How to separate interface from implementation in Grails services?

Question

I was wondering if it\'s possible to create a service interface on Grails and I can\'t find a proper way of doing it. This explanation isn\'t satisfactory, since it seems to mix

Answer 1

You can have an interface, but actually you don't need one. If I understand you correctly you would like to have two implementations of a service and be able to choose which one to use.

Simply implement two services named for example MyService1 and MyService2, then in grails-app/conf/spring/resource.groovy you can specify:

beans = {
    ... 
    // syntax is beanId(implementingClassName) { properties }
    myService(MyService1)
    ...
}

or even:

beans = {
    ...
    if (someConfigurationOption) {
        myService(MyService1)
    } else {
        myService(MyService2)
    }
}

This is how you tell Spring which service to actually inject for myService. Now you will be able to use myService like:

public MyController {
    def myService
    ...
}

and Spring will auto wire a proper implementation. This allows you to configure which service implementation to use based for example on some configuration.