Removing entities in OneToMany with RequestFactory & JPA

[Roalt]

I would like to know what's the right way to remove a child from a one-to-many relation within GWT using the RequestFactory.

My GWT application with an Entity called Product and that product has a one-to-many relation to an Expert:

@Entity
public class Product {
    ... 
    OneToMany(mappedBy="product", orphanRemoval=true,
              cascade={CascadeType.DETACH,CascadeType.MERGE,CascadeType.PERSIST,CascadeType.REFRESH},fetch=FetchType.EAGER)
    Set<Expert> experts = new HashSet<Expert>();
    ...
}

@Entity(name = "EXPERT")
public class Expert {
    ...
    @ManyToOne(optional=false)
    Product product;
    ...
}

I have a user-interface where you can change some values of Product, but also a window where experts can be added or removed. Adding a Expert goes well, but how do I remove an expert? And what administration must I do on the client and server side?

I have already an opened productRequest going on.

I would appreciate all the help!

[Patrick Julien]

add CascadeType.Delete or use ALL, then removing the object from the collection will be sufficient to remove it from the underlying storage

product.getExperts().remove(expert);

[Roalt]

When I add the Cascade.REMOVE, I get the following error:

Caused by: javax.persistence.EntityNotFoundException: deleted entity
passed to persist: [myapplication.server.domain.Expert#<null>]

this happens after I called my save() function in
server.domain.Product.java:

em.getTransaction().begin();
em.merge(this);
em.getTransaction().commit();

...so that was the reason for me to remove the Cascade.REMOVE.

[Patrick Julien]

do you have nulls in your expert collection in your product object?

If you have detach in your CascadeType, it works anyway if you do this

product.getExperts().remove(expert);

em.merge(product);

em.remove(expert);

The remove cascade type removes the need for a distinct remove call.

[Patrick Julien]

In fact, you don't even need to call merge either since you're inside a transaction