Jasper Reports Grails Plugin - sub-reports

Here's something that tripped me up when developing my first JasperReport containing a sub-report for use with the JasperReport grails plugin. In order for the sub-report to resolve correctly you need to add a parameter to your parent report called SUBREPORT_DIR. This is then set by the JR plugin, and makes everything work as expected. When specifying the sub-report location, set it to

$P{SUBREPORT_DIR}  + "mysubreport.jasper"

(assuming your subreport is in the same directory as the parent report and called mysubreport.jasper) Don't forget to give the parameter a default value of empty string so that it still works when previewing in iReport. You also need to remember that the plugin runs the compiled versions (*.jasper not *.jrxml) so you need to compile the reports with iReport before running the application.

Jasper Reports Grails Plugin Gotcha

Thought I'd blog this quickly: If you're using iReport to develop reports for use with the Jasper Reports grails plugin, make sure you download the version that matches the version of Jasper that the plugin uses (currently 2.0.5). Otherwise you get terribly unhelpful exceptions like:

java.lang.NullPointerException
 at net.sf.jasperreports.engine.JRPropertiesMap.readObject(JRPropertiesMap.java:185)