Springboot-websocket实现及底层原理

在Spring Boot中实现WebSocket功能，你可以使用Spring的@EnableWebSocketMessageBroker注解来配置一个WebSocket消息代理。以下是一个简单的例子：

1. 添加Maven依赖：

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

2. 配置WebSocketMessageBroker：

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 registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/ws").withSockJS();
    }
 
    @Override
    public void configureMessageBroker(MessageBrokerRegistry registry) {
        registry.enableSimpleBroker("/topic");
        registry.setApplicationDestinationPrefixes("/app");
    }
}

3. 创建控制器来处理WebSocket消息：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.messaging.handler.annotation.SendTo;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
 
@Controller
public class WebSocketController {
 
    @MessageMapping("/hello")
    @SendTo("/topic/greetings")
    public String greeting(String message) {
        return "Hello, " + message + "!";
    }
}

4. 在前端使用WebSocket：

<script src="https://cdn.jsdelivr.net/npm/sockjs-client@1.7.0/dist/sockjs.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/stompjs@2.3.3/stomp.min.js"></script>
<script type="text/javascript">
    var socket = new WebSocket('ws://' + window.location.host + '/ws');
    var stompClient = Stomp.over(socket);
    stompClient.connect({}, function(frame) {
        console.log('Connected: ' + frame);
        stompClient.subscribe('/topic/gr