Chapter 12. The Project and Task API

In the tutorial in Chapter 4, Build Script Basics we used, for example, the task() method. Where does this method come from? We said earlier that the build script defines a project in Gradle. For Gradle, this means that it creates an instance of Project and associates this Project object with the build script. As the build script executes, it configures this Project object.

Let's try this out and try to access the name property of the Project object.

task check << {
    println name
    println project.name
}

> gradle -q check
projectApi
projectApi

Both println statements print out the same property. The first uses auto-delegation to the Project object, for properties not defined in the build script. The other statement uses the project property available to any build script, which returns the associated Project object. Only if you define a property or a method which has the same name as a member of the Project object, you need to use the project property.

Have a look at the Project API to find out more about project properties and methods.

projectCoreProperties/
  build.gradle
  subProject/
    build.gradle

task check << {
    allprojects {
        println "project path $path"
        println "  project name = $name"
        println "  project dir = '${rootProject.relativePath(projectDir)}'"
        println "  build file = '${rootProject.relativePath(buildFile)}'"
        println "  build dir = '${rootProject.relativePath(buildDir)}'"
    }
}

> gradle -q check
project path :
  project name = projectCoreProperties
  project dir = ''
  build file = 'build.gradle'
  build dir = 'build'
project path :subProject
  project name = subProject
  project dir = 'subProject'
  build file = 'subProject/build.gradle'
  build dir = 'subProject/build'

Many of the methods of the Project instance return task objects. We have already seen some ways that you can use task objects in Chapter 4, Build Script Basics. Look here to learn more about Task .

The project and the task API constitute the core layer of Gradle and provide all the possible interaction options with this layer. ^[8] This core-layer constitutes a language for dependency based programming. ^[9] There are many other projects providing such a language. There is Ant for Java, Rake and Rant for Ruby, SCons for Python, the good old Make and many more. ^[10] We think that one thing that makes Gradle special compared to the other tools, is its strong support for applying dependency based programming on multi-project builds. We also think that just Gradle's core layer (together with its integration of the Ant tasks), provides a more convenient build system than Ant's core layer.