Grails Controller namespaces

Grails 2.3 introduced controller namespaces. This feature gives Grails developers the option to have multiple controllers that use the same name (within different packages).

It is not that hard to get into a situation where you want two or more controllers with the same name.
Assume we have an application that gives users the option to update their personal profile settings. We might have a ProfileController for this. Now we might also need an administration backend which gives administrators the option to update user profiles. ProfileController would again be a good name for handling these kinds of requests.

With Grails 2.3 we can now do this by adding namespaces to controllers using the static namespace property:

package foo.bar.user

class ProfileController {

  static namespace = 'user'

  // actions that can be accessed by users
}

package foo.bar.admin

class ProfileController {

  static namespace = 'admin'

  // actions that can be accessed by administrators
}

We can now use the namespace to map the controllers to different URLs within UrlMappings.groovy:

class UrlMappings {

  static mappings = { 
    '/profile' { 
      controller = 'profile' 
      namespace = 'user' 
    }
    '/admin/profile' { 
      controller = 'profile' 
      namespace = 'admin' 
    }
    ..
  }
}

To make the namespace part of the URL by default we can use the $namespace variable:

static mappings = { 
  "/$namespace/$controller/$action?"() 
}

Using this way we are able to access our controllers with the following URLs:

/user/profile/<action>
/admin/profile/<action>

Please note that we also need to provide the namespace when building links:

<g:link controller="profile" namespace="admin">Profile admin functions</g:link>