(Quick Reference) # 8.4.13 Namespaced Controllers Version: 3.2.8 ## 8.4.13 Namespaced Controllers If an application defines multiple controllers with the same name in different packages, the controllers must be defined in a namespace. The way to define a namespace for a controller is to define a static property named `namespace` in the controller and assign a String to the property that represents the namespace. grails-app/controllers/com/app/reporting/AdminController.groovy
    package com.app.reporting

    class AdminController {

        static namespace = 'reports'

        // ...
    }
grails-app/controllers/com/app/security/AdminController.groovy
    package com.app.security

    class AdminController {

        static namespace = 'users'

        // ...
    }
When defining url mappings which should be associated with a namespaced controller, the `namespace` variable needs to be part of the URL mapping. grails-app/controllers/UrlMappings.groovy
    class UrlMappings {

        static mappings = {
            '/userAdmin' {
                controller = 'admin'
                namespace = 'users'
            }

            '/reportAdmin' {
                controller = 'admin'
                namespace = 'reports'
            }

            "/$namespace/$controller/$action?"()
        }
    }
Reverse URL mappings also require that the `namespace` be specified.
    <g:link controller="admin" namespace="reports">Click For Report Admin</g:link>
    <g:link controller="admin" namespace="users">Click For User Admin</g:link>
When resolving a URL mapping (forward or reverse) to a namespaced controller, a mapping will only match if the `namespace` has been provided. If the application provides several controllers with the same name in different packages, at most 1 of them may be defined without a `namespace` property. If there are multiple controllers with the same name that do not define a `namespace` property, the framework will not know how to distinguish between them for forward or reverse mapping resolutions. It is allowed for an application to use a plugin which provides a controller with the same name as a controller provided by the application and for neither of the controllers to define a `namespace` property as long as the controllers are in separate packages. For example, an application may include a controller named `com.accounting.ReportingController` and the application may use a plugin which provides a controller named `com.humanresources.ReportingController`. The only issue with that is the URL mapping for the controller provided by the plugin needs to be explicit in specifying that the mapping applies to the `ReportingController` which is provided by the plugin. See the following example.
    static mappings = {
        "/accountingReports" {
            controller = "reporting"
        }
        "/humanResourceReports" {
            controller = "reporting"
            plugin = "humanResources"
        }
    }
With that mapping in place, a request to `/accountingReports` will be handled by the `ReportingController` which is defined in the application. A request to `/humanResourceReports` will be handled by the `ReportingController` which is provided by the `humanResources` plugin. There could be any number of `ReportingController` controllers provided by any number of plugins but no plugin may provide more than one `ReportingController` even if they are defined in separate packages. Assigning a value to the `plugin` variable in the mapping is only required if there are multiple controllers with the same name available at runtime provided by the application and/or plugins. If the `humanResources` plugin provides a `ReportingController` and there is no other `ReportingController` available at runtime, the following mapping would work.
    static mappings = {
        "/humanResourceReports" {
            controller = "reporting"
        }
    }
It is best practice to be explicit about the fact that the controller is being provided by a plugin. | Quick Reference (hide)