ejb3.0 deleting objects

[mravikrish]

Hello,

I am Ravi, I am having problem with deleting objects which are in relationships(one-many,many-many). ex : if i delete project object. all its associated objects should be deleted . my project object is associated to 3 objects(projectstatus,bid...).


any help appreciated.

Thank u
Ravi

[wolfgangknauf]

Hi Ravi,

the easiest way is to define a "Cascade" attribute on your relationship annotation:

@OneToMany(mappedBy="...", cascade=CascadeType.ALL, fetch=...)

It gets more complicated if you cannot simply cascade the deletes (would be no good idea on many-to-many relationships ;-) ). In this case, you have to cleanup both sides of the relation before deleting child or parent. So, if you have an entity "Parent" and an Entity "Child" with a bidirectional "ManyToMany" relationship, and you want to remove one child from the relationship (without deleting it), you would have to do this (snippet for a SessionBean which contains a reference to the entity manager):

Child child = this.entityManager.getReference(Child.class, childId );

Collection<Parent> listParents = child.getParents();
Iterator<Parent> iteratorParents = listParents.iterator();
while (iteratorParents.hasNext() == true)
{
 Parent parentForChild = iteratorParents.next();
 parentForChild.getChilds().remove(child);
}

this.entityManager.remove(child);

Hope this helps

As this question comes up quite often, it is maybe a good time to create a Wiki article about relationships ;-).

Wolfgang

[mravikrish]

thank you Wolfgang Knauf