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      }  }

$ gradle -q reportProducts  crayon costs 0.18  pencil costs 0.05  $