Grails Generate Asynchronous Controller

Since version 2.3, Grails supports asynchronous parallel programming to support modern multiple core hardware. Therefore a new Grails command is added to generate asynchronous controllers for domain classes. The generated controller contains CRUD actions for a given domain class. In the example below, we will generate a default asynchronous implementation of a Grails controller.

First we create a domain object:

 $ grails create-domain-class grails.data.Movie

Second we will generate the asynchronous controller using the new generate-async-controller command:

 $ grails generate-async-controller grails.data.Movie

Grails now generates an asynchronous controller with the name MovieController. Below you can see the default implementation of the index method:

def index(Integer max) {

       params.max = Math.min(max ?: 10, 100)
       Movie.async.task {
           [movieInstanceList: list(params), count: count() ]
       }.then { result ->
           respond result.movieInstanceList, model:[movieInstanceCount: result.count]
       }
}

The async namespace makes sure GORM methods in the task method will be performed in a different thread and therefore is asynchronous. The task method which is used, returns a Promises object which you can use to perform callback operations like onError and onComplete.