Example 17.11. Configuring a task - with configure() method
build.gradle
task myCopy(type: Copy)
myCopy.configure { from('source') into('target')
include('**/*.txt', '**/*.xml', '**/*.properties')
}
Every task has a configure() method, which you can pass a closure for configuring the task. Gradle uses this style for configuring objects in many places, not just for tasks.
You can also use a configuration closure when you define a task.
Example 17.12. Defining a task with closure
build.gradle
task copy(type: Copy) { from 'resources' into 'target'
include('**/*.txt', '**/*.xml', '**/*.properties')
}
17.4. Adding dependencies to a task
There are several ways you can define the dependencies of a task. In Section 6.5, “Tas dependencies” you were introduced to defining dependencies using task names. Task names can refer to tasks in the same project as the task, or to tasks in other projects. To refer to a task in another project, you prefix the name of the task with the path of the project it belongs to. Below is an example which adds a dependency from projectA:taskX to projectB:taskY:
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Example 17.13. Adding dependency on task from another project
build.gradle
project('projectA') {
task taskX(dependsOn: ':projectB:taskY') << { println 'taskX'
}
}
project('projectB') { task taskY << {
println 'taskY'
}
}
Output of gradle -q taskX
> gradle -q taskX taskY
taskX
Instead of using a task name, you can define a dependency using a Task object, as shown in this example:
Example 17.14. Adding dependency using task object
build.gradle
task taskX << { println 'taskX'
}
task taskY << { println 'taskY'
}
taskX.dependsOn taskY
Output of gradle -q taskX
> gradle -q taskX taskY
taskX
For more advanced uses, you can define a task dependency using a closure. When evaluated, the closure is passed the task whose dependencies are being calculated. The closure should return a single Task or collection of Task objects, which are then treated as dependencies of the task. The following example adds a dependency from taskX to all the tasks in the project whose name starts with lib:
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Example 17.15. Adding dependency using closure
build.gradle
task taskX << { println 'taskX'
}
taskX.dependsOn {
tasks.findAll { task -> task.name.startsWith('lib') }
}
task lib1 << { println 'lib1'
}
task lib2 << { println 'lib2'
}
task notALib << { println 'notALib'
}
Output of gradle -q taskX
> gradle -q taskX lib1
lib2 taskX
For more information about task dependencies, see the Task API.
17.5. Adding a description to a task
You can add a description to your task. This description is for example displayed when executing g
.
Example 17.16. Adding a description to a task
build.gradle
task copy(type: Copy) {
description = 'Copies the resource directory to the target directory.' from 'resources'
into 'target'
include('**/*.txt', '**/*.xml', '**/*.properties')
}
17.6. Replacing tasks
Sometimes you want to replace a task. For example if you want to exchange a task added by the Java plugin with a custom task of a different type. You can achieve this with:
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Example 17.17. Overwriting a task
build.gradle
task copy(type: Copy)
task copy(overwrite: true) << { println('I am the new one.')
}
Output of gradle -q copy
> gradle -q copy I am the new one.
Here we replace a task of type Copy with a simple task. When creating the simple task, you have to set the overwrite property to true. Otherwise Gradle throws an exception, saying that a task with such a name already exists.
17.7. Skipping tasks
Gradle offers multiple ways to skip the execution of a task.
17.7.1. Using a predicate
You can use the onlyIf() method to attach a predicate to a task. The task's actions are onl executed if the predicate evaluates to true. You implement the predicate as a closure. The closure is passed the task as a parameter, and should return true if the task should execute and false if the task should be skipped. The predicate is evaluated just before the task is due to be executed.
Example 17.18. Skipping a task using a predicate
build.gradle
task hello << {
println 'hello world'
}
hello.onlyIf { !project.hasProperty('skipHello') }
Output of gradle hello -PskipHello
> gradle hello -PskipHello :hello SKIPPED
BUILD SUCCESSFUL
Total time: 1 secs
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17.7.2. Using StopExecutionException
If the rules for skipping a task can't be expressed with predicate, you can use the StopExecutionException. If this exception is thrown by an action, the further execution of this action as well as the execution of any following action of this task is skipped. The build continues with executing the next task.
Example 17.19. Skipping tasks with StopExecutionException
build.gradle
task compile << |
{ |
println 'We |
are doing the compile.' |
} |
|
compile.doFirst |
{ |
// Here you |
would put arbitrary conditions in real life. But we use this a |
if (true) { |
throw new StopExecutionException() } |
}
task myTask(dependsOn: 'compile') << { println 'I am not affected'
}
Output of gradle -q myTask
> gradle -q myTask I am not affected
This feature is helpful if you work with tasks provided by Gradle. It allows you to add conditional execution of the built-in actions of such a task. [7]
17.7.3. Enabling and disabling tasks
Every task has also an enabled flag which defaults to true. Setting it to false prevents the execution of any of the task's actions.
Example 17.20. Enabling and disabling tasks
build.gradle
task disableMe << {
println 'This should not be printed if the task is disabled.'
}
disableMe.enabled = false
Output of gradle disableMe
> gradle disableMe :disableMe SKIPPED
BUILD SUCCESSFUL
Total time: 1 secs
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