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

@Component
public class WebSocketAPI extends TextWebSocketHandler {
    @Override //該方法會在websocket連接成功后被調(diào)用
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        //WebSocketSession是websocket連接對應的會話
        System.out.println("建立連接了");
    }
    @Override //該方法是在websocket收到消息的時候自動調(diào)用
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
        //message 為收到的消息
        System.out.println("發(fā)送消息："+message.toString());
        //session是個會話，里面記錄了通信雙方,通過session對象調(diào)用send方法實現(xiàn)服務器推送消息
        session.sendMessage(message);
        message.getPayload(); //獲取的message字符串
    }
    @Override //該方法是在websocket連接出現(xiàn)異常的時候自動調(diào)用的
    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        //exception記錄了異常信息
        System.out.println("連接出現(xiàn)異常了");
    }
    @Override //該方法是在websocket連接關(guān)閉后自動調(diào)用的
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        //status 為關(guān)閉的狀態(tài)
        System.out.println("連接關(guān)閉了");
    }
}

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
    @Autowired
    private WebSocketAPI webSocketAPI;
    @Override //通過該方法，把創(chuàng)建好的Handler類注冊到具體的路徑上
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        //當瀏覽器，websocket的請求路徑是/test的時候，就會調(diào)用到webSocketTest中的方法
        registry.addHandler(webSocketAPI,"/websocketMessage");
    }
}

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
    @Autowired
    private WebSocketAPI webSocketAPI;
    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry.addHandler(webSocketAPI,"/websocketMessage").
                // 通過注冊特定的HttpSession攔截器，就可以把
                // 用戶給HttpSession中添加的Attribute鍵值對，往WebSocketSession中也添加一份
                addInterceptors(new HttpSessionHandshakeInterceptor());
    }
}

    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        User user = (User)session.getAttributes().get("user");
        System.out.println("建立連接");
    }

@Component
public class WebSocketSessionManage {
    private ConcurrentHashMap<Integer, WebSocketSession> websocketSessions = new ConcurrentHashMap<>();
    //用戶連接，添加連接關(guān)系
    public void addWebSocketSession(Integer userId,WebSocketSession webSocketSession){
        //用戶已經(jīng)上線，防止多開
        if(websocketSessions.containsKey(userId)){
            return;
        }
        websocketSessions.put(userId,webSocketSession);
    }
    //用戶掉線，刪除連接關(guān)系
    public void delWebSocketSession(Integer userId,WebSocketSession webSocketSession){
        WebSocketSession get = websocketSessions.get(userId);
        //只有關(guān)系中存在自己的連接信息，才刪除
        if(get == webSocketSession){
            websocketSessions.remove(userId);
        }
    }
    //根據(jù)用戶id獲取WebSocketSession
    public WebSocketSession getWebSocketSession(Integer userId){
        return websocketSessions.get(userId);
    }
}

 //websocket傳輸消息
	 //創(chuàng)建websocket實例
	let websocket = new WebSocket("ws://" + location.host + "/websocketMessage");
	//綁定一些函數(shù)
	websocket.onopen = function(){
	    console.log('建立連接')
	}
	websocket.onmessage = function(e){
	    //e.data為收到服務端推送的消息
	    //e.data為一個json字符串，可以使用JSON.prase(e.data)轉(zhuǎn)換為js對象
	    let resp = JSON.prase(e.data);
	    console.log('收到消息：'+resp)
	}
	websocket.onerror = function(){
	    console.log('出現(xiàn)異常')
	}
	websocket.onclose = function(){
	    console.log('關(guān)閉連接')
	}
	//使用websocket實例調(diào)用send方法即可向服務器發(fā)送消息
	//注意：參數(shù)為字符串，不能為js對象
	//要發(fā)送json格式的數(shù)據(jù)，將json對象序列化為字符串，JSON.stringfy(json)
	websocket.send("hehe");