pom文件

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

java文件

启用WebSocket

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

@Configuration  
public class WebSocketConfig {  
    
    @Bean  
    public ServerEndpointExporter serverEndpointExporter() {  
        return new ServerEndpointExporter();  
    }  
  
}

增加工具类WebSocketServer

import java.io.IOException;
import java.util.concurrent.CopyOnWriteArraySet;

import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.ServerEndpoint;
import org.springframework.stereotype.Component;
import cn.hutool.log.Log;
import cn.hutool.log.LogFactory;
import lombok.extern.slf4j.Slf4j;


@ServerEndpoint("/websocket/{sid}")
@Component
public class WebSocketServer {
    
    static Log log=LogFactory.get(WebSocketServer.class);
    //静态变量，用来记录当前在线连接数。应该把它设计成线程安全的。
    private static int onlineCount = 0;
    //concurrent包的线程安全Set，用来存放每个客户端对应的MyWebSocket对象。
    private static CopyOnWriteArraySet<WebSocketServer> webSocketSet = new CopyOnWriteArraySet<WebSocketServer>();

    //与某个客户端的连接会话，需要通过它来给客户端发送数据
    private Session session;

    //接收sid
    private String sid="";
    /**
     * 连接建立成功调用的方法*/
    @OnOpen
    public void onOpen(Session session,@PathParam("sid") String sid) {
        this.session = session;
        webSocketSet.add(this);     //加入set中
        addOnlineCount();           //在线数加1
        log.info("有新窗口开始监听:"+sid+",当前在线人数为" + getOnlineCount());
        this.sid=sid;
        try {
             sendMessage("连接成功");
        } catch (IOException e) {
            log.error("websocket IO异常");
        }
    }

    /**
     * 连接关闭调用的方法
     */
    @OnClose
    public void onClose() {
        webSocketSet.remove(this);  //从set中删除
        subOnlineCount();           //在线数减1
        log.info("有一连接关闭！当前在线人数为" + getOnlineCount());
    }

    /**
     * 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) {
        log.info("收到来自窗口"+sid+"的信息:"+message);
        //群发消息
        for (WebSocketServer item : webSocketSet) {
            try {
                item.sendMessage(message);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 
     * @param session
     * @param error
     */
    @OnError
    public void onError(Session session, Throwable error) {
        log.error("发生错误");
        error.printStackTrace();
    }
    /**
     * 实现服务器主动推送
     */
    public void sendMessage(String message) throws IOException {
        this.session.getBasicRemote().sendText(message);
    }


    /**
     * 群发自定义消息
     * */
    public static void sendInfo(String message,@PathParam("sid") String sid) throws IOException {
        log.info("推送消息到窗口"+sid+"，推送内容:"+message);
        for (WebSocketServer item : webSocketSet) {
            try {
                //这里可以设定只推送给这个sid的，为null则全部推送
                if(sid==null) {
                    item.sendMessage(message);
                }else if(item.sid.equals(sid)){
                    item.sendMessage(message);
                }
            } catch (IOException e) {
                continue;
            }
        }
    }

    public static synchronized int getOnlineCount() {
        return onlineCount;
    }

    public static synchronized void addOnlineCount() {
        WebSocketServer.onlineCount++;
    }

    public static synchronized void subOnlineCount() {
        WebSocketServer.onlineCount--;
    }
}

消息推送

推送新信息，可以再自己的Controller写个方法调用WebSocketServer.sendInfo();即可

@Controller
@RequestMapping("/checkcenter")
public class CheckCenterController {
    //推送数据接口
    @ResponseBody
    @RequestMapping("/socket/push/{cid}")
    public ApiReturnObject pushToWeb(@PathVariable String cid,String message) {  
        try {
            WebSocketServer.sendInfo(message,cid);
        } catch (IOException e) {
            e.printStackTrace();
            return ApiReturnUtil.error(cid+"#"+e.getMessage());
        }  
        return ApiReturnUtil.success(cid);
    } 
}

页面发起socket请求

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>webSocketTest客户端</title>
</head>

<body>
    
        <h4>客户端输入：</h4>
        <textarea id = "message" name="message" style="width: 200px;height: 100px"></textarea>
        <br/>
        <input type="button" value="发送到服务器" onclick="sendMessage()" />
    
 
        <h4>服务器返回消息：</h4>
        <textarea id = "responseText" name="message" style="width: 1100px;height: 100px"></textarea>
        <br/>
        <input type="button" οnclick="javascript:document.getElementById('responseText').value=''" value="clear data">
 <script type="text/javascript">
    function send(){
        alert(2);
    }
    var webSocket;
    if(window.WebSocket){
        webSocket = new WebSocket("ws://localhost:21270/websocket/1");
        //客户端收到服务器的方法，这个方法就会被回调
        webSocket.onmessage = function (ev) {
        
            var contents = document.getElementById("responseText");
            contents.value = contents.value +"\n"+ ev.data;
        }
 
        webSocket.onopen = function (ev) {
            var contents = document.getElementById("responseText");
            contents.value = "与服务器端的websocket连接建立";
            
            var data = '{"method":"init","identifier":"11VKF7M0020199"}';
            
            webSocket.send(data);
        }
        webSocket.onclose = function (ev) {
            
            var contents = document.getElementById("responseText");
            contents.value =  contents.value +"\n"+ "与服务器端的websocket连接断开";
        }
    }else{
        alert("该环境不支持websocket")
    }
 
    function sendMessage() {
        //alert(document.getElementById("message").value);
        if(window.webSocket){
            if(webSocket.readyState == WebSocket.OPEN){
                
                webSocket.send(document.getElementById("message").value);
            }else{
                alert("与服务器连接尚未建立")
            }
        }
    }
    
    
</script>   
</body>
</html>