SpringBoot集成WebSocket實現服務器端主動推送

步驟

1. maven配置依賴

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

2. 編寫WebSocketConfig配置文件，開啓websocket支持

/**
 * 開啓websocket的支持
 */
@Configuration
public class WebSocketConfig {
    @Bean
    public ServerEndpointExporter serverEndpointExporter(){
        return new ServerEndpointExporter();
    }
}

3. 編寫websocket服務類，由於websocket使用的是ws協議，需要使用@ServerEndpoint註解配置請求路徑

@ServerEndpoint(value = "/websocket")
@Component
public class WebSocketServer {

    // 統計在線人數
    private static int onlineCount = 0;

    // 用本地線程保存session
    private static ThreadLocal<Session> sessions = new ThreadLocal<Session>();

    // 保存所有連接上的session
    private static Map<String, Session> sessionMap = new ConcurrentHashMap<String, Session>();

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

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

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

    // 連接
    @OnOpen
    public void onOpen(Session session) {
        sessions.set(session);
        addOnlineCount();
        sessionMap.put(session.getId(), session);
        System.out.println("【" + session.getId() + "】連接上服務器======當前在線人數【" + getOnlineCount() + "】");
    }

    // 關閉連接
    @OnClose
    public void onClose(Session session) {
        subOnlineCount();
        sessionMap.remove(session.getId());
        System.out.println("【" + session.getId() + "】退出了連接======當前在線人數【" + getOnlineCount() + "】");
    }

    // 接收消息 客戶端發送過來的消息
    @OnMessage
    public void onMessage(String message, Session session) {

        //message的格式可以包含sessionid, 格式[SID,內容XXX]：1,內容
        System.out.println("【" + session.getId() + "】客戶端的發送消息======內容【" + message + "】");
        String[] split = message.split(",");
        String sessionId = split[0];
        Session ss = sessionMap.get(sessionId);
        if (ss != null) {
            String msgTo = "【" + session.getId() + "】發送給【您】的消息:\n【" + split[1] + "】";
            String msgMe = "【我】發送消息給【" + ss.getId() + "】:\n" + split[1];
            sendMsg(ss, msgTo);
            sendMsg(session, msgMe);
        } else {
            for (Session s : sessionMap.values()) {
                if (!s.getId().equals(session.getId())) {
                    sendMsg(s, "【" + session.getId() + "】發送給【您】的廣播消息:\n【" + message + "】");
                } else {
                    sendMsg(session, "【我】發送廣播消息給大家\n" + message);
                }
            }
        }
    }

// 異常

    @OnError
    public void onError(Session session, Throwable throwable) {
        System.out.println("發生異常!");
        throwable.printStackTrace();
    }

    // 發送消息到指定用戶的方法
    public synchronized void sendMsg(Session session, String msg) {
        try {
            session.getBasicRemote().sendText(msg);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    //廣播發送消息
    public synchronized void sendMsgToAll(String msg) {
        try {
            for (Session s : sessionMap.values()) {
                s.getBasicRemote().sendText(msg);
                System.out.println(msg);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

4. 編寫Controller類在方法裏調用WebSocketServer的實例方法實現主動推送

@Controller
public class IndexController {
  @Autowired
    private WebSocketServer webSocketServer;
    
    @RequestMapping("/send.do")
    public ModelAndView send(){
        ModelAndView modelAndView = new ModelAndView("/send.html");
        webSocketServer.sendMsgToAll(“Hello World”);
        return modelAndView;
    }
}

5. 前端js創建websocket連接

		 //判斷當前瀏覽器是否支持WebSocket
        if('WebSocket' in window){
            websocket = new WebSocket("ws://127.0.0.1:8080/websocket");
        }
        else{
            alert('Not support websocket')
        }

        //連接發生錯誤的回調方法
        websocket.onerror = function(){
            setMessageInnerHTML("error");
        };

        //連接成功建立的回調方法
        websocket.onopen = function(event){
            setMessageInnerHTML("open");
        }



        //接收到消息的回調方法
        websocket.onmessage = function(event){
            setMessageInnerHTML(event.data);
        }



        //連接關閉的回調方法
        websocket.onclose = function(){
            setMessageInnerHTML("close");
        }



        //監聽窗口關閉事件，當窗口關閉時，主動去關閉websocket連接，防止連接還沒斷開就關閉窗口，server端會拋異常。
        window.onbeforeunload = function(){
            websocket.close();
        }



        //將消息顯示在網頁上
        function setMessageInnerHTML(innerHTML){
            document.getElementById('message').innerHTML += innerHTML + '<br/>';
        }



        //關閉連接
        function closeWebSocket(){
            websocket.close();
        }

        //發送消息
        function send(){
            var message = document.getElementById('text').value;
            websocket.send(message);
        }