Update exiting BLOB does not work

[carstenrudat]

Hi all,

I have a problem updating a existing or null BLOB. I run jboss-4.2.1.GA (all-config) with its EJB3 implementation and MySQL 5.x with mysql-connector-java-5.0.7-bin.jar-driver.

I have an entity Signature with a unidirectional relationship to Image (which holds the BLOB):

public class Signature ...

 @OneToOne(cascade = {CascadeType.PERSIST, CascadeType.MERGE}, fetch = FetchType.EAGER)
 @JoinColumns({
 @JoinColumn(name="image_id_fk", referencedColumnName="id")
 })
 public com.genloop.base.ImageImpl getImage() {
 return this.image;
 }


public class Image ...

 @Lob
 @Column(name = "image", columnDefinition="MEDIUMBLOB")
 //@org.hibernate.annotations.Cache(usage = org.hibernate.annotations.CacheConcurrencyStrategy.NONE) -> I tried this
 public java.sql.Blob getImage() {
 return this.image;
 }

In a SLSB, I try a entityManager.merge(aSignagure) and all changes of Signature and Image (e.g. a field "fileName") will update to the DB, except. The BLOB.

I have done a little debugging and I saw, that the getImage() was not called after entityManager.merge(). Then I can see something about XYZLoader that (I think so...) fills the entity-bean with the data of the database. This trace calls setImage(Blob) with the old BLOB or (if it was null) with null.

What could I do?

Thanks,
Carsten

[carstenrudat]

Hi,

I tried this with Oracle Express (latest version/very new oracle-driver).

It doesn't work with Oracle, too, so I think it is

a) a failure of my code/understanding of merge and cascade
b) a bug in Hibernate?

Any ideas - please ;-)

Carsten

[carstenrudat]

Hi all,

I have tested this with Hibernate directly.

a) If I set the blob while my entity (Signature) is attached to a EntityManager-Session, my new blob will be updated to the database

b) If I set the blob while it is not attached, then reattache to a new session and calling a EntityManager.merge(signature) the blob will not be updatet to the database.

Is a) the only way to update a blob? If I create a new Signature with a Blob (not attached) and call EntityManager.perist(signature), my blob will also be inserted. So, why does update causes these problems?

Thanks,
Carsten

[carstenrudat]

...debugging Hibernate - BlobType.replace says:

public Object replace(Object original, Object target, SessionImplementor session, Object owner, Map copyCache) throws HibernateException {
 //Blobs are ignored by merge()
 return target;
}

"It's not a bug - it's feature"?!