[News.eclipse.technology.eclipselink] JPA: merging + cascade

[Sebastian Fuchs <sf@xxxxxxxxxxxxxxxxxxx>]

Hello,

Just a JPA question about cascading merge.
Please imagine the following situation:


                        A
            -----------------------------
           /                              \
      1 ---                                ---->n
root                                                 child
      1---                                 ---->n
          \B                            C /
           ----->n   subgroup   1--------


I want to merge a detached graph to the persistence context.
There should be cascading that way, that em#merge() should only be 
called for the root element.

All child entities belong to the root object. Therefore collection A is 
annotated with
@OneToMany(cascade = CascadeType.ALL).

All subgroup entities belong to the root object. Therefore collection B 
is annotated with
@OneToMany(cascade = CascadeType.ALL) too.

Collection C contains some child entities from the root's collection.

How should I annotade C so, that when there is one NEW child entity 
referenced by A AND C there is exactly one new managed entity created ?

@OneToMany  works as well as
@OneToMany(cascade = CascadeType.MERGE)
but I am not sure what is correct.

The spec says nothing about that situation or I missed it.

From the specs:

For all entities Y referenced by relationships from X having the cascade 
element value
cascade=MERGE or cascade=ALL, Y is merged recursively as Y'. For all 
such Y referenced
by X, X' is set to reference Y'. (Note that if X is managed then X is 
the same object as
X'.)
-----> not sure wheter there are 2 entities created by accident when 
annotating with @OneToMany(cascade = CascadeType.MERGE)

If X is an entity merged to X', with a reference to another entity Y, 
where cascade=MERGE
or cascade=ALL is not specified, then navigation of the same association 
from X' yields a
reference to a managed object Y' with the same persistent identity as Y.
-----> not sure what persistent identity Y has when it is new
when using @OneToMany

I'm currently using TopLink Essentials.
Thank you,

Sebastian