Popular Java Report Generating Tool
JasperReports is a powerful open source Java reporting tool that has the ability to deliver rich content onto the screen, to the printer or into PDF, HTML, XLS, CSV and XML files.
It is entirely written in Java and can be used in a variety of Java enabled applications, including J2EE or Web applications, to generate dynamic content.
Its main purpose is to help creating page oriented, ready to print documents in a simple and flexible manner.
JasperReport Home : http://jasperforge.org/sf/projects/jasperreports