Question

I have a business object that exposes a list of elements for which want to have control on.

For that, I have created a custom List implementation (CustomList) with a listener to be notified whenever an an element added / removed.

public class MyClass {
    private List<ItemClass> list;

    public MyClass() {
        this.list = new CustomList<ItemClass>();
    }

    public List<ItemClass> getList() {...}
    public setList(List<ItemClass>) {...}
}

The problem is that, if I want to persist this object, Hibernate uses the setter to set the list with its own List implementation, thus short-circuiting my nice CostumList bahavior.

I have tried to cheat with the setter, this way :

public setList(List<ItemClass> newList) {
    this.list.clean():
    this.list.addAll(newList);
}

But this does not work either :
Hibernate calls the setter first, and then add some elements to its own list. Therefore, I end up with an empty list on my side.

Is there a way I can ask hibernate to use my custom list implementation ? Or to fill it after has loaded the contents ?

Thanks in advance for your help.

Answer 1

My first thought was to do something like this:

You could always use the setter to change the list implementation
(similar to what you have done). For instance:

public setList(List<ItemClass> newList) {
    // Sets the list as a custom list.
    list = new CustomList<>(newList);
}

Yet, for that to work, you need to change the implementation of your
CustomList to work as a decorator, so it will work independently of the wrapped list type.

As @millimoose has noticed, it still does not solve your problem.

A working solution could be found by using the Hibernate (or JPA) lifecycle annotations (such as @PostPersist, @PostUpdate or @PostLoad…). So, you could use that customList.addAll() solution (after the entity has been updated, persisted or loaded).