Real-Time Communication: Implementing WebSockets in Spring Boot

The Need for Real-Time Data

In modern web applications, forcing users to refresh a page or continuously polling a server for new data is incredibly inefficient. Whether you are building a live trading dashboard, a collaborative document editor, or a scalable chat application, you need persistent, two-way communication. This is where WebSockets outshine standard HTTP requests.

HTTP vs. WebSockets

Traditional HTTP is strictly unidirectional (client requests, server responds) and stateless. WebSockets, on the other hand, establish a persistent, full-duplex connection over a single TCP socket. Once the connection is upgraded from HTTP to WebSocket, both the client and server can push messages to each other instantly.

Configuring WebSockets in Spring Boot

Spring Boot makes implementing WebSockets remarkably straightforward. The first step is adding the spring-boot-starter-websocket dependency. Then, you define a configuration class implementing WebSocketConfigurer.

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(new ChatWebSocketHandler(), "/chat")
                .setAllowedOrigins("*");
    }
}
      

Handling the Messages

Next, you create a handler by extending TextWebSocketHandler. This is where you manage incoming connections, handle text messages, and broadcast updates to connected sessions.

• afterConnectionEstablished: Triggered when a user connects. Store their session.
• handleTextMessage: Triggered when a payload is received. Parse the JSON and broadcast it.
• afterConnectionClosed: Remove the session to prevent memory leaks.

Scaling Considerations

While an in-memory session list works for a single instance, scaling horizontally requires a different approach. In live production environments using Docker and AWS EC2, you must integrate a message broker like Redis Pub/Sub or RabbitMQ to route WebSocket messages across multiple Spring Boot instances.

Image credit: Unsplash