Grails Goodness: Customize Resource Mappings

Since Grails 2.3 it is very easy to define RESTful URL mappings for a controller. We can use the resources and resource attribute and use a controller name as the value. Grails will then automatically create a couple of URL mappings. Suppose we use the following mapping in grails-app/conf/UrlMappings.groovy: "/api/users"(resources: 'user'), then the following mappings are automatically created:

"/api/users/create"(controller: 'user', action: 'create', method: 'GET')
"/api/users/(*)/edit"(controller: 'user', action: 'edit', method: 'GET')
"/api/users(.(*))?"(controller: 'user', action: 'save', method: 'POST')
"/api/users(.(*))?"(controller: 'user', action: 'index', method: 'GET')
"/api/users/(*)(.(*))?"(controller: 'user', action: 'delete', method: 'DELETE')
"/api/users/(*)(.(*))?"(controller: 'user', action: 'update', method: 'PUT')
"/api/users/(*)(.(*))?"(controller: 'user', action: 'show', method: 'GET')

When we use the resource attribute to define a mapping like "/api/user"(resource: 'user') the following mappings are created by Grails:

"/api/user/create"(controller: 'user', action: 'create', method: 'GET')
"/api/user/edit"(controller: 'user', action: 'edit', method: 'GET')
"/api/user(.(*))?"(controller: 'user', action: 'delete', method: 'DELETE')
"/api/user(.(*))?"(controller: 'user', action: 'update', method: 'PUT')
"/api/user(.(*))?"(controller: 'user', action: 'save', method: 'POST')

Well there a lot of mappings created for us! But maybe we don't need all created mappings in our application. For example the mappings with /create and /edit are created by Grails to support also a UI variant for the controller actions, but we might want to leave them out when we only deal with JSON or XML payloads. We can use the includes and excludes attributes on the mapping to explicitly define which actions we want to support in our controller.

In the following sample UrlMappings.groovy configuration we exclude the create and edit actions in the first mapping. In the second mapping we only include the show and index actions:

// File: grails-app/conf/UrlMappings.groovy
import static org.codehaus.groovy.grails.web.mapping.DefaultUrlMappingEvaluator.*

import org.codehaus.groovy.grails.web.mapping.DefaultUrlMappingEvaluator

class UrlMappings {

    static mappings = {
        // Exclude the 'create' and 'edit' actions for the 
        // automatically created mappings.
        "/api/users"(resources: 'user', excludes: [ACTION_CREATE, ACTION_EDIT])

        // Include only the 'index' and 'show' actions for the 
        // automatically created mappings.
        "/api/products"(resources: 'product', includes: [ACTION_INDEX, ACTION_SHOW])
    }
}

Code written with Grails 2.3.