webSocket-Java開發總結

websocket實現客戶端跟服務端的雙向傳輸，解決客戶端向服務端輪訓請求。應用到推送GPS位置信息，彈幕，聊天信息等場景。

一、Java服務端實現

maven依賴

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

核心服務代碼

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

}

主要是OnOpen OnClose OnMessage OnError方法，裏面再買上業務處理；


@Slf4j
@ServerEndpoint(value = "/websocket/user/{accessToken}")
@Component
@EnableScheduling
public class WebSocketUserServer {

    //靜態變量，用來記錄當前在線連接數。應該把它設計成線程安全的。
    private static AtomicInteger onlineCount = new AtomicInteger(0);
    //concurrent包的線程安全Set，用來存放每個客戶端對應的MyWebSocket對象。
    private static CopyOnWriteArrayList<UserSocket> userSockets = new CopyOnWriteArrayList<>();
    //與某個客戶端的連接會話，需要通過它來給客戶端發送數據
    private Session session;

    /*
    連接打開時執行
     */
    @OnOpen
    public void onOpen(@PathParam("accessToken") String accessToken , Session session) {

        open:{
            addOnlineCount();           //在線數加1
            this.session = session;
            log.info("WebSocketUserServer 有新連接加入！當前在線人數爲" + getOnlineCount());

            if(accessToken ==null || "".equals(accessToken)){
                log.info("WebSocketUserServer onOpen accessToken is null");
                closeSession(session);
                break open;
            }
            //校驗accessToken,獲取user信息
            //獲取service方法
            UcTokenFeign ucTokenFeign = SpringUtil.getBean(UcTokenFeign.class) ;
            ObjectRestResponse<UcTokenWebsocketVo> userResult = ucTokenFeign.getUserInfo(accessToken) ;
            if(userResult.getStatus() != CodeStatus.CODE_SUCCESS.getValue()
                    ||userResult.getData() == null){
                log.info("WebSocketUserServer onOpen token feign not success:"+userResult.getMsg());
                closeSession(session);
                break open;
            }

            //添加到用戶Session對應關係中
            UserSocket userSocket = new UserSocket();
            userSocket.setUserId(userResult.getData().getUserId())
            userSocket.setWebSocketUserServer(this);
            userSockets.add(userSocket) ;

//            try {
//                sendMessage("server連接成功");
//            } catch (IOException e) {
//                log.error("websocket IO異常");
//            }
            log.info("WebSocketUserServer Connected ... " + session.getId());
        }

    }

    /*
    服務端不接收非合規的client，進行關閉操作
     */
    private void closeSession(Session session){
        try {
            session.close();
        } catch (IOException e) {
            log.error("WebSocketUserServer close error:"+e);
            e.printStackTrace();
        }
    }

    /**
     * 連接關閉調用的方法
     */
    @OnClose
    public void onClose() {
        subOnlineCount();           //在線數減1
        log.info("WebSocketUserServer 有一連接關閉！當前在線人數爲" + getOnlineCount());

        userSockets.stream()
                .forEach(u ->{
                    if(u.getWebSocketUserServer() == this){
                        userSockets.remove(u) ;
                        log.info("WebSocketUserServer userSockets remove user socket,user:"+u.getUserId());
                    }
                } );

        log.info("WebSocketUserServer 刪除關閉連接的對應關係");
    }

    /**
     * 收到客戶端消息後調用的方法
     *
     * @param message 客戶端發送過來的消息*/
    @OnMessage
    public void onMessage(String message, Session session) {
        log.info("WebSocketUserServer 來自客戶端的消息:" + message);

//        //羣發消息
//        for (WebSocketUserServer 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("WebSocketUserServer 發生錯誤:"+error);
        error.printStackTrace();
    }

    /*
     給客戶端發送文本信息
     */
    public void sendMessage(String message) throws IOException {
        this.session.getBasicRemote().sendText(message);
        log.info("WebSocketUserServer sendMessage:"+message);
    }

    /*
    發送用戶狀態信息
     */
    public void sendUserPushMsgInfo(String status) throws IOException{
        this.session.getBasicRemote().sendText(status);
        log.info("WebSocketUserServer sendUserPushMsgInfo:"+status);
    }

    /*
    根據userID給客戶端推送用戶狀態
     */
    public static void PushMsgInfoToUser(String userId,String os
            ,String businessType,String status) throws IOException {
        if(status !=null && !"".equals(status)){
            userSockets.stream()
                    .forEach(u->{
                        if(u.getUserId().equals(userId)){
                            try {
                                u.getWebSocketUserServer().sendUserPushMsgInfo(status);
                                log.info("WebSocketUserServer PushMsgInfoToUser success,userId:"+userId);
                            } catch (IOException e) {
                                e.printStackTrace();
                                log.error("WebSocketUserServer PushMsgInfoToUser error,userId:"+userId);
                            }
                        }
                    });
        }

    }

    /*
    定時檢查存活的Session，如果未存活進行處理
     */
    @Scheduled(cron = "0 0/2 * * * ?")
    public static void checkAliveSession(){
        log.info("WebSocketUserServer checkAliveSession start:"+new Date());
        userSockets.stream()
                .forEach(u->{
                    if(!u.getWebSocketUserServer().session.isOpen()){
                        userSockets.remove(u) ;
                        log.info("WebSocketUserServer checkAlive remove not open session,userId:"+u.getUserId());
                    }
                });
        log.info("WebSocketUserServer checkAliveSession end:"+new Date());
    }

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

    public static synchronized void addOnlineCount() {
        WebSocketUserServer.onlineCount.getAndIncrement();
    }

    public static synchronized void subOnlineCount() {
        WebSocketUserServer.onlineCount.getAndDecrement();
    }
}

二、websocket服務中引入service服務

採用輔助工具類SpringUtil獲取Bean,

UcTokenFeign ucTokenFeign = SpringUtil.getBean(UcTokenFeign.class) ;

@Component
public class SpringUtil implements ApplicationContextAware {

    private static ApplicationContext applicationContext;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        if(SpringUtil.applicationContext == null) {
            SpringUtil.applicationContext = applicationContext;
        }
    }

    //獲取applicationContext
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }

    //通過name獲取 Bean.
    public static Object getBean(String name){
        return getApplicationContext().getBean(name);
    }

    //通過class獲取Bean.
    public static <T> T getBean(Class<T> clazz){
        return getApplicationContext().getBean(clazz);
    }

    //通過name,以及Clazz返回指定的Bean
    public static <T> T getBean(String name,Class<T> clazz){
        return getApplicationContext().getBean(name, clazz);
    }
}

三、websocket的分佈式實現

1.session 放到redis中，實現數據共享，但是websocket session不支持序列號，存儲不了
2.加入消息中間件，實現收到消息後的共享

consumer有兩種消費模式：集羣消費和廣播消費。集羣消費：多個consumer平均消費該topic下所有mq的消息，即某個消息在某個message queue中被一個consumer消費後，其他消費者就不會消費到它；廣播消費：所有consumer可以消費到發到這個topic下的所有消息。

因爲Session不支持序列化，nginx分發不能保證一定指定到同一臺服務器，特別移動互聯網，移動設備下。

故採用消息訂閱模式進行實現。每臺服務器都訂閱相同主題的消息，接收到消息後，關聯到session則進行推送消息。

CopyOnWriteArrayList<UserSocket> userSockets = new CopyOnWriteArrayList<>() 這裏便是維護關係點

四、客戶端調用的html測試代碼

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>WebSocket Chat</title>
</head>
<body>
	<script type="text/javascript">
		var socket;
		if (!window.WebSocket) {
			window.WebSocket = window.MozWebSocket;
		}
		if (window.WebSocket) {
			socket = new WebSocket("ws://127.0.0.1:8877/websocket/user1/qw");
			socket.onmessage = function(event) {
				var ta = document.getElementById('responseText');
				ta.value = ta.value + '\n' + event.data
			};
			socket.onopen = function(event) {
				var ta = document.getElementById('responseText');
				ta.value = "連接開啓!";
			};
			socket.onclose = function(event) {
				var ta = document.getElementById('responseText');
				ta.value = ta.value + "連接被關閉";
			};
		} else {
			alert("你的瀏覽器不支持 WebSocket！");
		}
 
		function send(message) {
			if (!window.WebSocket) {
				return;
			}
			if (socket.readyState == WebSocket.OPEN) {
				socket.send(message+ new Date());
			} else {
				alert("連接沒有開啓.");
			}
		}

		function userclose(){
			if (!window.WebSocket) {
				return;
			}
			if (socket.readyState == WebSocket.OPEN) {
				socket.close() ;
			} else {
				alert("連接沒有開啓.");
			}
		}
	</script>
	<form onsubmit="return false;">
		<h3>WebSocket 聊天室1：</h3>
		<textarea id="responseText" style="width: 500px; height: 300px;"></textarea>
		<br> 
		<input type="button" onclick="send('first send message')" value="btnSend">
		<input type="button" onclick="userclose()" value="btnClose">
	</form>
	</body>
</html>

五、nginx配置

upstream websocket {
       server 1.203.115.27:8877;
       server 127.0.0.1:8877;   
    }

    server {
        listen 8888;
        location / {
            proxy_pass http://websocket;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "upgrade";
        }
    }

六、zuul負載websocket

spring cloud zuul 1.x版本臨時不直接支持spring websocket，到2.×版本會支持。

1.x版本也可以支持websocket，配置比較麻煩，需要結合sock.js stomp等。詳細可以參考該網站：https://stackoverflow.com/questions/39472635/zuul-with-web-socket

七、斷網、弱網、切換網等場景，實際使用的問題處理

待補充

八、websocket發送消息支持的長度大小

下面代碼循環執行50000次，前端還可以接收到，不過已經需要好幾秒的時間，這個時間延遲已經不低。

10W次也可以接收到，已經延遲到幾分鐘的程度。

循環次數 length

10000 33400
20000 66800
50000 16700011

100000 33400011

StringBuffer msg =new StringBuffer()  ;
//                {"centerLat":"27.403234","centerLon":"117.504426","maxLat":"31.849878","maxLon":"121.434785","minLat":"22.956590","minLon":"113.574066","locations":[{"lon":"121.434785","lat":"31.849878","vehicleNo":"京AA8866","transportStatus":"0"},{"lon":"113.574066","lat":"22.956590","vehicleNo":"京ETYUUII","transportStatus":"0"}]}

                for(int i=0;i<100000;i++){
                    msg.append( "                {\"centerLat\":\"27.403234\",\"centerLon\":\"117.504426\",\"maxLat\":\"31.849878\"" +
                            ",\"maxLon\":\"121.434785\",\"minLat\":\"22.956590\",\"minLon\":\"113.574066\"" +
                            ",\"locations\":[{\"lon\":\"121.434785\",\"lat\":\"31.849878\",\"vehicleNo\":\"京AA8866\",\"transportStatus\":\"0\"}" +
                            ",{\"lon\":\"113.574066\",\"lat\":\"22.956590\",\"vehicleNo\":\"京ETYUUII\",\"transportStatus\":\"0\"}]}\n"
                    );
                }
                sendMessage("server連接成功;"+msg.toString());

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