Hello Group,
I have googled for this error and as far as I can see, the Appengine
Datastore does not support more than 5 Groups in a transaction (at least in
a XG Transaction).
OK ... but how do I get the the following issue done:
*1. I am using OpenSeccionInView Pattern. See my code below:*
@Override
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
//1. Create new EntityManager for this call
EntityManager em = factory.createEntityManager();
ThreadLocalEntityManager.set(em); //==(1) Create EM
em.getTransaction().begin(); //==(2) Begin Transaction
try {
chain.doFilter(request, response);
em.getTransaction().commit(); //==(3) Commit Transaction
} catch (ConstraintViolationException cve) {
//This exception is thrown on Constraint Violation JSR303
if(em.getTransaction().isActive()) {
//This is usually never called
em.getTransaction().rollback();
}
} catch (Exception e) {
if(em.getTransaction().isActive()) {
em.getTransaction().rollback();
}
e.printStackTrace();
} finally {
if(em.isOpen()) {
em.close(); //==(4) Close EM
}
}
}
*2. I have Entities called JobCategory that stays in OneToMany relation
with itself and OneToMany Relation with Job Entity
(JPA is used with DataNucleus)
*@Entity
public class JobCategory {
....
@OneToMany(mappedBy = "mainCategory", cascade = CascadeType.ALL)
@OrderBy("i18nKey ASC")
private List<JobCategory> subCategories = new ArrayList<JobCategory>();
@ManyToOne
private JobCategory mainCategory;
@OneToMany(mappedBy = "jobCategory")
@OrderBy("creationDate DESC")
private List<Job> jobs = new ArrayList<Job>();
...
/**
* Method will return All JobCategories that are available in the
database
*/
public static List<JobCategory> findAllJobCategories() {
EntityManager em = ThreadLocalEntityManager.get();
Query query = em.createQuery("SELECT e FROM " +
JobCategory.class.getSimpleName() + " e ORDER BY e.i18nKey");
return (List<JobCategory>) query.getResultList();
}
...
}
*My Question:*
I woudl like to load all JobCategories (there are more than 10 main
JobCategories with 5-6 Subcategories each), but as mentioned the DB does
not support more than 5 Groups per transaction.
The OSIV-Pattern, as shown in my code above and explained here:
https://community.jboss.org/wiki/OpenSessionInView?_sscc=t ... opens one
transaction for every DB-call which lets me get max 5 Grouped-Entities!?
How do I get *all JobCategories* loaded properly!?
I assume that there is something wrong with my OSIV-Pattern since it allows
only one transaction per call. But this is exactly what the JBOSS example
did!?
Thank you in advance for your help!!
Nermin
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