are there any java-based or j2ee-based reporting tools? I have a large website and some users require printed reports based on the portal data.
I am not sure what your specific requirements are. But you sure can visit www.informatica.com to see whether they have what you want .
You should have a look at https://www.inetsoftware.de/products/crystalclear/.
It is a java-based report tool & designer with a good functionality.
A free trial is available.
JavaToolbox references Java tools and has a category dedicated to reporting tools. See http://javatoolbox.com/categories/reporting
Another reporting solution is Docmosis http://www.docmosis.com. It can produce documents/reports in various formats using templates in various formats optionally within a J2EE container.