第一步：配置Spring

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-messaging</artifactId>
</dependency>

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

第二步：配置WebSocket

我采用的是使用Configurer类和 Annotation来进行WebSocket配置。
首先要创建一个类，继承WebSocketMessageBrokerConfigurer 或者继承AbstractSecurityWebSocketMessageBrokerConfigurer，并且在类上加上annotation：@Configuration和@EnableWebSocketMessageBroker。这样，Spring就会将这个类当做配置类，并且打开WebSocket。

AbstractSecurityWebSocketMessageBrokerConfigurer这个类在spring-security-config这个包中
 

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.simp.config.ChannelRegistration;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.security.config.annotation.web.messaging.MessageSecurityMetadataSourceRegistry;
import org.springframework.security.config.annotation.web.socket.AbstractSecurityWebSocketMessageBrokerConfigurer;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
import org.springframework.web.socket.config.annotation.WebSocketTransportRegistration;

@Configuration
@EnableWebSocketMessageBroker
@EnableConfigurationProperties(StompWebSocketProperties.class)
public class StompWebSocketConfig extends AbstractSecurityWebSocketMessageBrokerConfigurer {

    @Autowired
    private StompWebSocketProperties stompWebSocketProperties;

    //添加这个Endpoint，这样在网页中就可以通过websocket连接上服务了
    @Override
    public void registerStompEndpoints(StompEndpointRegistry stompEndpointRegistry) {
        stompEndpointRegistry.addEndpoint("endpoint").setAllowedOrigins("*").withSockJS();
    }

    /**
     * 配置消息代理
     *
     * @param registry
     */
    @Override
    public void configureMessageBroker(MessageBrokerRegistry registry) {
         System.out.println("服务器启动成功");
        //这里设置的simple broker是指可以订阅的地址，也就是服务器可以发送的地址
        registry.enableSimpleBroker("/topic");
        registry.setUserDestinationPrefix("/user");
        
    }

    @Override
    protected boolean sameOriginDisabled() {
        return true;
    }

    /**
     * 消息传输参数配置
     */
    @Override
    public void configureWebSocketTransport(WebSocketTransportRegistration registry) {
        // 设置消息字节数大小
        registry.setMessageSizeLimit(stompWebSocketProperties.getMessageSizeLimit())
            // 设置消息缓存大小x
            .setSendBufferSizeLimit(stompWebSocketProperties.getSendBufferSizeLimit())
            // 设置消息发送时间限制毫秒
            .setSendTimeLimit(stompWebSocketProperties.getSendTimeLimit());
    }

    /**
     * 业务需要自定义
     */
    @Override
    protected void configureInbound(MessageSecurityMetadataSourceRegistry messages) {
        messages.anyMessage().permitAll();
    }

    /**
     * 输出通道参数设置
     */
    @Override
    public void configureClientOutboundChannel(ChannelRegistration registration) {
        registration.taskExecutor().corePoolSize(stompWebSocketProperties.getCorePoolSize())
            .maxPoolSize(stompWebSocketProperties.getMaxPoolSize())
            .keepAliveSeconds(stompWebSocketProperties.getKeepAliveSeconds());
    }

}

configureMessageBroker 方法用于配置消息代理，registerStompEndpoints 方法用于注册 WebSocket 端点。enableSimpleBroker("/topic") 表示启用简单的消息代理，并将消息发送到 /topic 目的地。addEndpoint("/endpoint").withSockJS() 表示注册一个 WebSocket 端点，并启用 SockJS 支持

定义一个发送消息的类：前端订阅后，后端 有消息时，可以通过此方法发送到前端

import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.messaging.simp.SimpMessagingTemplate;
import org.springframework.stereotype.Component;

@Component
public class StompMsgSendMessage {

    @Autowired
    private SimpMessagingTemplate messagingTemplate;

    public void sendMsgToClient(String topic, Object o) {
        if (StringUtils.isBlank(topic)) {
            return;
        }
        messagingTemplate.convertAndSend(topic, o);
    }
}

前端使用的是：SockJS和Stomp实现websocket

<!DOCTYPE html>
<html>
<head>
    <title>Chat Room</title>
    <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>
    <div id="chatroom">
        <ul id="messages"></ul>
    </div>
    <form id="form">
        <input type="text" id="input" placeholder="Type your message here...">
        <button type="submit">Send</button>
    </form>
    <script>
        var socket = new SockJS('http://localhost:8080/TESTAPP/endpoint');
        var stompClient = Stomp.over(socket);
        var messagesElement = document.getElementById('messages');
        var formElement = document.getElementById('form');
        var inputElement = document.getElementById('input');

        stompClient.connect({}, function (frame) {
            console.log('Connected: ' + frame);
            stompClient.subscribe('/topic/device/upgrade', function (message) {
                var li = document.createElement('li');
                li.appendChild(document.createTextNode(message.body));
                messagesElement.appendChild(li);
            });
        });

        formElement.addEventListener('submit', function (event) {
            event.preventDefault();
            stompClient.send("/send", {}, inputElement.value);  //后端需要写controller方法接收消息
            inputElement.value = '';
        });
    </script>
</body>
</html>

后端Controller中模拟发消息 到前端的订阅地址：topic/device/upgrade 

@Autowired
    private StompMsgSendMessage stompMsgSendMessage;
    @GetMapping("/upgradeok")
    public ResponseMessage<String> upgradeok() {
        log.info("######测试出发升级完成的通知");
        stompMsgSendMessage.sendMsgToClient("/topic/device/upgrade", "upgarde sunccess "+ new Date());
        return ResponseMessage.ok("ok");
    }

测试结果：

后端服务启动后，打开html页面：

websocket连接成功

消息订阅：

postman调用controller中方法模拟发消息：