This is an german article about: How to write a Servlet which produces realtime thumbnails from BIRT Reports.
In this approach the JSF4Birt Library is used to get a shared BIRT runtime inside a webapplication. This BIRT runtime instance is then used to rund and render a given report to a pdf. After this the application gets an image from the first page of the report, which is then send to the client as a servlet response.
You can find the full article her: http://developer-services.net/?p=70