WebSockets Real-Time

Add the WebSocket dependency.

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-websocket</artifactId>
</dependency>

1. WebSocket Configuration (WebSocketConfig.java)

package com.devinhyderabad;

import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {

    @Override
    public void configureMessageBroker(MessageBrokerRegistry config) {
        // 1. Messages sent to "/topic" will be broadcast to all subscribers
        config.enableSimpleBroker("/topic");
        // 2. Messages sent by clients should be prefixed with "/app"
        config.setApplicationDestinationPrefixes("/app");
    }

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        // 3. The frontend connects to this endpoint (like a REST API URL)
        registry.addEndpoint("/ws-chat").withSockJS();
    }
}

2. The Chat Controller (ChatController.java)

package com.devinhyderabad;

import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.messaging.handler.annotation.SendTo;
import org.springframework.stereotype.Controller;

@Controller
public class ChatController {

    // 1. When a message arrives at "/app/sendMessage"
    @MessageMapping("/sendMessage")
    // 2. The return value is broadcast to everyone listening on "/topic/messages"
    @SendTo("/topic/messages")
    public ChatMessage broadcastMessage(ChatMessage message) {
        return message;
    }
}

class ChatMessage {
    private String sender;
    private String content;
    
    public String getSender() { return sender; }
    public void setSender(String sender) { this.sender = sender; }
    public String getContent() { return content; }
    public void setContent(String content) { this.content = content; }
}