Entity data reset when a lazy LOB is changed - eclipselink

Question

I'm working on a big project using Glassfish 4 (JavaEE7) and EclipseLink (JPA2.1).
When I modify the value of a LOB field, this resets all the previous value of then entity.
For instance, I have the following entity:
#Entity
#Table(name="person")
public class Person implements Serializable {
#Id
#Column(name = "ID")
private Integer id;
#Column(name = "LASTNAME")
private String lastname;
#Column(name = "FIRSTNAME")
private String firstname;
#Column(name = "VERSION")
private Integer version;
#Lob
#Basic(fetch = FetchType.LAZY)
#Column(name = "REMARKS")
private String remarks;
/* getter & setters */
}
I use the following code to update my entity:
#Singleton
#TransactionManagement(TransactionManagementType.BEAN)
#Startup
public class ModifierBean implements ModifierBeanLocal {
#Resource
private UserTransaction userTransaction;
#PersistenceContext
private EntityManager entityManager;
#Override
public String modify(Integer id, String lastname, String firstname, String remarks) {
try {
StringBuilder result = new StringBuilder(256);
userTransaction.begin();
Query query = entityManager.createQuery("SELECT p FROM Person p WHERE p.id = ?1");
query.setParameter(1, id);
Person p = (Person)query.getSingleResult();
result.append("State 0: lastname=").append(p.getLastname()).append(", firstname=").append(p.getFirstname()).append(", version=").append(p.getVersion()).append("<br />");
p.setFirstname(firstname);
p.setLastname(lastname);
p.setVersion(p.getVersion()+1);
result.append("State 1: lastname=").append(p.getLastname()).append(", firstname=").append(p.getFirstname()).append(", version=").append(p.getVersion()).append("<br />");
p.setRemarks(remarks); // <= reset the other fields
result.append("State 2: lastname=").append(p.getLastname()).append(", firstname=").append(p.getFirstname()).append(", version=").append(p.getVersion()).append("<br />");
userTransaction.commit();
return result.toString();
} catch(Exception e) {
//...
}
}
}
When I'm running the following code, here is the output I get from the Bean:
State 0: lastname=Smith, firstname=John, version=0
State 1: lastname=John2, firstname=Smith2, version=1
State 2: lastname=Smith, firstname=John, version=0
As one can see, the values of then entity are reset when LOB is loaded, which is very annoying for my purpose.
There are some tricks to prevent that to happen, for instance I tested the following options:
call entityManager.flush() just before the modification of the LOB field
call p.getRemarks() juste before doing the first modifications
I also noticed that if the LOB field is not changed, then the values are correctly committed.
I know that a LAZY value is loaded on demand but I do not understand why it resets all the other values.
Is this a bug or a standard behaviour ? Is there any way to make it work as expected (no reset of value) ?

Answer 1

I just found out that this exact bug has been open in EclipseLink (already present since v2.1.3): https://bugs.eclipse.org/bugs/show_bug.cgi?id=371743

Answer 2

It would depend on your persistence unit properties and it's assocation to the transaction. I believe though, since you haven't explicietely joined the EntityManager to the transaction, the Em is behaving as if it is outside the transaction causing the following behavior to apply:
"Outside transaction entire object (fetch group members included) is refreshed in the shared cache."
http://wiki.eclipse.org/EclipseLink/Development/2.1/AdvancedJPA_Queries/FetchGroup
Try calling entityManager.joinTransaction(); after starting the transaction to see if this helps. EclipseLink