Question

Given a URL, how can you tell if the referenced file is and html file?

Obviously, its an html file if it ends in .html or /, but then there are .jsp files, too, so I’m wondering what other extensions may be out there for html.

Alternatively, if this information can be easily gained from a URL object in Java, that would be sufficient for my purposes.

Answer 1

Just from the URL you cannot, think of the following urls:

• http://host1/index.html
• http://host2/index.php
• http://host3/index.asp
• http://host4/index.jsp
• http://host5/index.aspx
• Or the the url of this question – How do you determine if a file is html from the URL?

All of them return HTML content. The only sure way is to ask the server for the resource, and check the Content-TYpe header. It is better to use to send an HEAD request to the server, instead of GET or POST – it will give you just the headers and without the content.

  URL url = ...
  HttpURLConnection urlc = (HttpURLConnection)url.openConnection();
  urlc.setAllowUserInteraction( false );
  urlc.setDoInput( true );
  urlc.setDoOutput( false );
  urlc.setUseCaches( true );
  urlc.setRequestMethod("HEAD");
  urlc.connect();
  String mime = urlc.getContentType();
  if(mime.equals("text/html") {
    // do your stuff
  }