java實現web實時訊息推播的七種方案

setInterval(() => {
  // 方法請求
  messageCount().then((res) => {
      if (res.code === 200) {
          this.messageCount = res.data
      }
  })
}, 1000);

@Controller
@RequestMapping("/polling")
public class PollingController {
    // 存放監聽某個Id的長輪詢集合
    // 執行緒同步結構
    public static Multimap<String, DeferredResult<String>> watchRequests = Multimaps.synchronizedMultimap(HashMultimap.create());
    /**
     * 公眾號：程式設計師小富
     * 設定監聽
     */
    @GetMapping(path = "watch/{id}")
    @ResponseBody
    public DeferredResult<String> watch(@PathVariable String id) {
        // 延遲物件設定超時時間
        DeferredResult<String> deferredResult = new DeferredResult<>(TIME_OUT);
        // 非同步請求完成時移除 key，防止記憶體溢位
        deferredResult.onCompletion(() -> {
            watchRequests.remove(id, deferredResult);
        });
        // 註冊長輪詢請求
        watchRequests.put(id, deferredResult);
        return deferredResult;
    }
    /**
     * 公眾號：程式設計師小富
     * 變更資料
     */
    @GetMapping(path = "publish/{id}")
    @ResponseBody
    public String publish(@PathVariable String id) {
        // 資料變更 取出監聽ID的所有長輪詢請求，並一一響應處理
        if (watchRequests.containsKey(id)) {
            Collection<DeferredResult<String>> deferredResults = watchRequests.get(id);
            for (DeferredResult<String> deferredResult : deferredResults) {
                deferredResult.setResult("我更新了" + new Date());
            }
        }
        return "success";
    }

@ControllerAdvice
public class AsyncRequestTimeoutHandler {
    @ResponseStatus(HttpStatus.NOT_MODIFIED)
    @ResponseBody
    @ExceptionHandler(AsyncRequestTimeoutException.class)
    public String asyncRequestTimeoutHandler(AsyncRequestTimeoutException e) {
        System.out.println("非同步請求超時");
        return "304";
    }
}

<iframe src="/iframe/message" style="display:none"></iframe>

@Controller
@RequestMapping("/iframe")
public class IframeController {
    @GetMapping(path = "message")
    public void message(HttpServletResponse response) throws IOException, InterruptedException {
        while (true) {
            response.setHeader("Pragma", "no-cache");
            response.setDateHeader("Expires", 0);
            response.setHeader("Cache-Control", "no-cache,no-store");
            response.setStatus(HttpServletResponse.SC_OK);
            response.getWriter().print(" <script type="text/javascript">n" +
                    "parent.document.getElementById('clock').innerHTML = "" + count.get() + "";" +
                    "parent.document.getElementById('count').innerHTML = "" + count.get() + "";" +
                    "</script>");
        }
    }
}

<script>
    let source = null;
    let userId = 7777
    if (window.EventSource) {
        // 建立連線
        source = new EventSource('http://localhost:7777/sse/sub/'+userId);
        setMessageInnerHTML("連線使用者=" + userId);
        /**
         * 連線一旦建立，就會觸發open事件
         * 另一種寫法：source.onopen = function (event) {}
         */
        source.addEventListener('open', function (e) {
            setMessageInnerHTML("建立連線。。。");
        }, false);
        /**
         * 使用者端收到伺服器發來的資料
         * 另一種寫法：source.onmessage = function (event) {}
         */
        source.addEventListener('message', function (e) {
            setMessageInnerHTML(e.data);
        });
    } else {
        setMessageInnerHTML("你的瀏覽器不支援SSE");
    }
</script>

private static Map<String, SseEmitter> sseEmitterMap = new ConcurrentHashMap<>();
/**
 * 建立連線
 *
 * @date: 2022/7/12 14:51
 * @auther: 公眾號：程式設計師小富
 */
public static SseEmitter connect(String userId) {
    try {
        // 設定超時時間，0表示不過期。預設30秒
        SseEmitter sseEmitter = new SseEmitter(0L);
        // 註冊回撥
        sseEmitter.onCompletion(completionCallBack(userId));
        sseEmitter.onError(errorCallBack(userId));
        sseEmitter.onTimeout(timeoutCallBack(userId));
        sseEmitterMap.put(userId, sseEmitter);
        count.getAndIncrement();
        return sseEmitter;
    } catch (Exception e) {
        log.info("建立新的sse連線異常，當前使用者：{}", userId);
    }
    return null;
}
/**
 * 給指定使用者傳送訊息
 *
 * @date: 2022/7/12 14:51
 * @auther: 公眾號：程式設計師小富
 */
public static void sendMessage(String userId, String message) {
    if (sseEmitterMap.containsKey(userId)) {
        try {
            sseEmitterMap.get(userId).send(message);
        } catch (IOException e) {
            log.error("使用者[{}]推播異常:{}", userId, e.getMessage());
            removeUser(userId);
        }
    }
}

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

@Component
@Slf4j
@ServerEndpoint("/websocket/{userId}")
public class WebSocketServer {
    //與某個使用者端的連線對談，需要通過它來給使用者端傳送資料
    private Session session;
    private static final CopyOnWriteArraySet<WebSocketServer> webSockets = new CopyOnWriteArraySet<>();
    // 用來存線上連線數
    private static final Map<String, Session> sessionPool = new HashMap<String, Session>();
    /**
     * 公眾號：程式設計師小富
     * 連結成功呼叫的方法
     */
    @OnOpen
    public void onOpen(Session session, @PathParam(value = "userId") String userId) {
        try {
            this.session = session;
            webSockets.add(this);
            sessionPool.put(userId, session);
            log.info("websocket訊息: 有新的連線，總數為:" + webSockets.size());
        } catch (Exception e) {
        }
    }
    /**
     * 公眾號：程式設計師小富
     * 收到使用者端訊息後呼叫的方法
     */
    @OnMessage
    public void onMessage(String message) {
        log.info("websocket訊息: 收到使用者端訊息:" + message);
    }
    /**
     * 公眾號：程式設計師小富
     * 此為單點訊息
     */
    public void sendOneMessage(String userId, String message) {
        Session session = sessionPool.get(userId);
        if (session != null && session.isOpen()) {
            try {
                log.info("websocket消: 單點訊息:" + message);
                session.getAsyncRemote().sendText(message);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

<script>
    var ws = new WebSocket('ws://localhost:7777/webSocket/10086');
    // 獲取連線狀態
    console.log('ws連線狀態：' + ws.readyState);
    //監聽是否連線成功
    ws.onopen = function () {
        console.log('ws連線狀態：' + ws.readyState);
        //連線成功則傳送一個資料
        ws.send('test1');
    }
    // 接聽伺服器發回的資訊並處理展示
    ws.onmessage = function (data) {
        console.log('接收到來自伺服器的訊息：');
        console.log(data);
        //完成通訊後關閉WebSocket連線
        ws.close();
    }
    // 監聽連線關閉事件
    ws.onclose = function () {
        // 監聽整個過程中websocket的狀態
        console.log('ws連線狀態：' + ws.readyState);
    }
    // 監聽並處理error事件
    ws.onerror = function (error) {
        console.log(error);
    }
    function sendMessage() {
        var content = $("#message").val();
        $.ajax({
            url: '/socket/publish?userId=10086&message=' + content,
            type: 'GET',
            data: { "id": "7777", "content": content },
            success: function (data) {
                console.log(data)
            }
        })
    }
</script>