Support multiple TaskDecorators in TaskExecutionAutoConfiguration

[ttddyy]

TaskExecutionAutoConfiguration currently only take single TaskDecorator bean.
This is because there is no implementation that represents multiple TaskDeorators. (e.g.: CompositeTaskDecorator).

I handle this by creating CompositeTaskDecorator:

public class CompositeTaskDecorator implements TaskDecorator {
    private List<TaskDecorator> taskDecorators = new ArrayList<>();

    public CompositeTaskDecorator(Collection<? extends TaskDecorator> taskDecorators) {
        this.taskDecorators.addAll(taskDecorators);
    }

    public CompositeTaskDecorator(TaskDecorator... taskDecorators) {
        this.taskDecorators.addAll(Arrays.asList(taskDecorators));
    }

    public boolean add(TaskDecorator taskDecorator) {
        return this.taskDecorators.add(taskDecorator);
    }

    @Override
    public Runnable decorate(Runnable runnable) {
        for (TaskDecorator taskDecorator : this.taskDecorators) {
            runnable = taskDecorator.decorate(runnable);
        }
        return runnable;
    }
}

I believe it is pretty common to have usecases to apply multiple TaskDecorators; so, it is nice if CompositeTaskDecorator is available in either spring or spring-boot.

Then, if such class is available, TaskExecutionAutoConfiguration(TaskExecutorBuilder) can detect multiple task decorators.

TaskDecorator taskDecorator(ObjectProvider<TaskDecorator> taskDeorators) {
  return new CompositeTaskDecorator(taskDeorators.orderedStream().collect(Collectors.toList()));
}

[snicoll]

I've moved that suggestion to Spring Framework. If it turns out this gets added in the core container, we can make the necessary changes in Spring Boot.

[cptully]

This is an old issue, any movement? I'm glad I googled, because I was about to run into the exact issue solved by this PR!

[sbrannen]

This is an old issue, any movement?

We'll discuss it within the team.

[cptully]

Great!

[snicoll]

Closing in favor of PR #23692