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WebSockets & Real-Time Systems with Spring · Lesson

WebSocket Endpoint Configuration

Configure WebSocket endpoints in Spring, defining paths and handling initial connections.

WebSocket Endpoint Configuration is a free WebSockets & Real-Time Systems with Spring lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the WebSockets & Real-Time Systems with Spring learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

What are WebSocket Endpoints?

Imagine a special doorway for real-time communication. In Spring, this doorway is called a WebSocket endpoint.

It's a specific URL path, like /ws or /chat, that your clients (e.g., web browsers) connect to for WebSocket communication. Without it, your server wouldn't know where to listen for real-time requests!

Spring Boot App Entry Point

Before configuring WebSockets, let's recall our Spring Boot application's main entry point. This is where your application starts running.

The @SpringBootApplication annotation simplifies setup by bundling common Spring annotations.

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class MyApplication {
  public static void main(String[] args) {
    SpringApplication.run(MyApplication.class, args);
  }
}

Enabling WebSocket Support

To tell Spring Boot that you want to use WebSockets, you need to enable it. This is done with a simple annotation on a configuration class.

  • Add @Configuration to mark the class as a Spring configuration.
  • Use @EnableWebSocket to activate Spring's WebSocket module.

This sets the stage for defining your endpoints.

The WebSocketConfigurer Interface

To customize how WebSockets are handled, Spring provides the WebSocketConfigurer interface. You'll implement this interface in your configuration class.

It gives you a method to override where you can register your specific WebSocket handlers and their paths.

Registering Your First Endpoint

Inside your WebSocketConfigurer implementation, you'll override the registerWebSocketHandlers method. This method takes a WebSocketHandlerRegistry object.

The registry is used to add your WebSocketHandler instances and map them to specific URL paths.

Defining the Endpoint Path

The core of endpoint configuration is the addHandler() method. It takes two main arguments:

  • Your WebSocketHandler instance (what handles messages).
  • The URL path where clients will connect (e.g., /mywebsocket).

Example: registry.addHandler(myHandler(), "/mywebsocket");

CORS and SockJS Fallback

You might need to allow connections from different domains (CORS) or support older browsers. The addHandler() method offers fluent options:

  • .setAllowedOrigins("*"): Allows connections from any domain. For production, specify exact domains.
  • .withSockJS(): Enables SockJS fallback, providing an alternative transport for browsers that don't fully support WebSockets.

Example: WebSocketConfig Class

Here's how your full configuration class might look. Notice how we implement WebSocketConfigurer and register a handler for the /ws path.

The myHandler() method creates an instance of our custom handler (defined next).

import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;
import org.springframework.context.annotation.Bean;

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {

  @Override
  public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
    registry.addHandler(myHandler(), "/ws")
            .setAllowedOrigins("*");
  }

  @Bean
  public MyWebSocketHandler myHandler() {
    return new MyWebSocketHandler();
  }
}

Example: Basic WebSocket Handler

This is a very simple MyWebSocketHandler. It extends TextWebSocketHandler and just logs when a connection is established or closed. We'll dive deeper into handling messages in the next lesson!

import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.handler.TextWebSocketHandler;

public class MyWebSocketHandler extends TextWebSocketHandler {

  @Override
  public void afterConnectionEstablished(WebSocketSession session) throws Exception {
    System.out.println("Connection established: " + session.getId());
  }

  @Override
  public void afterConnectionClosed(WebSocketSession session, 
                                    org.springframework.web.socket.CloseStatus status) 
                                    throws Exception {
    System.out.println("Connection closed: " + session.getId() + " - " + status.getReason());
  }

  // Message handling will go here in a later lesson
  @Override
  protected void handleTextMessage(WebSocketSession session, TextMessage message) {
    // For now, we just acknowledge. Message processing is next lesson.
    System.out.println("Received message (not processed yet): " + message.getPayload());
  }
}

Endpoint Config Check

You want to set up a WebSocket endpoint at the path /chat that allows connections from any origin and uses SockJS fallback. Which configuration snippet is correct?

Recap: WebSocket Endpoints

Great job! You've learned how to configure WebSocket endpoints in Spring Boot:

  • You use @EnableWebSocket on a @Configuration class.
  • You implement WebSocketConfigurer and override registerWebSocketHandlers.
  • Inside, you use registry.addHandler() to map a WebSocketHandler to a URL path.
  • Options like setAllowedOrigins() and withSockJS() enhance compatibility.

Next, we'll dive into how to send and receive messages using these handlers!

Frequently asked questions

Is the “WebSocket Endpoint Configuration” lesson free?

Yes — the full text of “WebSocket Endpoint Configuration” is free to read here on the web, and the WebSockets & Real-Time Systems with Spring course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the WebSockets & Real-Time Systems with Spring course, upgrade to CoddyKit PRO.

What will I learn in “WebSocket Endpoint Configuration”?

Configure WebSocket endpoints in Spring, defining paths and handling initial connections. You practise WebSockets & Real-Time Systems with Spring with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start WebSockets & Real-Time Systems with Spring?

No prior experience is required. WebSockets & Real-Time Systems with Spring on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “WebSocket Endpoint Configuration” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this WebSockets & Real-Time Systems with Spring lesson?

Yes. Every WebSockets & Real-Time Systems with Spring lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Spring Boot for WebSockets
  2. WebSocket Endpoint Configuration
  3. Basic Client-Server Messaging
  4. Handling WebSocket Lifecycle Events in Spring
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