Spring Cloud Task uses a datasource for storing the results of task executions. By default, we provide an in-memory instance of H2 to provide a simple method of bootstrapping development. However, in a production environment, you probably want to configure your own DataSource.

If your application uses only a single DataSource and that serves as both your business schema and the task repository, all you need to do is provide any DataSource (the easiest way to do so is through Spring Boot’s configuration conventions). This DataSource is automatically used by Spring Cloud Task for the repository.

If your application uses more than one DataSource, you need to configure the task repository with the appropriate DataSource. This customization can be done through an implementation of TaskConfigurer.

One modifiable property of TaskRepository is the table prefix for the task tables. By default, they are all prefaced with TASK_. TASK_EXECUTION and TASK_EXECUTION_PARAMS are two examples. However, there are potential reasons to modify this prefix. If the schema name needs to be prepended to the table names or if more than one set of task tables is needed within the same schema, you must change the table prefix. You can do so by setting the spring.cloud.task.tablePrefix to the prefix you need, as follows:

spring.cloud.task.tablePrefix=yourPrefix

In cases where you are creating the task tables and do not wish for Spring Cloud Task to create them at task startup, set the spring.cloud.task.initialize.enable property to false, as follows:

spring.cloud.task.initialize.enable=false

It defaults to true.

In some cases, you may want to allow for the time difference between when a task is requested and when the infrastructure actually launches it. Spring Cloud Task lets you create a TaskExecution when the task is requested. Then pass the execution ID of the generated TaskExecution to the task so that it can update the TaskExecution through the task’s lifecycle.

A TaskExecution can be created by calling the createTaskExecution method on an implementation of the TaskRepository that references the datastore that holds the TaskExecution objects.

In order to configure your Task to use a generated TaskExecutionId, add the following property:

spring.cloud.task.executionid=yourtaskId

Spring Cloud Task lets you store an external task ID for each TaskExecution. An example of this would be a task ID provided by Cloud Foundry when a task is launched on the platform. In order to configure your Task to use a generated TaskExecutionId, add the following property:

spring.cloud.task.external-execution-id=<externalTaskId>

Spring Cloud Task lets you store a parent task ID for each TaskExecution. An example of this would be a task that executes another task or tasks and you want to record which task launched each of the child tasks. In order to configure your Task to set a parent TaskExecutionId add the following property on the child task:

spring.cloud.task.parent-execution-id=<parentExecutionTaskId>

The TaskConfigurer is a strategy interface that lets you customize the way components of Spring Cloud Task are configured. By default, we provide the DefaultTaskConfigurer that provides logical defaults: Map-based in-memory components (useful for development if no DataSource is provided) and JDBC based components (useful if there is a DataSource available).

The TaskConfigurer lets you configure three main components:

You can customize any of the components described in the preceding table by creating a custom implementation of the TaskConfigurer interface. Typically, extending the DefaultTaskConfigurer (which is provided if a TaskConfigurer is not found) and overriding the required getter is sufficient. However, implementing your own from scratch may be required.

	Note
	Users should not directly use getter methods from a TaskConfigurer directly unless they are using it to supply implementations to be exposed as Spring Beans.

In most cases, the name of the task is the application name as configured in Spring Boot. However, there are some cases where you may want to map the run of a task to a different name. Spring Cloud Data Flow is an example of this (because you probably want the task to be run with the name of the task definition). Because of this, we offer the ability to customize how the task is named, through the TaskNameResolver interface.

By default, Spring Cloud Task provides the SimpleTaskNameResolver, which uses the following options (in order of precedence):

TaskExecutionListener lets you register listeners for specific events that occur during the task lifecycle. To do so, create a class that implements the TaskExecutionListener interface. The class that implements the TaskExecutionListener interface is notified of the following events:

Spring Cloud Task also lets you add TaskExecution Listeners to methods within a bean by using the following method annotations:

The following example shows the three annotations in use:

 public class MyBean {

	@BeforeTask
	public void methodA(TaskExecution taskExecution) {
	}

	@AfterTask
	public void methodB(TaskExecution taskExecution) {
	}

	@FailedTask
	public void methodC(TaskExecution taskExecution, Throwable throwable) {
	}
}

	Note
	Inserting an ApplicationListener earlier in the chain than TaskLifecycleListener exists may cause unexpected effects.

8.9.1 Exceptions Thrown by Task Execution Listener

If an exception is thrown by a TaskExecutionListener event handler, all listener processing for that event handler stops. For example, if three onTaskStartup listeners have started and the first onTaskStartup event handler throws an exception, the other two onTaskStartup methods are not called. However, the other event handlers (onTaskEnd and onTaskFailed) for the TaskExecutionListeners are called.

The exit code returned when a exception is thrown by a TaskExecutionListener event handler is the exit code that was reported by the ExitCodeEvent. If no ExitCodeEvent is emitted, the Exception thrown is evaluated to see if it is of type ExitCodeGenerator. If so, it returns the exit code from the ExitCodeGenerator. Otherwise, 1 is returned.

In the case that an exception is thrown in an onTaskStartup method, the exit code for the application will be 1. If an exception is thrown in either a onTaskEnd or onTaskFailed method, the exit code for the application will be the one established using the rules enumerated above.

	Note
	In the case of an exception being thrown in a onTaskStartup, onTaskEnd, or onTaskFailed you can not override the exit code for the application using ExitCodeExceptionMapper.

@AfterTask
public void afterMe(TaskExecution taskExecution) {
    taskExecution.setExitMessage("AFTER EXIT MESSAGE");
}

Spring Cloud Task lets you establish that only one task with a given task name can be run at a time. To do so, you need to establish the task name and set spring.cloud.task.single-instance-enabled=true for each task execution. While the first task execution is running, any other time you try to run a task with the same task name and`spring.cloud.task.single-instance-enabled=true`, the task fails with the following error message: Task with name "application" is already running. The default value for spring.cloud.task.single-instance-enabled is false. The following example shows how to set spring.cloud.task.single-instance-enabled to true:

spring.cloud.task.single-instance-enabled=true or false

To use this feature, you must add the following Spring Integration dependencies to your application:

<dependency>
    <groupId>org.springframework.integration</groupId>
    <artifactId>spring-integration-core</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.integration</groupId>
    <artifactId>spring-integration-jdbc</artifactId>
</dependency>

	Note
	The exit code for the application will be 1 if the task fails because this feature is enabled and another task is running with the same task name.

In cases where Spring Cloud Task should not be auto configured for an implementation, you can disable Task’s auto configuration. This can be done either by adding the following annotation to your Task application:

@EnableAutoConfiguration(exclude={SimpleTaskAutoConfiguration.class})

You may also disable Task auto configuration by setting the spring.cloud.task.autoconfiguration.enabled property to false.