1.引入websocket依賴

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

2.添加配置文件WebSocketConfig.class

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

3.實(shí)現(xiàn)消息通知類WebSocketServer.class

@Component
@ServerEndpoint(value = "/websocket/{id}")
public class WebSocketServer {
    private static int onlineCount = 0;
    private static ConcurrentHashMap<String, WebSocketServer> webSocketMap = new ConcurrentHashMap<>();
    //與某個(gè)客戶端的連接會(huì)話，需要通過它來(lái)給客戶端發(fā)送數(shù)據(jù)
    private Session session;
    private static Logger log = LogManager.getLogger(WebSocketServer.class);
    private String id = "";

    /**
     * 連接建立成功調(diào)用的方法
     * @param id 用戶的標(biāo)識(shí)
     * @param session 會(huì)話
     */
    @OnOpen
    public void onOpen(@PathParam(value = "id") String id, Session session) {
        //設(shè)置超時(shí)時(shí)間
        session.setMaxIdleTimeout(3600000);
        this.session = session;
        //接收到發(fā)送消息的人員編號(hào)
        this.id = id;
        //加入set中
        if (webSocketMap.containsKey(id)){
            webSocketMap.remove(id);
        }
        webSocketMap.put(id, this);
        //在線數(shù)加1
        addOnlineCount();
        log.info("用戶"+id+"加入缕粹！當(dāng)前在線人數(shù)為" + getOnlineCount());

        try {
            sendMessage("連接成功");
        } catch (IOException e) {
            log.error("websocket IO異常");
        }
    }

    /**
     * 連接關(guān)閉調(diào)用的方法
     */
    @OnClose
    public void onClose() {
        //從map中刪除
        webSocketMap.remove(this.id);
        //在線數(shù)減1
        subOnlineCount();
        log.info("有一連接關(guān)閉叉弦！當(dāng)前在線人數(shù)為" + getOnlineCount());
    }

    /**
     * 收到客戶端消息后調(diào)用的方法
     * @param message 客戶端發(fā)送過來(lái)的消息
     * @param session 會(huì)話
     * */
    @OnMessage
    public void onMessage(String message, Session session) {
        log.info("來(lái)自客戶端的消息:" + message);
        //可以自己約定字符串內(nèi)容耕漱，比如 內(nèi)容|0 表示信息群發(fā)潜慎，內(nèi)容|X 表示信息發(fā)給id為X的用戶
        String sendMessage = message.split("[|]")[0];
        String sendUserId = message.split("[|]")[1];
        try {
            if(sendUserId.equals("0")) {
                sendtoAll(sendMessage);
            }
            else {
                sendMessageTo(sendMessage, sendUserId);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    /**
     *
     * @param session
     * @param error
     */
    @OnError
    public void onError(Session session, Throwable error) {
        log.error("發(fā)生錯(cuò)誤");
        error.printStackTrace();
    }


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

    public void sendMessageTo(String message,String sendUserId) throws IOException{
        if (webSocketMap.get(sendUserId) != null) {
            if(!id.equals(sendUserId)){
                webSocketMap.get(sendUserId).sendMessage( "用戶" + id + "發(fā)來(lái)消息：" + " <br/> " + message);
            }
            else {
                webSocketMap.get(sendUserId).sendMessage(message);
            }
        } else {
            //如果用戶不在線則返回不在線信息給自己
//            sendtoUser("當(dāng)前用戶不在線",id);
        }
    }



    /**
     * 發(fā)送信息給所有人
     * @param message
     * @throws IOException
     */
    public void sendtoAll(String message) throws IOException {
        for (String key : webSocketMap.keySet()) {
            try {
                webSocketMap.get(key).sendMessage(message);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }


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

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

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

4.測(cè)試
前端js訪問http://localhost:8080/websocket/123