8.1.1 Understanding Controllers and Actions

Creating a controller

Controllers can be created with the create-controller or generate-controller command. For example try running the following command from the root of a Grails project:

grails create-controller book

The command will create a controller at the location grails-app/controllers/myapp/BookController.groovy:

package myapp
class BookController {
    def index() { }
}

where "myapp" will be the name of your application, the default package name if one isn’t specified.

BookController by default maps to the /book URI (relative to your application root).

Creating Actions

A controller can have multiple public action methods; each one maps to a URI:

class BookController {
    def list() {
        // do controller logic
        // create model
        return model
    }
}

This example maps to the /book/list URI by default thanks to the property being named list.

The Default Action

A controller has the concept of a default URI that maps to the root URI of the controller, for example /book for BookController. The action that is called when the default URI is requested is dictated by the following rules:

• If there is only one action, it’s the default

• If you have an action named index, it’s the default

• Alternatively you can set it explicitly with the defaultAction property:

static defaultAction = "list"