This is a bug from Jasper Server, the problems is explain in this thread: http://stackoverflow.com/questions/7913457/cannot-compile-webapp-sample-of-jasperreports The solution is here: http://community.jaspersoft.com/questions/824896/how-use-custom-functions-jar-jasperserver-too Other solution is use the .jar in only subreports(use methods and functions), not in the main report.