When trying to export on WebLogic 11g, it throws NoClassDefFound exception. I checked the application WAR and jasperreports-3.7.4.jar is included in WEB-INF/lib folder. What
I had the same issue and it was resolved by reducing the /tmp space. It was 100% (/tmp folder). I reduced it to 86% and restarted the server and the noclassdefinitionerror was gone and issue was resolved.