Linking external files from Java Web Server

Question

I have a java servlet that upon a request crunches on data and produces an image. There can potentially be millions of images and once produced they don't need to be re-rendered so I'd like to cache them and avoid the render step as it is quite tedious.

I have the cacheing working fine but the problem is I need these rendered images to persist between deployments of my web application, i.e., I can't write them into the docbase or else they get destroyed upon redeployment.

What I've been doing is using the 'allowLinking' attribute of the Context as my web application is deployed as a war file (context is in META-INF/context.xml). This is somewhat tedious because I need to break the symbolic link before my application is undeployed or else the images in the link are destroyed, but it seems to work.

But this only works for Tomcat and when testing with JBoss (5.1) it doesn't seem to honor the symbolic link and doesn't allow linking to anything outside of the docbase. I'm thinking there has to be a more practical way to accomplish this that works for all Java Web Servers. What am I missing?

Answer 1

You could just configure a servlet that would serve the images from an external directory. This servlet would just have to extract the image file name or ID from the request, read the file from an external directory and write the bytes to the servlet response's output stream (with the appropriate content type set on the response).

Or you could add an Apache httpd server front-end which would serve the static images from some external directory, and delegate to your servlet container for the other URLs.