SpringBoot通知機制的實現(xiàn)方式

更新時間：2021年07月26日 10:04:08 作者：Bupt_Lili

這篇文章主要介紹了SpringBoot通知機制的實現(xiàn)方式，具有很好的參考價值，希望對大家有所幫助。如有錯誤或未考慮完全的地方，望不吝賜教

1. 快速創(chuàng)建maven管理的SpringBoot項目

1、訪問 http://start.spring.io/

2、選擇構建工具Maven Project、

Spring Boot版本1.3.6以及一些工程基本信息點擊“Switch to the full version.”java版本選擇1.7；

3、點擊Generate Project下載項目壓縮包

4、解壓后

使用eclipse，Import -> Existing Maven Projects -> Next ->選擇解壓后的文件夾-> Finsh，OK done!

使用IDEA的話，按如下步驟導入項目： File -> New -> Project fron Existing Sourses -> 選擇解壓后的直接包含pom.xml文件的demo文件夾，OK -> 選第二項Import project from external model, 選maven，Next -> Next -> 勾選左下角Open Project Structure after import, Next -> Next -> Finish -> 選Yes -> OK -> 大功告成！

（記錄自己踩過的坑：一定要選直接包含pom.xml的demo文件夾，一開始選擇直接解壓后的demo文件夾，結果找不到可以導入的maven項目。）

5、運行剛導入的項目

訪問localhost:8080/hello, 看到頁面顯示Hello World。

6、在這個demo的基礎上進行開發(fā)

2. 通知機制的流程

1、客戶端向server訂閱通知

訂閱信息包括通知類型（notificationTypes）、過濾條件（filteringCriteria）、訂閱者地址（subscriberUri）和 managerId。

請求數(shù)據(jù)以json格式發(fā)送，因此在服務端用@RequestBody Map request 來處理請求中的json數(shù)據(jù)，創(chuàng)建JSONObject 對象，從而根據(jù)參數(shù)名獲取請求中傳入的參數(shù)值。

服務端代碼如下：

@RequestMapping("/notifications")
    public void subscribeNotification(@RequestBody Map request, HttpServletResponse response)
            throws ServletException, IOException, JSONException {

        System.out.println("Enter localhost:8083/notifications. " );

        JSONObject jsonObject = new JSONObject(request);  
        String subscriptionId = (String) jsonObject.get("subscriptionId");  // 通過JSONObject 對象獲取請求中傳入的參數(shù)值
        String notificationType = (String) jsonObject.get("notificationType");
        String filteringCriteria = (String) jsonObject.get("filteringCriteria");
        String managerId = (String) jsonObject.get("managerId");

        System.out.println("subscriptionId=" + subscriptionId + ", notificationType=" + notificationType + ", filteringCriteria=" + filteringCriteria + ", managerId=" + managerId );

        //  some code...   省略了存數(shù)據(jù)庫的操作

        response.setHeader("Location", "http://localhost:8083/notifications/0101");  // 通過response.setHeader()方法設置響應頭
        PrintWriter out = response.getWriter();
        String result = "Success to Subscribe a notification! ";
        out.write(result);
    }

服務端端口設為8083，默認是8080，可以通過在resources 下的application.properties文件里加一條語句server.port=8083 修改為其他端口號。

Postman的接口測試結果如下：

2、服務端將通知發(fā)送給客戶端

請求信息包括訂閱Id(subscriptionId)、通知類型（NotificationType）、發(fā)送者Id(producerId)、消息（message）。首先根據(jù)subscriptionId 從數(shù)據(jù)庫查找到該訂閱的通知類型、過濾條件和訂閱者地址，然后判斷該通知是否符合訂閱條件，符合則將該通知發(fā)送給訂閱者。

服務端代碼如下：

@RequestMapping("/sendNotification")
    public void sendNotification(@RequestBody Map request, HttpServletResponse response)
            throws ServletException, IOException, JSONException {

        System.out.println("request:" + request);

        JSONObject jsonObject = new JSONObject(request);
        System.out.println("jsonObject:" + jsonObject);
        String subscriptionId = (String) jsonObject.get("subscriptionId");
        String notificationType = (String) jsonObject.get("notificationType");
        String producerId = (String) jsonObject.get("producerId");
        String alarmType = (String) jsonObject.getJSONObject("message").get("alarmType");
        System.out.println("subscriptionId=" + subscriptionId + ", notificationType=" + notificationType + ", producerId=" + producerId + ", alarmType=" + alarmType );

        //  some code...  查詢數(shù)據(jù)庫（省略）

        // 模擬數(shù)據(jù)庫查詢結果
        String getNotificationType = "";
        String getAlarmType = "";
        String getsubscriberUri = "";
        if(subscriptionId.equals("http://localhost:8081/notifications/0101")){
            getNotificationType = "alarm";
            getAlarmType = "01";
            getsubscriberUri = "http://localhost:8081/notifications/001";
        }
        if(subscriptionId.equals("http://localhost:8081/notifications/0102")){
            getNotificationType = "alarm";
            getAlarmType = "02";
            getsubscriberUri = "http://localhost:8082/notifications/001";
        }

        // 判斷該通知是否符合訂閱條件
        String subscribeURL = "";
        if(notificationType.equals(getNotificationType) && alarmType.equals(getAlarmType)){
            subscribeURL = getsubscriberUri;
        } else return;

        // 建立連接，將通知發(fā)送給訂閱者
        HttpURLConnection subscribeConnection = null;
        StringBuffer responseBuffer = new StringBuffer();
        try{
            URL getsubscribeURL = new URL(subscribeURL);
            subscribeConnection = (HttpURLConnection) getsubscribeURL.openConnection();  // 建立連接
            subscribeConnection.setDoOutput(true);
            subscribeConnection.setDoInput(true);
            subscribeConnection.setRequestMethod("POST");
            subscribeConnection.setRequestProperty("Accept-Charset", "utf-8");
            subscribeConnection.setRequestProperty("Content-Type", "application/json");
            subscribeConnection.setRequestProperty("Charset", "UTF-8");
            byte[] data = (jsonObject.toString()).getBytes();
            subscribeConnection.setRequestProperty("Content-Length", String.valueOf(data.length));

            // 開始連接請求
            subscribeConnection.connect();
            OutputStream out = subscribeConnection.getOutputStream();
            // 寫入請求的字符串
            out.write((jsonObject.toString()).getBytes());  // 發(fā)送json數(shù)據(jù)
            out.flush();
            out.close();
        }catch (IOException e) {
        }
        if (subscribeConnection.getResponseCode() == 200) {    // 若響應碼為200，則通知訂閱成功
            System.out.println("Success to send the notification." );
            String readLine;
            BufferedReader responseReader = new BufferedReader(new InputStreamReader(
                    subscribeConnection.getInputStream(), "utf-8"));
            while ((readLine = responseReader.readLine()) != null) {
                responseBuffer.append(readLine);
            }
            System.out.println("Http Response:" + responseBuffer);
            subscribeConnection.disconnect();

            PrintWriter out = response.getWriter();
            out.write(responseBuffer.toString());
        }else return;
    }

訂閱者(8081端口)接收通知，代碼如下：

@RequestMapping("/notifications/001")
    public void receiveNotification(@RequestBody Map request, HttpServletResponse response)
            throws ServletException, IOException{
        System.out.println("Receive a new notification." );
        System.out.println("request:" + request);

        PrintWriter out = response.getWriter();
        String result = "Success to Subscribe a notification! ";
        out.write(result);
    }