1.添加pom依赖

        <!-- WebSocket完成订单通知 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-websocket</artifactId>
        </dependency>

2.代码

后端

package com.rocketmq.ws;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;

/**
 * @author liudean
 * @date 2022/1/11 14:54
 */
@Configuration
public class WebSocketConfig {
    @Bean
    public ServerEndpointExporter serverEndpointExporter() {
        return new ServerEndpointExporter();
    }
}

package com.rocketmq.ws;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONObject;

import javax.websocket.Encoder;
import javax.websocket.EndpointConfig;

/**
 * @author liudean
 * 自定义返回格式
 * @date 2022/1/11 14:54
 */
public class ServerEncoder implements Encoder.Text<JSONObject> {
    @Override
    public String encode(JSONObject jsonObject){
        return JSON.toJSONString(jsonObject);
    }

    @Override
    public void init(EndpointConfig endpointConfig) {

    }

    @Override
    public void destroy() {

    }
}

package com.rocketmq.ws;

import com.alibaba.fastjson.JSON;
import com.rocketmq.common.ResultMsg;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.concurrent.ConcurrentHashMap;

/**
 * @author liudean
 * @date 2022/1/11 14:52
 */
@Component
@ServerEndpoint(value = "/websocket/{uuid}",encoders = ServerEncoder.class)
public class WebSocketServer {
    public static ConcurrentHashMap<String, Session> clients = new ConcurrentHashMap<>();

    private final Logger log = LoggerFactory.getLogger("WebSocketServer");

    /**
     * 连接建立成功调用的方法
     * */
    @OnOpen
    public void onOpen(Session session, @PathParam("uuid") String uuid) {
        log.info("客户端：" + uuid + "连接成功了");
        clients.put(uuid, session);
    }

    /**
     * 连接关闭调用的方法
     */
    @OnClose
    public void onClose(@PathParam("uuid") String uuid) {
        log.info("客户端：" + uuid + "断开连接了");
        clients.remove(uuid);
    }

    /**
     * 收到客户端消息后调用的方法
     *
     * @param message 客户端发送过来的消息*/
    @OnMessage
    public void onMessage(String message, Session session) {
        System.out.println("收到客户端消息:"+message);

    }
    @OnError
    public void one rror(Throwable error) {
        error.printStackTrace();
    }


    /**
     * 测试
     * 实现服务器主动推送
     * 之后方法里面可通过建立连接的uuid推送到客户端
     */
    public void sendMessage(String uuid) throws IOException, EncodeException {
        Session session = WebSocketServer.clients.get(uuid);
        if (session != null) {
            System.out.println("连接成功，处理返回"+uuid);
            session.getBasicRemote().sendObject(JSON.toJSON(ResultMsg.SUCCESS.setNewData("我草，成功了")));
        } else {
            System.out.println("找不到客户端："+uuid+"的连接");
        }
    }
}

前端

<template>
    <div>
        <el-row>
            <el-button type="success"  @click="onSubmit">成功按钮</el-button>
        </el-row>
    </div>
</template>
<script>

export default {
  data() {
    return {

    };
  },
  mounted() {

  },
  methods: {
    onSubmit() {
        let uuid = "8246666666"
          this.$axios
            .post("/send", {
              uuid: uuid,
            })
            .then((res) => {
              console.log(res);
              if (res.data.resultCode === 200) {
                //建立连接
                this.createSocket(uuid);
              } else {
                  alert(1)
              }
            });
    },
    createSocket(uuid){
    var socket;
    if(typeof(WebSocket) == "undefined") {
        console.log("您的浏览器不支持WebSocket");
    }else{
        //实现化WebSocket对象，指定要连接的服务器地址与端口  建立连接
        let socketUrl = "ws://192.168.3.254:8021/websocket/" + uuid;
          if (socket != null) {
            socket.close();
            socket = null;
          }
          // 开启一个websocket服务
        socket = new WebSocket(socketUrl);
        //打开事件
        socket.onopen = function() {
            console.log("Socket 已打开");
            //socket.send("这是来自客户端的消息" + location.href + new Date());
        };
        //获得消息事件
        //浏览器端收消息，获得从服务端发送过来的文本消息
        socket.onmessage = function(event) {
            console.log("返回了");
            console.log(event);
            var result = $.parseJSON(event.data);
            if(result.code === 200){
                
            }else{
                layer.msg(result.msg);
            }
        };
        //关闭事件
        socket.onclose = function() {
            console.log("Socket已关闭");
        };
        //发生了错误事件
        socket.onerror = function() {
            console.log("Socket发生了错误");
        }
        //窗口关闭
        $(window).unload(function(event){
            socket.close();
        });
    }
    return socket;
}
  },
};
</script>