint {

    @OnMessage    public String echo(String message) {        return "Echo: " + message;    }

    public static void main(String[] args) {        Server server = new Server("localhost", 8025, "/ws", EchoEndpoint.class);        try {