[java] Why am I getting this error Premature end of file?

I am trying to parse an XML response, but I am failing miserably. I thought initially that the xml was just not being returned in the response, so I crafted up the code below with a direct link to my xml file online. I am able to print the XML to screen with no problems. However when I call my parse method I get Premature end of file.

It works if I pass the URL directly:

• builder.parse("");

but fails when I passed an InputStream:

• 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);
  }
  

The errors I am getting:

    [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)

Use inputstream once don't use it multiple times and Do inputstream.close()

I resolved the issue by converting the source feed from http://www.news18.com/rss/politics.xml to https://www.news18.com/rss/politics.xml

with http below code was creating an empty file which was causing the issue down the line

    String feedUrl = "https://www.news18.com/rss/politics.xml"; 
    File feedXmlFile = null;

    try {
    feedXmlFile =new File("C://opinionpoll/newsFeed.xml");
    FileUtils.copyURLToFile(new URL(feedUrl),feedXmlFile);


          DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
          DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
          Document doc = dBuilder.parse(feedXmlFile);

I came across the same error, and could easily find what was the problem by logging the exception:

documentBuilder.setErrorHandler(new ErrorHandler() {
    @Override
    public void warning(SAXParseException exception) throws SAXException {
        log.warn(exception.getMessage());
    }

    @Override
    public void fatalError(SAXParseException exception) throws SAXException {
        log.error("Fatal error ", exception);
    }

    @Override
    public void error(SAXParseException exception) throws SAXException {
        log.error("Exception ", exception);
    }
});

Or, instead of logging the error, you can throw it and catch it where you handle the entries, so you can print the entry itself to get a better indication on the error.

You are getting the error because the SAXBuilder is not intelligent enough to deal with "blank states". So it looks for at least an <xml ..> declaration, and when that causes a no data response it creates the exception you see rather than report the empty state.

One of the other reason is , you should whitelist your IP address (IPv4) in your mongodb settings. Hope it resolves !

For those who reached this post for Answer:

This happens mainly because the InputStream the DOM parser is consuming is empty

So in what I ran across, there might be two situations:

1. The InputStream you passed into the parser has been used and thus emptied.
2. The File or whatever you created the InputStream from may be an empty file or string or whatever. The emptiness might be the reason caused the problem. So you need to check your source of the InputStream.