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(Quick Reference) # 7.4.2 Mapping to REST resources - Reference Documentation Authors: Graeme Rocher, Peter Ledbrook, Marc Palmer, Jeff Brown, Luke Daley, Burt Beckwith, Lari Hotari Version: 2.3.8 ## 7.4.2 Mapping to REST resources Since Grails 2.3, it possible to create RESTful URL mappings that map onto controllers by convention. The syntax to do so is as follows:
    "/books"(resources:'book')
You define a base URI and the name of the controller to map to using the `resources` parameter. The above mapping will result in the following URLs:
HTTP Method | URI | Grails Action
--- | --- | ---
GET | /books | index
GET | /books/create | create
POST | /books | save
GET | /books/${id} | show
GET | /books/${id}/edit | edit
PUT | /books/${id} | update
DELETE | /books/${id} | delete
If you wish to include or exclude any of the generated URL mappings you can do so with the `includes` or `excludes` parameter, which accepts the name of the Grails action to include or exclude:

    "/books"(resources:'book', excludes:['delete', 'update'])or"/books"(resources:'book', includes:['index', 'show'])
#### Single resources A single resource is a resource for which there is only one (possibly per user) in the system. You can create a single resource using the `resource` parameter (as oppose to `resources`):
    "/book"(resource:'book')
This results in the following URL mappings:
HTTP Method | URI | Grails Action
--- | --- | ---
GET | /book/create | create
POST | /book | save
GET | /book | show
GET | /book/edit | edit
PUT | /book | update
DELETE | /book | delete
The main difference is that the id is not included in the URL mapping. #### Nested Resources You can nest resource mappings to generate child resources. For example:
    "/books"(resources:'book') {
      "/authors"(resources:"author")
    }
The above will result in the following URL mappings:
HTTP Method | URL | Grails Action
--- | --- | ---
GET | /books/${bookId}/authors | index
GET | /books/${bookId}/authors/create | create
POST | /books/${bookId}/authors | save
GET | /books/${bookId}/authors/${id} | show
GET | /books/${bookId}/authors/edit/${id} | edit
PUT | /books/${bookId}/authors/${id} | update
DELETE | /books/${bookId}/authors/${id} | delete
You can also nest regular URL mappings within a resource mapping:
    "/books"(resources: "book") {
        "/publisher"(controller:"publisher")
    }
This will result in the following URL being available:
HTTP Method | URL | Grails Action
--- | --- | ---
GET | /books/1/publisher | index
#### Linking to RESTful Mappings You can link to any URL mapping created with the `g:link` tag provided by Grails simply by referencing the controller and action to link to:
    <g:link controller="book" action="index">My Link</g:link>
As a convenience you can also pass a domain instance to the `resource` attribute of the `link` tag:
    <g:link resource="${book}">My Link</g:link>
This will automatically produce the correct link (in this case "/books/1" for an id of "1"). The case of nested resources is a little different as they typically required two identifiers (the id of the resource and the one it is nested within). For example given the nested resources:
    "/books"(resources:'book') {
      "/authors"(resources:"author")
    }
If you wished to link to the `show` action of the `author` controller, you would write:
    // Results in /books/1/authors/2
    <g:link controller="author" action="show" method="GET" params="[bookId:1]" id="2">The Author</g:link>
However, to make this more concise there is a `resource` attribute to the link tag which can be used instead:
    // Results in /books/1/authors/2
    <g:link resource="book/author" action="show" bookId="1" id="2">My Link</g:link>
The resource attribute accepts a path to the resource separated by a slash (in this case "book/author"). The attributes of the tag can be used to specify the necessary `bookId` parameter. | Quick Reference (hide)