Re: [eclipselink-users] Question on Eclipselink Internals

[Thilo Tanner <thilo.tanner@xxxxxxxxx>]

Hi Iaroslav,

thank you for your feedback. These are the transactions:

EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
A a = new A();
em.persists(a);

B b = new B();
b.setA(a);
em.persists(b);
em.getTransaction().commit();
em.close();

=== different thread ===

EntityManager em = emf.createEntityManager();
em.getTransaction().begin();
A a = em.find(A.class, 1);
a.getBs(); // list is empty


Best,
Thilo


2014-03-05 17:17 GMT+01:00 Iaroslav Savytskyi <iaroslav.savytskyi@xxxxxxxxxx>:
> Hi, Thilo
>
> What about transactions? Are you managing them manually? I mean is the transaction with a and b updates already committed when you are trying to access data from another session?
>
> Thanks.
> --
> Best regards.
> Iaroslav
>
>
> On 5 Mar 2014, at 12:34, Thilo Tanner <thilo.tanner@xxxxxxxxx> wrote:
>
>> Hi all,
>>
>> I mainly used Hibernate and Ebean in the last years. For a new project
>> I switched to Eclipselink and so far I'm very happy with the results.
>> The framework is much easier to use, especially if you want to map an
>> existing DB. Great job!
>>
>> One thing puzzles me concerning 1:N relationships. I have two very
>> simple classes:
>>
>> class A {
>>  @OneToMany(mappedBy = "a")
>>  private List<B> bs;
>>  ...
>> }
>>
>> class B {
>>  @ManyToOne
>>  private A a;
>>  ...
>> }
>>
>> It seems, that Eclipselink is caching the original object persisted
>> during runtime. So if I create objects
>>
>> A a = new A();
>> em.persists(a);
>>
>> B b = new B();
>> b.setA(a);
>> em.persists(b);
>>
>> When I access a from another session, I expected that a.getBs() is
>> filled with the b object created above, which isn't the case.
>> a.getBs() is empty, unless I create the back-link by hand during
>> creation:
>>
>> a.getBs().add(b)
>>
>> This is the correct and intended behavior for objects created during
>> runtime, correct? As long as the object isn't updated, I always get
>> the original object, I once created, from the session, right? Not that
>> this is an issue, it is just something worth to know when working with
>> the framework.
>>
>> Thanks for all your inputs!
>>
>> Best,
>> Thilo
>> _______________________________________________
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>
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