Answer by mdoar for How to set the description of a JIRA Workflow Validator?

I wrote an O'Reilly book Practical Jira Plugins back in 2011 that has a validator example. The source for this is at https://bitbucket.org/mdoar/practical-jira-plugins/src/default/ (and the book is Out There).

But frankly these days I'd use ScriptRunner, JMWE or other plugins that let you write custom workflow things. But don't let that stop you learning it! Good luck