A typical usage pattern in Grails is to inject services into various parts of the app, e.g. : 

class SomeController {
   def someService


}

In many cases, the injected service would not have a static type; however, grails follows a naming convention to avoid having to declare each service. In the example above, hovering over 'someService' should turn into a hyperlink and on clicking on the link should open the SomeService class.