Grails slack plugin appears to do most of the work here
Visit: https://slack.com/ and create a new slack channel Goto Configure apps/integration and create a webhook Configure webhook url in the plugin
If you are using pre grails 2.3, get hold of the grails 2 project from : https://github.com/mathifonseca/grails-slack/tree/grails-2.x
Copy the content of the plugin https://github.com/mathifonseca/grails-slack/tree/grails-2.x/src/groovy/grails/plugin/slack & https://github.com/mathifonseca/grails-slack/tree/master/grails-app/services/grails/plugin/slack to your local application For grails 2.0.1: