java - 为什么我收到此错误文件过早结束？

Question

我正在尝试解析 XML 响应，但失败得很惨。我一开始以为xml 只是没有在响应中返回，所以我制作了下面的代码，并直接链接到我的 xml 文件在线。我能够毫无问题地将 XML 打印到屏幕上。但是，当我调用我的解析方法时，我得到 Premature end of file.

如果我直接传递 URL 就可以了:

• builder.parse("");

但是当我通过 InputStream 时失败:

• builder.parse(connection.getInputStream());

    try {
      URL url = new URL(xml);
      URLConnection uc =  url.openConnection();
      HttpURLConnection  connection = (HttpURLConnection )uc;
  
      connection.setDoInput(true);
      connection.setDoOutput(true);
  
      InputStream instream;
      InputSource source;
      //get XML from InputStream
      if(connection.getResponseCode()>= 200){
          connection.connect();       
          instream = connection.getInputStream();         
          parseDoc(instream);     
      }
      else{
          instream = connection.getErrorStream();
      }
  
  
  } catch (MalformedURLException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
  } catch (IOException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
  } catch (ParserConfigurationException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
  } catch (SAXException e) {
      // TODO Auto-generated catch block
      e.printStackTrace();
  }
  
  
  
   static void parseDoc(InputStream instream) throws ParserConfigurationException,
   SAXException, IOException{
  
  
    BufferedReader buff_read = new BufferedReader(new InputStreamReader(instream,"UTF-8"));
      String  inputLine = null;
  
      while((inputLine = buff_read.readLine())!= null){
          System.out.println(inputLine);
      }
  
    DocumentBuilderFactory factory =DocumentBuilderFactory.newInstance();
    factory.isIgnoringElementContentWhitespace();
    DocumentBuilder builder = factory.newDocumentBuilder();
    Document doc = builder.parse(instream);
  }
  

我得到的错误:

    [Fatal Error] :1:1: Premature end of file.
org.xml.sax.SAXParseException: Premature end of file.
    at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(Unknown Source)
    at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(Unknown Source)
    at javax.xml.parsers.DocumentBuilder.parse(Unknown Source)
    at com.ameba.api.network.MainApp.parseDoc(MainApp.java:78)
    at com.ameba.api.network.MainApp.main(MainApp.java:41)

Answer 1

当你这样做时，

while((inputLine = buff_read.readLine())!= null){
        System.out.println(inputLine);
    }

您在流内消耗所有内容，因此流内是空的。现在尝试这样做时，

Document doc = builder.parse(instream);

解析将失败，因为您传递了一个空流。