Properties

Open a report in JReport Designer. In the Report Inspector, select the node that represents the report and you will find the three exit function properties: BeforeRun, AfterRun and AfterInitParameter.

BeforeRun
Calls a program developed by yourself just before running a report.
AfterRun
Allows you to call a program developed by yourself after running a report.
AfterInitParameter
When running the report, after you enter parameters in the pop-up parameter dialog, this function allows you to call a program developed by yourself.

Reference: For API information, see JReport Designer Javadoc jet.util package and jet.exception package in <install_root>\help\designer\api.