# Task

API Documentation: | `Task`

A `Task` represents a single atomic piece of work for a build, such as compiling classes or generating javadoc.

Each task belongs to a `Project`. You can use the various methods on `TaskContainer` to create and lookup task instances. For example, `TaskContainer.create()` creates an empty task with the given name. You can also use the `task` keyword in your build file:

    task myTask
    task myTask { configure closure }
    task myType << { task action }
    task myTask(type: SomeType)
    task myTask(type: SomeType) { configure closure }

Each task has a name, which can be used to refer to the task within its owning project, and a fully qualified path, which is unique across all tasks in all projects. The path is the concatenation of the owning project's path and the task's name. Path elements are separated using the `:` character.

### Task Actions

A `Task` is made up of a sequence of `Action` objects. When the task is executed, each of the actions is executed in turn, by calling `Action.execute()`. You can add actions to a task by calling `Task.doFirst()` or `Task.doLast()`.

Groovy closures can also be used to provide a task action. When the action is executed, the closure is called with the task as parameter. You can add action closures to a task by calling `Task.doFirst()` or `Task.doLast()` or using the left-shift `<<` operator.

There are 2 special exceptions which a task action can throw to abort execution and continue without failing the build. A task action can abort execution of the action and continue to the next action of the task by throwing a `StopActionException`. A task action can abort execution of the task and continue to the next task by throwing a `StopExecutionException`. Using these exceptions allows you to have precondition actions which skip execution of the task, or part of the task, if not true.

### Task Dependencies and Task Ordering

A task may have dependencies on other tasks or might be scheduled to always run after another task. Gradle ensures that all task dependencies and ordering rules are honored when executing tasks, so that the task is executed after all of its dependencies and any "must run after" tasks have been executed.

Dependencies to a task are controlled using `Task.dependsOn()` or `Task.setDependsOn()`, and `Task.mustRunAfter()`, `Task.setMustRunAfter()`, `Task.shouldRunAfter()` and `Task.setShouldRunAfter()` are used to specify ordering between tasks. You can use objects of any of the following types to specify dependencies and ordering:

- A `String`, `CharSequence` or `groovy.lang.GString` task path or name. A relative path is interpreted relative to the task's `Project`. This allows you to refer to tasks in other projects.
- A `Task`.
- A closure. The closure may take a `Task` as parameter. It may return any of the types listed here. Its return value is recursively converted to tasks. A `null` return value is treated as an empty collection.
- A `TaskDependency` object.
- A `Buildable` object.
- A `Iterable`, `Collection`, `Map` or array. May contain any of the types listed here. The elements of the iterable/collection/map/array are recursively converted to tasks.
- A `Callable`. The `call()` method may return any of the types listed here. Its return value is recursively converted to tasks. A `null` return value is treated as an empty collection.
- An `Object`. The object's `toString()` method is interpreted as a task path or name. The support for custom Objects has been deprecated and will be removed in the next version of Gradle.

### Using a Task in a Build File

#### Dynamic Properties

A `Task` has 4 'scopes' for properties. You can access these properties by name from the build file or by calling the `Task.property()` method. You can change the value of these properties by calling the `Task.setProperty()` method.

- The `Task` object itself. This includes any property getters and setters declared by the `Task` implementation class. The properties of this scope are readable or writable based on the presence of the corresponding getter and setter methods.
- The extensions added to the task by plugins. Each extension is available as a read-only property with the same name as the extension.
- The convention properties added to the task by plugins. A plugin can add properties and methods to a task through the task's `Convention` object. The properties of this scope may be readable or writable, depending on the convention objects.
- The extra properties of the task. Each task object maintains a map of additional properties. These are arbitrary name -> value pairs which you can use to dynamically add properties to a task object. Once defined, the properties of this scope are readable and writable.

#### Dynamic Methods

A `Plugin` may add methods to a `Task` using its `Convention` object.

#### Parallel Execution

By default, tasks are not executed in parallel. Parallel execution can be enabled by the `--parallel` flag when the build is initiated. In parallel mode, the tasks of different projects (i.e. in a multi project build) are able to be executed in parallel. If a task is annotated with `ParallelizableTask`, it may also be executed in parallel with other tasks of the same project. See `ParallelizableTask` for more details on writing parallelizable tasks.

### Properties

Property | Description
`actions` | The sequence of `Action` objects which will be executed by this task, in the order of execution.
`ant` | The `AntBuilder` for this task. You can use this in your build file to execute ant tasks.
`convention` | The `Convention` object for this task. A `Plugin` can use the convention object to contribute properties and methods to this task.
`dependsOn` | The dependencies of this task.
`description` | The description of this task.
`didWork` | Checks if the task actually did any work. Even if a Task executes, it may determine that it has nothing to do. For example, a compilation task may determine that source files have not changed since the last time a the task was run.
`enabled` | Returns if this task is enabled or not.
`extensions` | The container of extensions.
`finalizedBy` | Incubating Returns tasks that finalize this task.
`group` | The task group which this task belongs to. The task group is used in reports and user interfaces to group related tasks together when presenting a list of tasks to the user.
`inputs` | The inputs of this task.
`logger` | The logger for this task. You can use this in your build file to write log messages.
`logging` | The `LoggingManager` which can be used to control the logging level and standard output/error capture for this task. By default, System.out is redirected to the Gradle logging system at the QUIET log level, and System.err is redirected at the ERROR log level.
`mustRunAfter` | Incubating Returns tasks that this task must run after.
`name` | The name of this task. The name uniquely identifies the task within its `Project`.
`outputs` | The outputs of this task.
`path` | The path of the task, which is a fully qualified name for the task. The path of a task is the path of its `Project` plus the name of the task, separated by `:`.
`project` | The `Project` which this task belongs to.
`state` | The execution state of this task. This provides information about the execution of this task, such as whether it has executed, been skipped, has failed, etc.
`taskDependencies` | Returns a `TaskDependency` which contains all the tasks that this task depends on.
`temporaryDir` | Returns a directory which this task can use to write temporary files to. Each task instance is provided with a separate temporary directory. There are no guarantees that the contents of this directory will be kept beyond the execution of the task.

### Methods

Method | Description
`deleteAllActions()` | Removes all the actions of this task.
`dependsOn(paths)` | Adds the given dependencies to this task. See here for a description of the types of objects which can be used as task dependencies.
`doFirst(action)` | Adds the given closure to the beginning of this task's action list. The closure is passed this task as a parameter when executed.
`doFirst(action)` | Adds the given `Action` to the beginning of this task's action list.
`doLast(action)` | Adds the given closure to the end of this task's action list. The closure is passed this task as a parameter when executed.
`doLast(action)` | Adds the given `Action` to the end of this task's action list.
`finalizedBy(paths)` | Incubating Adds the given finalizer tasks for this task.
`hasProperty(propertyName)` | Determines if this task has the given property. See here for details of the properties which are available for a task.
`leftShift(action)` | Adds the given closure to the end of this task's action list. The closure is passed this task as a parameter when executed. You can call this method from your build script using the << left shift operator.
`mustRunAfter(paths)` | Incubating Specifies that this task must run after all of the supplied tasks.
`onlyIf(onlyIfClosure)` | Execute the task only if the given closure returns true. The closure will be evaluated at task execution time, not during configuration. The closure will be passed a single parameter, this task. If the closure returns false, the task will be skipped.
`onlyIf(onlyIfSpec)` | Execute the task only if the given spec is satisfied. The spec will be evaluated at task execution time, not during configuration. If the Spec is not satisfied, the task will be skipped.
`property(propertyName)` | Returns the value of the given property of this task. This method locates a property as follows:
`setProperty(name, value)` | Sets a property of this task. This method searches for a property with the given name in the following locations, and sets the property on the first location where it finds the property.

### Script blocks

No script blocks

### Property details

#### ``List`<`Action`<? super `Task`>>` `actions`

The sequence of `Action` objects which will be executed by this task, in the order of execution.

#### `AntBuilder` `ant` (read-only)

The `AntBuilder` for this task. You can use this in your build file to execute ant tasks.

#### `Convention` `convention` (read-only)

The `Convention` object for this task. A `Plugin` can use the convention object to contribute properties and methods to this task.

#### ``Set`<`Object`>` `dependsOn`

The dependencies of this task.

#### `String` `description`

The description of this task.

#### `boolean` `didWork`

Checks if the task actually did any work. Even if a Task executes, it may determine that it has nothing to do. For example, a compilation task may determine that source files have not changed since the last time a the task was run.

#### `boolean` `enabled`

Returns if this task is enabled or not.

#### `ExtensionContainer` `extensions` (read-only)

The container of extensions.

#### `TaskDependency` `finalizedBy`

Note: This property is incubating and may change in a future version of Gradle.

Returns tasks that finalize this task.

#### `String` `group`

The task group which this task belongs to. The task group is used in reports and user interfaces to group related tasks together when presenting a list of tasks to the user.

#### `TaskInputs` `inputs` (read-only)

The inputs of this task.

#### `Logger` `logger` (read-only)

The logger for this task. You can use this in your build file to write log messages.

#### `LoggingManager` `logging` (read-only)

The `LoggingManager` which can be used to control the logging level and standard output/error capture for this task. By default, System.out is redirected to the Gradle logging system at the QUIET log level, and System.err is redirected at the ERROR log level.

#### `TaskDependency` `mustRunAfter`

Note: This property is incubating and may change in a future version of Gradle.

Returns tasks that this task must run after.

#### `String` `name` (read-only)

The name of this task. The name uniquely identifies the task within its `Project`.

#### `TaskOutputs` `outputs` (read-only)

The outputs of this task.

#### `String` `path` (read-only)

The path of the task, which is a fully qualified name for the task. The path of a task is the path of its `Project` plus the name of the task, separated by `:`.

#### `Project` `project` (read-only)

The `Project` which this task belongs to.

#### `TaskState` `state` (read-only)

The execution state of this task. This provides information about the execution of this task, such as whether it has executed, been skipped, has failed, etc.

#### `TaskDependency` `taskDependencies` (read-only)

Returns a `TaskDependency` which contains all the tasks that this task depends on.

#### `File` `temporaryDir` (read-only)

Returns a directory which this task can use to write temporary files to. Each task instance is provided with a separate temporary directory. There are no guarantees that the contents of this directory will be kept beyond the execution of the task.

### Method details

#### `Task` `deleteAllActions`()

Removes all the actions of this task.

#### `Task` `dependsOn`(``Object`...` paths)

Adds the given dependencies to this task. See here for a description of the types of objects which can be used as task dependencies.

#### `Task` `doFirst`(`Closure` action)

Adds the given closure to the beginning of this task's action list. The closure is passed this task as a parameter when executed.

#### `Task` `doFirst`(``Action`<? super `Task`>` action)

Adds the given `Action` to the beginning of this task's action list.

#### `Task` `doLast`(`Closure` action)

Adds the given closure to the end of this task's action list. The closure is passed this task as a parameter when executed.

#### `Task` `doLast`(``Action`<? super `Task`>` action)

Adds the given `Action` to the end of this task's action list.

#### `Task` `finalizedBy`(``Object`...` paths)

Note: This method is incubating and may change in a future version of Gradle.

Adds the given finalizer tasks for this task.

    task taskY {
        finalizedBy "taskX"
    }

See here for a description of the types of objects which can be used to specify a finalizer task.

#### `boolean` `hasProperty`(`String` propertyName)

Determines if this task has the given property. See here for details of the properties which are available for a task.

#### `Task` `leftShift`(`Closure` action)

Adds the given closure to the end of this task's action list. The closure is passed this task as a parameter when executed. You can call this method from your build script using the << left shift operator.

#### `Task` `mustRunAfter`(``Object`...` paths)

Note: This method is incubating and may change in a future version of Gradle.

Specifies that this task must run after all of the supplied tasks.

    task taskY {
        mustRunAfter "taskX"
    }

For each supplied task, this action adds a task 'ordering', and does not specify a 'dependency' between the tasks. As such, it is still possible to execute 'taskY' without first executing the 'taskX' in the example.

See here for a description of the types of objects which can be used to specify an ordering relationship.

#### `void` `onlyIf`(`Closure` onlyIfClosure)

Execute the task only if the given closure returns true. The closure will be evaluated at task execution time, not during configuration. The closure will be passed a single parameter, this task. If the closure returns false, the task will be skipped.

You may add multiple such predicates. The task is skipped if any of the predicates return false.

Typical usage:`myTask.onlyIf{ dependsOnTaskDidWork() }`

#### `void` `onlyIf`(``Spec`<? super `Task`>` onlyIfSpec)

Execute the task only if the given spec is satisfied. The spec will be evaluated at task execution time, not during configuration. If the Spec is not satisfied, the task will be skipped.

You may add multiple such predicates. The task is skipped if any of the predicates return false.

Typical usage (from Java):

    myTask.onlyIf(new Spec<Task>() {
       boolean isSatisfiedBy(Task task) {
          return task.dependsOnTaskDidWork();
       }
    });

#### `Object` `property`(`String` propertyName)

Returns the value of the given property of this task. This method locates a property as follows:

1. If this task object has a property with the given name, return the value of the property.
2. If this task has an extension with the given name, return the extension.
3. If this task's convention object has a property with the given name, return the value of the property.
4. If this task has an extra property with the given name, return the value of the property.
5. If not found, throw `MissingPropertyException`

#### `void` `setProperty`(`String` name, `Object` value)

Sets a property of this task. This method searches for a property with the given name in the following locations, and sets the property on the first location where it finds the property.

1. The task object itself. For example, the `enabled` project property.
2. The task's convention object.
3. The task's extra properties.

If the property is not found, a `MissingPropertyException` is thrown.