Spring JPA - deleting child element doesn't reflect in database table

Question

I'm having problems deleting the child element of a one-to-many relationship entity. Here's a code snippet:

@Override
@Transactional
public void deleteTask(UUID listId, UUID taskId) {
    TaskList list = repo.findOne(listId);

    System.out.println("Old List: " + list);

    for(Task t : list.getTasks()) {
        if(t.getId().toString().equals(taskId.toString())) {
            System.out.println(list.getTasks().remove(t));
            System.out.println("Task with id " + taskId + " deleted.");
        }
    }
    System.out.println("New List: " + repo.save(list));
}

The Task class is this:

@Entity(name = "task")
public class Task implements Serializable {    

    // Id and 3 fields

    @ManyToOne
    @JoinColumn(name="tasklist_id")
    private TaskList parentList;

    // 3 more fields

    // Constructor
    public Task() {}

    //Getters and Setters
}

and the TaskList class is this:

@Entity(name = "task_list")
public class TaskList implements Serializable {

    // Id and two fields

    @OneToMany(mappedBy="parentList", cascade={CascadeType.ALL})
    private List<Task> tasks;

    // Constructor
    public TaskList() {}
}

The Task entity is the child, and even though the save() function returns the truncated TaskList, I can't get the changes to show in a separate query to the database. The number of tasks remains the same. However, deleting a list through repo.delete(listId) works fine with both the list and its tasks gone.

Here, repo is a repository corresponding to the parent TaskList class. All operations to the child Task class happen through a @OneToMany({cascade=CascadeType.ALL}) relation.

For some reason, searching for all TaskLists using repo.findAll() also returns faulty results.

I'm obviously doing something fundamentally wrong. Please tell me what to do.

Answer 1

You need to add orphanRemoval = true to your mapping:

@OneToMany(mappedBy="parentList", cascade={CascadeType.ALL}, orphanRemoval=true)

list.getTasks().remove(t) just removes entity from the collection, so you need to tell JPA to remove it also from DB. This is done by the orphanRemoval attribute.