Instead of using the shell to create and launch tasks, you can use the Java-based DSL provided by the
The Java DSL for
TaskSchedule provides convenient wrappers around the
DataFlowTemplate class that enables creating, launching, and scheduling tasks programmatically.
To get started, you need to add the following dependency to your project:
<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-dataflow-rest-client</artifactId> <version>2.9.2</version> </dependency>
The classes at the heart of the Java DSL are
The task DSL also uses a few DataFlowTemplate classes, such as
The entry point is the
builder method on
TaskSchedule that takes an instance of a
The DSL for both the
Task and the
TaskSchedule requires a valid
Spring Cloud Data Flow offers the
DataFlowTemplate as an implementation of the
To create an instance of a
DataFlowTemplate, you need to provide a
URI location of the Data Flow Server.
Spring Boot auto-configuration for
DataFlowTemplate is also available.
You can use the properties in
DataFlowClientProperties to configure the connection to the Data Flow server.
Generally, you should start with the
URI dataFlowUri = URI.create("http://localhost:9393"); DataFlowOperations dataFlowOperations = new DataFlowTemplate(dataFlowUri);
You can create new
Task instances with the help of the
TaskBuilder class, which is returned from the
Consider the following example, which creates a new composed task:
dataFlowOperations.appRegistryOperations().importFromResource( "https://dataflow.spring.io/task-maven-latest", true); Task task = Task.builder(dataflowOperations) .name("myComposedTask") .definition("a: timestamp && b:timestamp") .description("My Composed Task") .build();
build method returns an instance of a
Task definition that represents a composed task that has been created but not launched.
timestamp used in the task definition refers to the task app name, as registered in DataFlow.
To create and launch your tasks, you need to make sure that the corresponding apps have been registered in the Data Flow server first, as shown Batch Developer Guide.
Attempting to launch a task that contains an unknown application throws an exception.
You can register your application by using the
DataFlowOperations, as follows:
dataFlowOperations.appRegistryOperations().importFromResource( "https://dataflow.spring.io/task-maven-latest", true);
Instead of creating a new Task, you can use the
TaskBuilder to retrieve an existing Task instance by name:
Optional<Task> task = Task.builder(dataflowOperations).findByName("myTask");
You can also list all existing tasks:
List<Task> tasks = Task.builder(dataflowOperations).allTasks();
Task instance, you have methods available to
destroy the task.
The following example launches the task:
long executionId = task.launch();
executionId is a unique Task execution identifier for the launched task.
launch method is overloaded to take a
java.util.Map<String, String> of launch properties and
java.util.List<String> of command line arguments.
The tasks are asynchronously run. If your use case requires you to wait on task completion or another task state, you can use the Java concurrency utilities or the
Awaitility library, as follows:
org.awaitility.Awaitility.await().until( () -> task.executionStatus(executionId) == TaskExecutionStatus.COMPLETE);
Task instance provides
stop methods to control and query the task.
Collection<TaskExecutionResource> executions() method lists all
TaskExecutionResource instances launched by the task. You can use the
executionId to retrieve the
TaskExecutionResource for a specific execution (
Optional<TaskExecutionResource> execution(long executionId)).
Collection<JobExecutionResource> jobExecutionResources() and
Collection<JobInstanceResource> jobInstanceResources() would let you introspect any Spring Batch Jobs when the task uses them.
Consider the following example, which creates a new task and schedules it:
Task task = Task.builder(dataflowOperations) .name("myTask") .definition("timestamp") .description("simple task") .build(); TaskSchedule schedule = TaskSchedule.builder(dataFlowOperations) .schedueName("mySchedule") .task(task) .build();
TaskSchedule.builder(dataFlowOperations) method returns the
build method returns an instance of a
TaskSchedule instance called
mySchedule, which is configured with a schedule instance.
At this point, the schedule has not been created.
You can use the
schedule() method to create the schedule:
schedule.schedule("56 20 ? * *", Collections.emptyMap());
You can also use the
unschedule() method to delete it:
You can use the
TaskScheduleBuilder to retrieve one or all of the existing schedulers:
Optional<TaskSchedule> retrievedSchedule = taskScheduleBuilder.findByScheduleName(schedule.getScheduleName()); List<TaskSchedule> allSchedulesPerTask = taskScheduleBuilder.list(task);
This section covers how to set deployment properties for
launch(Map<String, String> properties, List<String> arguments) method lets you customize how your tasks are launched.
We made it easier to create a map with properties by using a builder style and creating static methods for some properties so that you need not remember the names of the properties:
Map<String, String> taskLaunchProperties = new DeploymentPropertiesBuilder() .memory("myTask", 512) .put("app.timestamp.timestamp.format", "YYYY") .build(); long executionId = task.launch(taskLaunchProperties, Collections.EMPTY_LIST);
Similarly, you can set deployment properties for a
Map<String,String> props = new HashMap<>(); props.put("app.timestamp.timestamp.format", "YYYY"); taskSchedule.schedule("*/1 * * * *", props);