serving files through SSL 2007-11-07 - By Roger Parkinson
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I am trying to deliver some PDFs to the browser using my tomcat
application. It works, but not always under SSL and IE.
One file is a static PDF and it lives inside my war file. That works
just fine. The file is accessed using a url like /myapp/web/myfile.pdf
and that always delivers the file.
Other files are generated by the app and live in a configured directory.
They are delivered through a servlet that looks like this:
String mimeType = sc.getMimeType(filename);
FileHelper helper = new FileHelper();
InputStream in = helper.fetch(filename, m_dir);
response.setContentType(mimeType);
response.setContentLength(10115);
response.addHeader("ETag","W/\"963288-1194247031062");
OutputStream out = response.getOutputStream();
byte[] buf = new byte[1024];
int count = 0;
while ((count = in.read(buf)) >= 0)
{
out.write(buf, 0, count);
}
in.close();
out.close();
So apart from some minor fiddling with the contentType etc I don't do
very much. This works fine outside of SSL and it also works fine with
SSL and Firefox, but not SSL+IE.
Thinking it was a problem with headers I did some research and found a
lot of stuff about setting no cache etc. Tried it and it nothing made
any difference (except that I managed to break it). I have taken all
those out because the static file, the one I mentioned at first, is
delivering okay to IE over SSL so I don't believe there is a problem at
the IE end, or not one that cannot be overcome by getting my response
right at the server end.
I used TCPMonitor to sniff the headers using non-SSL and found that the
static file has this response:
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
ETag: W/"963288-1194247031062"
Last-Modified: Mon, 05 Nov 2007 07:17:11 GMT
Content-Type: application/pdf
Content-Length: 963288
Date: Wed, 07 Nov 2007 04:54:39 GMT
... pdf file follows
So there doesn't seem to be too much going on there.
When I respond to the request for the dynamic file it looks like this:
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Pragma: No-cache
Cache-Control: no-cache
Expires: Thu, 01 Jan 1970 12:00:00 NZST
ETag: W/"963288-1194247031062
Content-Type: application/pdf
Content-Length: 10115
Date: Wed, 07 Nov 2007 05:32:02 GMT
...pdf file follows.
I am getting some cache headers added for free otherwise there is no
difference in the request.
Of course those headers may be making all the difference because IE's
message is 'cannot write the file to cache' which is a bit odd because
we've explicitly told it not to here.
Searching the web on this has a number of answers that suggest adding
those no-cache headers anyway.
So, does anyone know what I need to do to make the two responses enough
the same to stop IE complaining?
I am aware that I have faked the ETag and the length of the file and
that I need to do something smarter there, but I'll do that when it
starts working.
Version info: Tomcat 5.5, Java 1.5, WinXP SP2
Thanks for your help.
Roger
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