一旦服务器宕机，这段代码就一直在重复调用服务器，该如何停止？

Question

一旦服务器宕机，这段代码就一直在重复调用服务器，一旦请求失败，我如何让它停止重复调用呢？也许是一个catch/error块？但我不确定如何实现它。谢谢!

HttpURLConnection httpConn = null;
InputStream is = null;
OutputStream os = null;
String xmlResponse = null;

try {
   //Open Connection

       String CollectionId="123";
       String GetHTML="1";

       String urlString = "http://tester.com/webservices/ContentWS.asmx/GetCollection?CollectionId="+CollectionId+"&GetHTML="+GetHTML;

       System.out.println(urlString);

       //String encodedUrl = URLEncoder.encode(urlString,"UTF-8");

   URL url = new URL(urlString);
   httpConn = (HttpURLConnection)url.openConnection();

   //Setup Request
   httpConn.setRequestMethod("GET");
   httpConn.setDoOutput(true);
   httpConn.setReadTimeout(10000);
   httpConn.connect();

   xmlResponse = convertStreamToString(httpConn.getInputStream());
  }
  catch (IOException e) {
      e.printStackTrace();
   }

String htmlContent = "";
   try {
       DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
       DocumentBuilder db = dbf.newDocumentBuilder();
       InputSource input = new InputSource();
       input.setCharacterStream(new StringReader(xmlResponse));

       Document doc = db.parse(input);
       NodeList nodes = doc.getElementsByTagName("Item");

       // iterate the Items
               int i = 0;
               int j = 0;
               Date now = new Date();
       for (i = 0; i < 2; i++) {
                  //Grab HTML to append to htmlContent
                  NodeList teaser = doc.getElementsByTagName("Html");
                  Element line = (Element) teaser.item(i);
                  htmlContent += getCharacterDataFromElement(line);
       }
   }
   catch (Exception e) {
       e.printStackTrace();
   }
htmlContent = ...

Answer 1

这段代码打印堆栈跟踪，但不抛出错误，因此您的调用代码不知道这个问题。

让catch()代码块重新抛出错误是否有帮助？

e.printStackTrace();
throw e;

Answer 2

一切似乎都很好用。您的连接已打开并正常工作，但您忘记了一个小细节。完成后，您必须使用HttpURLConnection.disconnect()来告诉程序您已经完成了从连接请求信息。

我从Java的角度看待网络是这样的:建立连接-->发送连接请求-->连接-->获取数据-->对数据做一些事情-->关闭连接

就HttpURLConnection.disconnect()而言，需要注意的是，即使抛出异常，它也会断开连接。如果愿意，您可以尝试在末尾添加} finally {语句。