在Java中，我們可以使用Spring Boot框架和WebSocket庫來實現消息廣播。以下是實現WebSocket消息廣播的步驟：
在你的pom.xml文件中添加Spring Boot和WebSocket的依賴：
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-websocket</artifactId>
</dependency>
</dependencies>
創建一個配置類WebSocketConfig，繼承AbstractWebSocketMessageBrokerConfigurer，并配置WebSocket的端點和消息代理：
@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig extends AbstractWebSocketMessageBrokerConfigurer {
@Override
public void configureMessageBroker(MessageBrokerRegistry config) {
config.enableSimpleBroker("/topic");
config.setApplicationDestinationPrefixes("/app");
}
@Override
public void registerStompEndpoints(StompEndpointRegistry registry) {
registry.addEndpoint("/websocket").withSockJS();
}
}
創建一個控制器WebSocketController，用于處理客戶端發送的消息并將其廣播到所有訂閱了相應主題的客戶端：
@Controller
public class WebSocketController {
@MessageMapping("/broadcast")
@SendTo("/topic/messages")
public String broadcastMessage(@Payload String message) {
return "廣播消息: " + message;
}
}
在你的前端應用中，使用JavaScript和SockJS庫連接到WebSocket服務器并發送/接收消息。以下是一個簡單的示例：
<!DOCTYPE html>
<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/sockjs-client/1.5.0/sockjs.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/stomp.js/2.3.3/stomp.min.js"></script>
</head>
<body>
<script>
// 連接到WebSocket服務器
var socket = new SockJS('/websocket');
var stompClient = Stomp.over(socket);
stompClient.connect({}, function (frame) {
console.log('Connected: ' + frame);
// 訂閱消息主題
stompClient.subscribe('/topic/messages', function (response) {
console.log('Received message: ' + response.body);
});
// 發送廣播消息
stompClient.send("/app/broadcast", {}, 'Hello, WebSocket!');
});
</script>
</body>
</html>
現在，當客戶端發送消息到/app/broadcast端點時，WebSocketController將接收到消息并將其廣播到所有訂閱了/topic/messages主題的客戶端。
