many files from a server instead of loading one large file like a zip file
There's usually no point in zipping images because they're already compressed. What a lot of big sites do is glue all their images together in a big patchwork blanket and send the 'megaimage' in one go and use positioning and cropping in the browser to re-use the same image over and over, but show different parts in different places. It's not so bad anyway, unless you're distant from the server so that the return-trip from the end of one image to the beginning of the next response is a large fraction of (or even greater than!) the transfer time of the image.
What is your essential problem? Is it that you need to convert a filesystem path for a temporary file to an URL so that you can create files somewhere where your users can request them? There ought to be a simple crude solution and also a cunning one that Tomcat provides. My application server doesn't naturally do HTTP file serving, so I have to explicitly map every servable native file to a client-side URL. You should be able to just kludge it by doing a string replace on the filesystem path prefix of the temporary directory with a valid URL prefix for the same files. If your temporary files are not in a part of your filesystem that's accessible to Tomcat (will it be the Apache DocumentRoot?), then you may have to write some code to manually read bytes from the files and send their content.