I have helped somebody troubleshoot an issue with my JasperReportsIntegration kit. Although he had followed the instructions correctly, the report wouldn't show in the application.
It worked correctly when calling the j2ee application in the tomcat directly, but not when calling the report using the plsql interface xlib_jasperreports (which calls the j2ee server using utl_http)
The issue is related to the XML DB listener (also the primary http listener of Oracle XE) not supporting the http 1.1 standard. Since the XML DB listener only supports the 1.0 standard, the http parameter chunked transfer encoding is not working properly.
When calling the report through my JasperReportsIntegration toolkit you would either see an empty report or nothing at all.
See this thread for more details and your options: http://forums.oracle.com/forums/thread.jspa?messageID=4563910#4563910
Also, this problem will not crop up when you use a plain Apache as a proxy to your XE installation.