(Quick Reference)
                Service Usage
A service contains business logic that can be reused across a Grails application. In Grails a service is a class with a name that ends in the convention "Service" and lives in the 
grails-app/services directory. A service can be created with the 
create-service command:
grails create-service org.bookstore.Book
or with your favourite IDE or text editor.
package org.bookstoreclass BookService {
    Book[] getBooks() {
        Book.list() as Book[]
    }
}Refer to the user guide topic on 
Services for more information.