Gradle Goodness: Create Objects Using DSL With Domain Object Containers

Gradle offers the NamedDomainObjectContainer class to create a collection of objects defined using a clean DSL. The only requirement for the objects we want to create is that they have a constructor that takes a  String argument and a  name property to identify the object. The value for the  name property must be unique within the collection of objects. We create a new instance of a  NamedDomainObjectContainer with the  container method of the Gradle  Project class. We can add the  NamedDomainObjectContainer instance to the  extensions property of our  project , so we can use a DSL to create instances of objects that need to be in the  NamedDomainObjectContainer object in our project.

The following code shows a simple build script in which we want to create a collection of Product objects. The creation of the NamedDomainObjectContainer object is done in a plugin so we only have to apply the plugin to use the DSL to create  Product objects:

apply plugin: ProductsPlugin

// DSL to define new objects of type Product.
products {
    // Create Product with name pencil.
    pencil {
        price = 0.05
    }
    // Create Product with name crayon.
    crayon {
        price = 0.18
    }
}
class ProductsPlugin implements Plugin<Project> {
    void apply(final Project project) {
        // Create NamedDomainObjectContainer instance for
        // a collection of Product objects
        NamedDomainObjectContainer<Product> productContainer =
            project.container(Product)

    // Add the container instance to our project
    // with the name products.
    project.extensions.add('products', productContainer)

    // Simple task to show the Product objects
    // that are created by Gradle using
    // the DSL syntax in our build file.
    project.task('reportProducts') << {
        def products = project.extensions.getByName('products')

        products.all {
            // A Product instance is the delegate
            // for this closure.
            println "$name costs $price"
        }
    }
}

}
class Product {
    // We need a name property
    // so the object can be created
    // by Gradle using a DSL.
    String name

BigDecimal price

Product(final String name) {
    this.name = name
}

}</pre> 
We can run the reportProducts task to see the  name and  price properties of the  Product instances: 

$ gradle -q reportProducts
crayon costs 0.18
pencil costs 0.05
$
 
Written with Gradle 2.11.
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