To Create a Listener, create a directory structure to match below <jira-home>/data/scripts, like:

cd /opt/jira-data/data/script
mkdir com com/firm com/firm/listener

go to the directory and make a class file:

package com.firm.listener

import com.atlassian.jira.event.issue.AbstractIssueEventListener
import com.atlassian.jira.event.issue.IssueEvent

class ExampleListener extends AbstractIssueEventListener {
    @Override
    void workflowEvent(IssueEvent event) {

        System.out.println("Add a text to the catalina.out")
    }

}

 

Add the class file to JIRA:

Reference: https://jamieechlin.atlassian.net/wiki/display/GRV/Listeners#Listeners-CustomGroovyListeners%28foradvancedusers%29