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From "Howard W. Smith, Jr." <smithh032...@gmail.com>
Subject Re: question around entityManager.flush
Date Wed, 21 May 2014 19:40:54 GMT
hmmm, create -> edit is useless?

I guess you are saying that after i 'create', even though I am adding a
related entity (e.g. tree 'has' branch).

create(tree)

Branch branch = new Branch(1)
tree.addBranch(branch)

so, you are saying that the edit(tree) is not necessary? is that the cause
of the issue that i experience when I remove entityManager.flush() ?




On Wed, May 21, 2014 at 3:31 PM, Romain Manni-Bucau
<rmannibucau@gmail.com>wrote:

> then the issue is the code you do needs atomicity for each JPA operation
> (why you use flush). but this shouldn't be needed. Typically: create ->
> edit is useless. Just create it once ;)
>
>
>
> Romain Manni-Bucau
> Twitter: @rmannibucau
> Blog: http://rmannibucau.wordpress.com/
> LinkedIn: http://fr.linkedin.com/in/rmannibucau
> Github: https://github.com/rmannibucau
>
>
> 2014-05-21 21:29 GMT+02:00 Howard W. Smith, Jr. <smithh032772@gmail.com>:
>
> > okay, based on what you said below,
> >
> > On Wed, May 21, 2014 at 2:42 PM, Romain Manni-Bucau
> > <rmannibucau@gmail.com>wrote:
> >
> > > @Stateless // or singletong
> > > public class TxBean {
> > >    @PersistenceContext EntityManager em;
> > >
> > >     public void doSomeStuffAndCommit() {
> > >         // em usage
> > >     }
> > > }
> > >
> > >
> > > when exiting the method commit will trigger flush
> > >
> >
> > my @Stateless EJB has doSomeStuffAndCommit(), but doSomeStuffAndCommit()
> is
> > 'usually' SQL SELECTs, and in my Abstract class for @Stateless @EJB, I
> have
> > the following:
> >
> >     protected abstract EntityManager getEntityManager();
> >
> >     public void create(T entity) {
> >         // 2011-09-17 flush immediately after persist/create
> >         getEntityManager().persist(entity);
> >         getEntityManager().flush();
> >     }
> >
> >     public void create(T entity, Boolean flush) {
> >         getEntityManager().persist(entity);
> >         if (flush) getEntityManager().flush();
> >     }
> >
> >     public void edit(T entity) {
> >         // 2011-09-17 flush immediately after merge
> >         getEntityManager().merge(entity);
> >         getEntityManager().flush();
> >     }
> >
> >     public void edit(T entity, Boolean flush) {
> >         getEntityManager().merge(entity);
> >         if (flush) getEntityManager().flush();
> >     }
> >
> >     public void flush() {
> >         getEntityManager().flush();
> >     }
> >
> >     public void remove(T entity) {
> >         // 2011-09-17 flush immediately after remove/merge the
> > managed/detached entity
> >         getEntityManager().remove(getEntityManager().merge(entity));
> >         getEntityManager().flush();
> >     }
> >
> >     public void remove(T entity, Boolean flush) {
> >         getEntityManager().remove(getEntityManager().merge(entity));
> >         if (flush) getEntityManager().flush();
> >     }
> >
> >
> > majority of my app, calls the create(T entity), edit(T entity), and
> > remove(T entity) methods above where flush() is called after the
> > entityManager operation.
> >
> > below, is a method I have in a @Singleton bean that is called via
> @Schedule
> > to get some data from email account and write data to database.
> >
> > again, the method below is only one of the methods that is in the
> > @Singleton bean.
> >
> >     private void createAuditTrail(String relatedEntityName,
> >                                  Object relatedEntityObj,
> >                                  String description) {
> >
> >         AuditTrail current = new AuditTrail();
> >         current.setDescriptionTx(description);
> >         try {
> >             Users user = getUser("system");
> >             if (user == null) {
> >                 logger.info("Error adding AUDIT TRAIL; 'system' user
> does
> > not exist");
> >                 return;
> >             }
> >             current.setUserName(user);
> >             current.setAuditTrailId(1);
> >             current.setAuditTrailDt(new Date());
> >             ejbFacadeAuditTrail.create(current);
> >             // add auditTrail to order
> >             if (relatedEntityName.equals("orders")) {
> >                 Orders order = (Orders) relatedEntityObj;
> >                 current.addOrder(order);
> >                 ejbFacadeAuditTrail.edit(current);
> >             }
> >         } catch (Exception e) {
> >             logger.info("Error adding AUDIT TRAIL" +
> >                         (e.getMessage() != null ? "; " + e.getMessage() :
> > ""));
> >         }
> >     }
> >
> >
> > Majority of my app is CDI @SessionScoped or @ViewScoped beans that call
> > @Stateless @EJB to select/create/update/delete data in database.
> >
> > CDI @SessionScoped and @ViewScoped beans will get data via @Stateless
> @EJB,
> > and CDI @SessionScoped and @ViewScoped beans may do some data
> manipulation,
> > and then @Stateless @EJB is called to do the entityManager create(),
> > edit(), remove() to update database, accordingly.
> >
> > The only time I write a lot of logic in @EJBs is when I am preparing for
> > SQL SELECT.
> >
> > The @Singleton bean example code that I provided above is one of only
> > (@Singleton) @EJBs that have a lot of code that does a specific job.
> >
> > So, when I removed entityManager.flush() from my Abstract class, earlier,
> > per Jean-Louis's recommendation, some data was saved to database by
> > @Singleton and most of the data was 'not' saved to database.
> >
> > Definition of @Singleton is below:
> >
> > @Singleton
> > @Lock(LockType.WRITE)
> > @AccessTimeout(value = 2, unit = TimeUnit.MINUTES)
> > public class AddEmailRequest {
> >
>

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