Content-Length not returned for PDF files

jwpdx

Using XMLHTTPRequest, I am trying to access the content-length reponse header for a .pdf file, however it's not being returned. If I do the same for a .jpg file then content-length is returned, so I at least know that my code is working. Unfortunately, I need it for PDFs specifically.

 

Below is a partial code snippet that I'm using for debugging purposes that returns all header info, so I can see what all IS being returned. Again, for .jpg files I see Content-Length, but not for .pdf files.

 

Any ideas why this would be the case? Is there a way to ensure that content-length is returned for PDFs?

 

  var xhr = new XMLHttpRequest();
  xhr.onreadystatechange = function(){
    if (xhr.readyState === 4) {
      alert(xhr.getAllResponseHeaders());
    }
  };

  xhr.open("HEAD", url, true);
  xhr.send();

 

Thanks

Rick Poulin

Larger documents tend to be "chunked" by the web server, in essence to avoid connection problems during the transfer. Long story short, when this happens, the HTTP spec doesn't allow the server to specify the content length of the full response.

 

In particular, section 4.4 in the HTTP 1.1 spec states:

2.If a Transfer-Encoding header field (section 14.41) is present and has any value other than "identity", then the transfer-length is defined by use of the "chunked" transfer-coding (section 3.6), unless the message is terminated by closing the connection.

3.If a Content-Length header field (section 14.13) is present, its decimal value in OCTETs represents both the entity-length and the transfer-length. The Content-Length header field MUST NOT be sent if these two lengths are different (i.e., if a Transfer-Encoding header field is present). If a message is received with both a Transfer-Encoding header field and a Content-Length header field, the latter MUST be ignored.

 

So whatever it is you're trying to do, you'll have to find another way (e.g. create a Java servlet that checks the file system and returns the size of the target file, maybe).