Run nested task in custom task

I have written my own ANT task to perform some function. However, I need this task to invoke a java task as a nest task. So I have the following code in my build file:

<mytask ... >
  <java ... />
</mytask>

I would like to run a piece of code after the java task finishes executing but before mytask completes, for the purpose of cleanup.

Is this a broken design, not recommended in build files? If not, which method should I over-ride in order to run the cleanup method?

Solution

Let your task implement the org.apache.tools.ant.TaskContainer interface, write your own addTask(Task task) method.

For example (it should only take a task named "java"):

private List<Task> _nestedTask = new ArrayList<>();

public void addTask(Task task) {
    if (task.getTaskName().equals("java")) {
        _nestedTasks.add(task);
    }
    else {
        throw new BuildException("Support only nested <java> task.");
    }
}

Please note that if you write multiple nested <java> tasks in your build file, you need to handle them by your self. To execute the nested <java> tasks, just iterate through the list and call execute() method for each task.

Update:

When a nested task is added, it doesn't run automatically. It won't even run if its execute() method is not called in your custom task.

So... A very basic and simple example:

// your custom task's execute...
public void execute() {
    //do something

    for (Task task : _nestedTask) {
        task.perform(); // here the nested task is executed.
    }

    //do something
}