JPA merge isn't working as expected - merge of object ignoring filled values from object

[Sean Van Buggenum]

hi all, 

I'm having trouble with the JPA EntityManager merge method. 

So far as I read, i.e., from sources such as stackoverflow

http://stackoverflow.com/questions/1069992/jpa-entitymanager-why-use-persist-over-merge

the merge method should be more helpful than it is appearing to me at the moment. 

I am attempting to write a new record to the database based on an object that I have no way of knowing is already persisted or not. 

The class is this:

@Entity
public class IdType implements Persistable
{
 /**
 * User specified Unique identifier.
 * Both idTypeCode and idCategory are together
 * a compound key, so as to ensure that the
 * combination of the both can not occur more
 * than once in the table.
 */
 @Id
 public String idTypeCode;
 @Id
 public IdCategory idCategory;
 
 public String idTypeName;
}

And when I call 'merge' on it, I get a big nasty stack trace about one of the id fields (from the composite idTypeCode and idCategory)   idtypeCode being null (which is not allowed, obviously). 

Yet I know the instance of this class DOES have a value for idTypeCode, as in my controller, I am binding the form and then for debugging purposes i'm sys-outing the values. 

The code:

 @Transactional
 public Result updateIds()
 {
 IdType idType = Form.form(IdType.class).bindFromRequest().get();


 System.out.println("idTypeCode is:  "+idType.idTypeCode);
 
 EntityManager em = entityManager();
 em.merge(idType);



 return redirect(routes.Application.index());
 }

The console:

idTypeCode is:  a-value-from-my-form
[error] - org.hibernate.engine.jdbc.spi.SqlExceptionHelper - NULL not allowed for column "ID_TYPE_CODE"; SQL statement:
insert into id_type (id_type_name, id_type_code, id_category) values (?, ?, ?) [23502-187]
[error] - play.core.server.netty.PlayDefaultUpstreamHandler - Cannot invoke the action
javax.persistence.RollbackException: Error while committing the transaction
 at org.hibernate.jpa.internal.TransactionImpl.commit(TransactionImpl.java:86) ~[hibernate-entitymanager-5.0.5.Final.jar:5.0.5.Final]
 at play.db.jpa.DefaultJPAApi.withTransaction(DefaultJPAApi.java:142) ~[play-java-jpa_2.11-2.4.4.jar:2.4.4]
 at play.db.jpa.JPA.withTransaction(JPA.java:159) ~[play-java-jpa_2.11-2.4.4.jar:2.4.4]
 at play.db.jpa.TransactionalAction.call(TransactionalAction.java:16) ~[play-java-jpa_2.11-2.4.4.jar:2.4.4]

Does anyone know the cause of this problem ? 

I hope I am not forced to call 'persist' instead, as I have no way of knowing if the entity exists already in the database. 

thanks for your help!

sean

[Sean Van Buggenum]

Not so easy a question eh?

I'm sorry if I phrased it incorrectly, or didn't get to the point as good as I should have. 

But I would like to hear anyway of success stories from people using pure JPA with Play, 

and how they got around the problem of a lack of a hibernate equivalent 'saveOrUpdate' method.

That was my hopes with the 'merge' method. However, honestly, I have not tested this (pure JPA using Hibernate) with a non-play project as yet to see how it behaves out of the 'play eco-system'. 

That will be my next step. And as soon as my boss allows me to dedicate more time (in about a week) I will be back at it. 

Until then, I'd love to hear of peoples success or lackthereof. 

Regards,

Sean

[Sean Van Buggenum]

UPDATE!!!!!

OK, finally got the time to look further into this myself. It seems this has nothing to do with play. I tested just now the same scenario with a straight JPA/Hibernate console app. I get the same problem. The problem occurs as soon as I have a composite key (as I do in the given example). As soon as I remove one of the columns as key, the merge will work. Now I am investigating why that is, and how to avoid the issue (while still having the model I need). I will update this issue as soon as I have more information.

On Thursday, 14 January 2016 18:10:31 UTC+1, Sean Van Buggenum wrote:

[Sean Van Buggenum]

OK. So I worked it out finally.

It seems like I was constructing my JPA compound primary key incorrectly. 

I thought I could simply specify my compound key with the Id annotation alone. Like so:

@Entity

public class IdType implements Serializable

{

/**

* User specified Unique identifier.

* Both idTypeCode and idCategory are together

* a compound key, so as to ensure that the 

* combination of the both can not occur more

* than once in the table.

*/

@Id

public String idTypeCode;

@Id

public IdCategory idCategory;

public String idTypeName;

}

But I was wrong. 

I need to use a separate IdClass. Otherwise, I get cryptic error messages as described earlier. 

Now my class(es) look like this:

@Entity @IdClass(IdTypeCompoundId.class)

public class IdType implements Serializable

{

/**

* User specified Unique identifier.

* Both idTypeCode and idCategory are together

* a compound key, so as to ensure that the 

* combination of the both can not occur more

* than once in the table.

*/

@Id

public String idTypeCode;

@Id

public IdCategory idCategory;

public String idTypeName;

}

public class IdTypeCompoundId implements Serializable

{

public String idTypeCode;

public IdCategory idCategory;

}

and it is all happy.  Merge goes through without problems. 

pwew!

On Thursday, 14 January 2016 18:10:31 UTC+1, Sean Van Buggenum wrote: