1、依赖

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

2、使用

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div style="padding: 40px">
    <font color="black" ><strong>账户登录测试</strong></font><br><br>
    账号<input id="username" type="text"><br>
    密码<input id="password" type="text"><br><br>
    <input type="button" value="登录" >
    <input type="button" value="注册" style="margin-left: 60px">
</div><br>
<div style="padding: 40px">
    <font color="black" ><strong>扫码登录测试</strong></font><br><br>
    <img src="${url}" style="width: 100px;height: 100px"/></a><br>
</div>
</body>

<script>
    var token;
    if( typeof(WebSocket) == "undefined"){
        alert("您的浏览器不支持websocket")
    }else {
        alert("您的浏览器支持websocket")
        socket = new WebSocket("ws://127.0.0.1/websocket/".replace("http","ws"));

        socket.onopen = function () {
            console.log("socket已打开")
            socket.send("[[${code}]]")
        };

        socket.onmessage = function (msg){
            token = JSON.parse(msg.data).data();
            console.log("TOKEN获取成功",token);
        };

        socket.close =function (){
            console.log("socket已关闭")
        };

        socket.onerror = function (){
            console.log("socket发生了错误，请刷新")
        }
    }
</script>
</html>


@Component
@ServerEndpoint("/websocket/")
public class WebSocketServer {
    static Logger log = LoggerFactory.getLogger(WebSocketServer.class);
    //静态变量，用来记录当前在线连接数。
    private static AtomicInteger onlineCount = new AtomicInteger(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<>();
    //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;
    private String code;

    /**
     * 建立连接成功调用的方法
     * @param session
     */
    @OnOpen
    public void onOpen(Session session) {
        this.session = session;
        webSocketSet.add(this);
        addOnlineCount();
        log.info("有新请求链接进入,当前在线人数为" + getOnlineCount());
    }


    @OnClose
    public void onClose(){
        webSocketSet.remove(this);
        subOnlineCount();           //在线数减1
        log.info("有一连接关闭！当前在线人数为" + getOnlineCount());
    }

    @OnMessage
    public void onMessage(String message, Session session){
        log.info("收到来自窗口的信息,Code为:" + message);

        //群发消息
        for (WebSocketServer item : webSocketSet) {
            if(item.session == item.session){
                //存储code
                item.code = message;
            }
        }
    }

    /**
     *
     * @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
     * @param message
     * @throws IOException
     */
    public void sendMessage(String message) throws IOException {
        this.session.getBasicRemote().sendText(message);
    }

    public static void sendInfo(String message, String code){
        log.info("推送消息到窗口" + code + "，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(code == null){
                    item.sendMessage(message);
                }else if(item.code == code){
                    item.sendMessage(message);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void subOnlineCount() {
        WebSocketServer.onlineCount.decrementAndGet();
    }

    private static int getOnlineCount() {
        return onlineCount.get();
    }

    public void addOnlineCount() {
        WebSocketServer.onlineCount.incrementAndGet();
    }
}