The export process for pdf and html relies upon images being made available on the local filesystem. When it comes to thumbnails (generated from the original image by a servlet) this is no longer possible - there is no local file system representation of the thumbnail of an image.

Options:

A) for PDF, reference the absolute url for an image (thumbnailed or otherwise) within the fo document. This will allow the system to do whatever processing is required to generate the image. The problem here is authentication. When the pdf generation process sends a request to the server, it needs to be authenticated with the users credentials. Adding the users credentials to the url is not an option as this would leave a trail of username/password entries on the servers access logs. Somehow we need to assume the identity of the current http requests user.

B) write the thumbnails to disk when they are viewed, and then use this 'disk cache' to serve the export process. A complication to this is ensuring that we keep the thumbnails up to date when the original image is changed, deleting the thumbnail when the original image is changed etc etc.

c)?