OK, created a custom expression function, and I have a test version of JasperReports Server 5.2. I copied my jar file to /usr/local/tomcat/webapps/ROOT/WEB-INF/lib and all is good.
Now to move to production, we have JasperReports Pro server 5.1 -I copied my jar file to the same location on prod, but now my custom expressions cannot be resolved -is there another place I should be copying my custom expresssion jar to? Or does (gulp) 5.1 not support custom expressions?
Did you also remember to update your WEB_INF\applicationContext-adhoc.xml and \WEB_INF\bundles\ adhoc_messages.properties files? It seems like it should work on 5.1, since these instructions have been in place since 3.5, and I haven't heard of 5.1 specific-bugs around this.
In addition, you need to restart the server to get it to see the jars. You might verify on a test 5.1 instance before you play too much with prod.