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Hibernate throws error (Detached entity) while trying to retrieve data

While trying to update entity I'm first retrieving it from the database, then I'm mapping the TO from frontend on it using Orika Mapper.
Then I'm trying to retrieve some data not related to this entity using 'JpaRepository' and findAllByOrderByCode method. And while this operation I'm getting a strange error saying that: "An unexpected exception occurred: detached entity passed to persist:".
And this error refers not to the basic field from the entity but to the object from the collection from this entity.
Summarize:
I have entity A which have bidirectional mapping One to Many to the entity B:
class A {
List<B> b;
}
then I want to update whole A with an object from frontend which I mapped using Orika Mapper.
And while trying to get some data I have an error.
I found that Orika by default makes a deep copy for collections so entityA = customsClearanceOrderRepository.findById(requestTo.getId());
entityA which has List of entitiesB and which are tracked and included in persistence context is replaced with a deep copy of them so they have another address and it means their aren't any longer tracked by Hibernate.
So I tried to map those collections by myself, to just update the fields and not create a new object and then the problem has gone.
Everything would be fine but when I removed this line List<SthTo> all = someRefersToDb.findAllByOrderByCode(); // error appears here
then the problem also doesn't exist, even that I'm again using orika which makes this deep copy. And I understand that it works fine because of 'saveAndFlush' in fact while updating makes EntityManager.merge(entity) and the problem with another address for entities is not a problem for that (cause it copies not tracked object into persistence context).
entityA = entityARepository.findById(requestTo.getId());
entityAMapper.map(requestTo, entityA);
List<SthTo> all = someRefersToDb.findAllByOrderByCode(); // error appears here
EntityA entityASaved = entityARepository.saveAndFlush(entityA);
So I want to know what's going on here: someRefersToDb.findAllByOrderByCode();
Is there some kind of checking the state of the entityA?
Everything is by default, I mean there is no magical #Transactional(propagation = Propagation.REQUIRES_NEW) or sth like this.

I know why!
Hibernate while running someRefersToDb.findAllByOrderByCode();
in fact, call also session.flush() which is used to synchronize session data with the database. And since Orika changed the addresses of entities their aren't any longer a part of the persistence context and the synchronization fails.

How to disable auto update in hibernate/JPA

Is it possible to stop hibernate from auto updating a persistent object?
#Transactional
public ResultTO updateRecord(RequestTO requestTO) {
Entity entity = dao.getEntityById(requestTO.getId());
// now update the entity based on the data in the requestTO
ValidationResult validationResult = runValidation(entity);
if(validationResult.hasErrors()) {
// return ResultTO with validation errors
} else {
dao.persist(entity);
}
}
Here is what happens in the code, I retrieve the entity which would be considered by hibernate to be in persistent state, then I update some of the fields in the entity, then pass the entity to validation. if validation fails, then don't udpate, if validation succeeds then persist the entity.
Here is the main issue with this flow: because I updated the entity for it to be used in the validation, it does not matter whether I call persist() method (on the DAO) or not, the record will always be updated because hibernate detects that the entity has been changed and flags it for update.
Keep im mind I can change the way i do validation and work around the issue, so I'm not interested in workarounds. I'm interested in knowing how i would be able to disable the hibernate feature where it automatically updates persistent objects.
Please keep in mind I'm using hibernates' implementation of JPA. so Hibernate specific answers dealing with hibernate specific API will not work for me.
I tried to look for hibernate configuration and see if I can set any configuration to stop this behavior but no luck.
Thanks
--EDIT ---
I couldn't find a solution to this, so I opted to rolling back the transaction without throwing any RuntimeException even though I'm in a declarative transaction using:
TransactionInterceptor.currentTransactionStatus().setRollbackOnly();
which works like a charm.

Configure FlushMode for your session.
http://docs.jboss.org/hibernate/orm/3.5/api/org/hibernate/FlushMode.html

You can use EntityManager.clear() method after getting object from database.
http://docs.oracle.com/javaee/6/api/javax/persistence/EntityManager.html#clear()

You can call the following code:
TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();

Throw an exception if validation fails and have the caller handle that.

Reattach and lazy load exception

I am facing a lazy load exception which I cannot figure out.
First I fetch with a usual find method from the entity manager an entity. After that I run method which part of it is :
object = getUnproxiedValue(object);
if (object == null) {
... // this part is not run
return;
}
if (object instanceof Collection ) {
... // and I fall here with lazy load exception
return;
}
The getUnproxiedValue suppose to give object when the argument object is a proxy, the proxy is initialized (loaded) and the un-wrapped object is returned. Something goes wrong beacuse when there is a collection sometimes it dies with an lazy load exception, beacuse object is null so why the first condition did not work ?
For any clues and hints thank you in advance, and I really greatly appreciate any support in this.
Regards,
P.

LazyLoadingException identifes that you're trying to get data from db without a transaction. Try use #TransactionAttribute annotation to ensure you run your if (object instanceof Collection ) { block in transaction.

Are you using EJB Beans? Your entity Object is detached, when you leave the transaction. So you cannot load any dependent Entities (lazy Loading). You could use an extended persistence context entity manager together with a stateful session bean. Then you can use lazy loading outside a transaction. And your Entity is keep in sync with the database.

What is the proper way to re-attach detached objects in Hibernate?

I have a situation in which I need to re-attach detached objects to a hibernate session, although an object of the same identity MAY already exist in the session, which will cause errors.
Right now, I can do one of two things.
getHibernateTemplate().update( obj )
This works if and only if an object doesn't already exist in the hibernate session. Exceptions are thrown stating an object with the given identifier already exists in the session when I need it later.
getHibernateTemplate().merge( obj )
This works if and only if an object exists in the hibernate session. Exceptions are thrown when I need the object to be in a session later if I use this.
Given these two scenarios, how can I generically attach sessions to objects? I don't want to use exceptions to control the flow of this problem's solution, as there must be a more elegant solution...

So it seems that there is no way to reattach a stale detached entity in JPA.
merge() will push the stale state to the DB,
and overwrite any intervening updates.
refresh() cannot be called on a detached entity.
lock() cannot be called on a detached entity,
and even if it could, and it did reattach the entity,
calling 'lock' with argument 'LockMode.NONE'
implying that you are locking, but not locking,
is the most counterintuitive piece of API design I've ever seen.
So you are stuck.
There's an detach() method, but no attach() or reattach().
An obvious step in the object lifecycle is not available to you.
Judging by the number of similar questions about JPA,
it seems that even if JPA does claim to have a coherent model,
it most certainly does not match the mental model of most programmers,
who have been cursed to waste many hours trying understand
how to get JPA to do the simplest things, and end up with cache
management code all over their applications.
It seems the only way to do it is discard your stale detached entity
and do a find query with the same id, that will hit the L2 or the DB.
Mik

All of these answers miss an important distinction. update() is used to (re)attach your object graph to a Session. The objects you pass it are the ones that are made managed.
merge() is actually not a (re)attachment API. Notice merge() has a return value? That's because it returns you the managed graph, which may not be the graph you passed it. merge() is a JPA API and its behavior is governed by the JPA spec. If the object you pass in to merge() is already managed (already associated with the Session) then that's the graph Hibernate works with; the object passed in is the same object returned from merge(). If, however, the object you pass into merge() is detached, Hibernate creates a new object graph that is managed and it copies the state from your detached graph onto the new managed graph. Again, this is all dictated and governed by the JPA spec.
In terms of a generic strategy for "make sure this entity is managed, or make it managed", it kind of depends on if you want to account for not-yet-inserted data as well. Assuming you do, use something like
if ( session.contains( myEntity ) ) {
// nothing to do... myEntity is already associated with the session
}
else {
session.saveOrUpdate( myEntity );
}
Notice I used saveOrUpdate() rather than update(). If you do not want not-yet-inserted data handled here, use update() instead...

Entity states
JPA defines the following entity states:
New (Transient)
A newly created object that hasn’t ever been associated with a Hibernate Session (a.k.a Persistence Context) and is not mapped to any database table row is considered to be in the New (Transient) state.
To become persisted we need to either explicitly call the EntityManager#persist method or make use of the transitive persistence mechanism.
Persistent (Managed)
A persistent entity has been associated with a database table row and it’s being managed by the currently running Persistence Context. Any change made to such an entity is going to be detected and propagated to the database (during the Session flush-time).
With Hibernate, we no longer have to execute INSERT/UPDATE/DELETE statements. Hibernate employs a transactional write-behind working style and changes are synchronized at the very last responsible moment, during the current Session flush-time.
Detached
Once the currently running Persistence Context is closed all the previously managed entities become detached. Successive changes will no longer be tracked and no automatic database synchronization is going to happen.
Entity state transitions
You can change the entity state using various methods defined by the EntityManager interface.
To understand the JPA entity state transitions better, consider the following diagram:
When using JPA, to reassociate a detached entity to an active EntityManager, you can use the merge operation.
When using the native Hibernate API, apart from merge, you can reattach a detached entity to an active Hibernate Sessionusing the update methods, as demonstrated by the following diagram:
Merging a detached entity
The merge is going to copy the detached entity state (source) to a managed entity instance (destination).
Consider we have persisted the following Book entity, and now the entity is detached as the EntityManager that was used to persist the entity got closed:
Book _book = doInJPA(entityManager -> {
Book book = new Book()
.setIsbn("978-9730228236")
.setTitle("High-Performance Java Persistence")
.setAuthor("Vlad Mihalcea");
entityManager.persist(book);
return book;
});
While the entity is in the detached state, we modify it as follows:
_book.setTitle(
"High-Performance Java Persistence, 2nd edition"
);
Now, we want to propagate the changes to the database, so we can call the merge method:
doInJPA(entityManager -> {
Book book = entityManager.merge(_book);
LOGGER.info("Merging the Book entity");
assertFalse(book == _book);
});
And Hibernate is going to execute the following SQL statements:
SELECT
b.id,
b.author AS author2_0_,
b.isbn AS isbn3_0_,
b.title AS title4_0_
FROM
book b
WHERE
b.id = 1
-- Merging the Book entity
UPDATE
book
SET
author = 'Vlad Mihalcea',
isbn = '978-9730228236',
title = 'High-Performance Java Persistence, 2nd edition'
WHERE
id = 1
If the merging entity has no equivalent in the current EntityManager, a fresh entity snapshot will be fetched from the database.
Once there is a managed entity, JPA copies the state of the detached entity onto the one that is currently managed, and during the Persistence Context flush, an UPDATE will be generated if the dirty checking mechanism finds that the managed entity has changed.
So, when using merge, the detached object instance will continue to remain detached even after the merge operation.
Reattaching a detached entity
Hibernate, but not JPA supports reattaching through the update method.
A Hibernate Session can only associate one entity object for a given database row. This is because the Persistence Context acts as an in-memory cache (first level cache) and only one value (entity) is associated with a given key (entity type and database identifier).
An entity can be reattached only if there is no other JVM object (matching the same database row) already associated with the current Hibernate Session.
Considering we have persisted the Book entity and that we modified it when the Book entity was in the detached state:
Book _book = doInJPA(entityManager -> {
Book book = new Book()
.setIsbn("978-9730228236")
.setTitle("High-Performance Java Persistence")
.setAuthor("Vlad Mihalcea");
entityManager.persist(book);
return book;
});
_book.setTitle(
"High-Performance Java Persistence, 2nd edition"
);
We can reattach the detached entity like this:
doInJPA(entityManager -> {
Session session = entityManager.unwrap(Session.class);
session.update(_book);
LOGGER.info("Updating the Book entity");
});
And Hibernate will execute the following SQL statement:
-- Updating the Book entity
UPDATE
book
SET
author = 'Vlad Mihalcea',
isbn = '978-9730228236',
title = 'High-Performance Java Persistence, 2nd edition'
WHERE
id = 1
The update method requires you to unwrap the EntityManager to a Hibernate Session.
Unlike merge, the provided detached entity is going to be reassociated with the current Persistence Context and an UPDATE is scheduled during flush whether the entity has modified or not.
To prevent this, you can use the #SelectBeforeUpdate Hibernate annotation which will trigger a SELECT statement that fetched loaded state which is then used by the dirty checking mechanism.
#Entity(name = "Book")
#Table(name = "book")
#SelectBeforeUpdate
public class Book {
//Code omitted for brevity
}
Beware of the NonUniqueObjectException
One problem that can occur with update is if the Persistence Context already contains an entity reference with the same id and of the same type as in the following example:
Book _book = doInJPA(entityManager -> {
Book book = new Book()
.setIsbn("978-9730228236")
.setTitle("High-Performance Java Persistence")
.setAuthor("Vlad Mihalcea");
Session session = entityManager.unwrap(Session.class);
session.saveOrUpdate(book);
return book;
});
_book.setTitle(
"High-Performance Java Persistence, 2nd edition"
);
try {
doInJPA(entityManager -> {
Book book = entityManager.find(
Book.class,
_book.getId()
);
Session session = entityManager.unwrap(Session.class);
session.saveOrUpdate(_book);
});
} catch (NonUniqueObjectException e) {
LOGGER.error(
"The Persistence Context cannot hold " +
"two representations of the same entity",
e
);
}
Now, when executing the test case above, Hibernate is going to throw a NonUniqueObjectException because the second EntityManager already contains a Book entity with the same identifier as the one we pass to update, and the Persistence Context cannot hold two representations of the same entity.
org.hibernate.NonUniqueObjectException:
A different object with the same identifier value was already associated with the session : [com.vladmihalcea.book.hpjp.hibernate.pc.Book#1]
at org.hibernate.engine.internal.StatefulPersistenceContext.checkUniqueness(StatefulPersistenceContext.java:651)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performUpdate(DefaultSaveOrUpdateEventListener.java:284)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsDetached(DefaultSaveOrUpdateEventListener.java:227)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:92)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:73)
at org.hibernate.internal.SessionImpl.fireSaveOrUpdate(SessionImpl.java:682)
at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:674)
Conclusion
The merge method is to be preferred if you are using optimistic locking as it allows you to prevent lost updates.
The update is good for batch updates as it can prevent the additional SELECT statement generated by the merge operation, therefore reducing the batch update execution time.

Undiplomatic answer: You're probably looking for an extended persistence context. This is one of the main reasons behind the Seam Framework... If you're struggling to use Hibernate in Spring in particular, check out this piece of Seam's docs.
Diplomatic answer: This is described in the Hibernate docs. If you need more clarification, have a look at Section 9.3.2 of Java Persistence with Hibernate called "Working with Detached Objects." I'd strongly recommend you get this book if you're doing anything more than CRUD with Hibernate.

If you are sure that your entity has not been modified (or if you agree any modification will be lost), then you may reattach it to the session with lock.
session.lock(entity, LockMode.NONE);
It will lock nothing, but it will get the entity from the session cache or (if not found there) read it from the DB.
It's very useful to prevent LazyInitException when you are navigating relations from an "old" (from the HttpSession for example) entities. You first "re-attach" the entity.
Using get may also work, except when you get inheritance mapped (which will already throw an exception on the getId()).
entity = session.get(entity.getClass(), entity.getId());

I went back to the JavaDoc for org.hibernate.Session and found the following:
Transient instances may be made persistent by calling save(), persist() or
saveOrUpdate(). Persistent instances may be made transient by calling delete(). Any instance returned by a get() or load() method is persistent. Detached instances may be made persistent by calling update(), saveOrUpdate(), lock() or replicate(). The state of a transient or detached instance may also be made persistent as a new persistent instance by calling merge().
Thus update(), saveOrUpdate(), lock(), replicate() and merge() are the candidate options.
update(): Will throw an exception if there is a persistent instance with the same identifier.
saveOrUpdate(): Either save or update
lock(): Deprecated
replicate(): Persist the state of the given detached instance, reusing the current identifier value.
merge(): Returns a persistent object with the same identifier. The given instance does not become associated with the session.
Hence, lock() should not be used straightway and based on the functional requirement one or more of them can be chosen.

I did it that way in C# with NHibernate, but it should work the same way in Java:
public virtual void Attach()
{
if (!HibernateSessionManager.Instance.GetSession().Contains(this))
{
ISession session = HibernateSessionManager.Instance.GetSession();
using (ITransaction t = session.BeginTransaction())
{
session.Lock(this, NHibernate.LockMode.None);
t.Commit();
}
}
}
First Lock was called on every object because Contains was always false. The problem is that NHibernate compares objects by database id and type. Contains uses the equals method, which compares by reference if it's not overwritten. With that equals method it works without any Exceptions:
public override bool Equals(object obj)
{
if (this == obj) {
return true;
}
if (GetType() != obj.GetType()) {
return false;
}
if (Id != ((BaseObject)obj).Id)
{
return false;
}
return true;
}

Session.contains(Object obj) checks the reference and will not detect a different instance that represents the same row and is already attached to it.
Here my generic solution for Entities with an identifier property.
public static void update(final Session session, final Object entity)
{
// if the given instance is in session, nothing to do
if (session.contains(entity))
return;
// check if there is already a different attached instance representing the same row
final ClassMetadata classMetadata = session.getSessionFactory().getClassMetadata(entity.getClass());
final Serializable identifier = classMetadata.getIdentifier(entity, (SessionImplementor) session);
final Object sessionEntity = session.load(entity.getClass(), identifier);
// override changes, last call to update wins
if (sessionEntity != null)
session.evict(sessionEntity);
session.update(entity);
}
This is one of the few aspects of .Net EntityFramework I like, the different attach options regarding changed entities and their properties.

I came up with a solution to "refresh" an object from the persistence store that will account for other objects which may already be attached to the session:
public void refreshDetached(T entity, Long id)
{
// Check for any OTHER instances already attached to the session since
// refresh will not work if there are any.
T attached = (T) session.load(getPersistentClass(), id);
if (attached != entity)
{
session.evict(attached);
session.lock(entity, LockMode.NONE);
}
session.refresh(entity);
}

Sorry, cannot seem to add comments (yet?).
Using Hibernate 3.5.0-Final
Whereas the Session#lock method this deprecated, the javadoc does suggest using Session#buildLockRequest(LockOptions)#lock(entity)and if you make sure your associations have cascade=lock, the lazy-loading isn't an issue either.
So, my attach method looks a bit like
MyEntity attach(MyEntity entity) {
if(getSession().contains(entity)) return entity;
getSession().buildLockRequest(LockOptions.NONE).lock(entity);
return entity;
Initial tests suggest it works a treat.

Perhaps it behaves slightly different on Eclipselink. To re-attach detached objects without getting stale data, I usually do:
Object obj = em.find(obj.getClass(), id);
and as an optional a second step (to get caches invalidated):
em.refresh(obj)

try getHibernateTemplate().replicate(entity,ReplicationMode.LATEST_VERSION)

In the original post, there are two methods, update(obj) and merge(obj) that are mentioned to work, but in opposite circumstances. If this is really true, then why not test to see if the object is already in the session first, and then call update(obj) if it is, otherwise call merge(obj).
The test for existence in the session is session.contains(obj). Therefore, I would think the following pseudo-code would work:
if (session.contains(obj))
{
session.update(obj);
}
else
{
session.merge(obj);
}

to reattach this object, you must use merge();
this methode accept in parameter your entity detached and return an entity will be attached and reloaded from Database.
Example :
Lot objAttach = em.merge(oldObjDetached);
objAttach.setEtat(...);
em.persist(objAttach);

calling first merge() (to update persistent instance), then lock(LockMode.NONE) (to attach the current instance, not the one returned by merge()) seems to work for some use cases.

Property hibernate.allow_refresh_detached_entity did the trick for me. But it is a general rule, so it is not very suitable if you want to do it only in some cases. I hope it helps.
Tested on Hibernate 5.4.9
SessionFactoryOptionsBuilder

try getHibernateTemplate().saveOrUpdate()

Detach an entity from JPA/EJB3 persistence context

What would be the easiest way to detach a specific JPA Entity Bean that was acquired through an EntityManager. Alternatively, could I have a query return detached objects in the first place so they would essentially act as 'read only'?
The reason why I want to do this is becuase I want to modify the data within the bean - with in my application only, but not ever have it persisted to the database. In my program, I eventually have to call flush() on the EntityManager, which would persist all changes from attached entities to the underyling database, but I want to exclude specific objects.

(may be too late to answer, but can be useful for others)
I'm developing my first system with JPA right now. Unfortunately I'm faced with this problem when this system is almost complete.
Simply put. Use Hibernate, or wait for JPA 2.0.
In Hibernate, you can use 'session.evict(object)' to remove one object from session. In JPA 2.0, in draft right now, there is the 'EntityManager.detach(object)' method to detach one object from persistence context.

No matter which JPA implementation you use, Just use entityManager.detach(object) it's now in JPA 2.0 and part of JEE6.

If you need to detach an object from the EntityManager and you are using Hibernate as your underlying ORM layer you can get access to the Hibernate Session object and use the Session.evict(Object) method that Mauricio Kanada mentioned above.
public void detach(Object entity) {
org.hibernate.Session session = (Session) entityManager.getDelegate();
session.evict(entity);
}
Of course this would break if you switched to another ORM provider but I think this is preferably to trying to make a deep copy.

Unfortunately, there's no way to disconnect one object from the entity manager in the current JPA implementation, AFAIR.
EntityManager.clear() will disconnect all the JPA objects, so that might not be an appropriate solution in all the cases, if you have other objects you do plan to keep connected.
So your best bet would be to clone the objects and pass the clones to the code that changes the objects. Since primitive and immutable object fields are taken care of by the default cloning mechanism in a proper way, you won't have to write a lot of plumbing code (apart from deep cloning any aggregated structures you might have).

As far as I know, the only direct ways to do it are:
Commit the txn - Probably not a reasonable option
Clear the Persistence Context - EntityManager.clear() - This is brutal, but would clear it out
Copy the object - Most of the time your JPA objects are serializable, so this should be easy (if not particularly efficient).

If using EclipseLink you also have the options,
Use the Query hint, eclipselink.maintain-cache"="false - all returned objects will be detached.
Use the EclipseLink JpaEntityManager copy() API to copy the object to the desired depth.

If there aren't too many properties in the bean, you might just create a new instance and set all of its properties manually from the persisted bean.
This could be implemented as a copy constructor, for example:
public Thing(Thing oldBean) {
this.setPropertyOne(oldBean.getPropertyOne());
// and so on
}
Then:
Thing newBean = new Thing(oldBean);

this is quick and dirty, but you can also serialize and deserialize the object.

Since I am using SEAM and JPA 1.0 and my system has a fuctinality that needs to log all fields changes, i have created an value object or data transfer object if same fields of the entity that needs to be logged. The constructor of the new pojo is:
public DocumentoAntigoDTO(Documento documentoAtual) {
Method[] metodosDocumento = Documento.class.getMethods();
for(Method metodo:metodosDocumento){
if(metodo.getName().contains("get")){
try {
Object resultadoInvoke = metodo.invoke(documentoAtual,null);
Method[] metodosDocumentoAntigo = DocumentoAntigoDTO.class.getMethods();
for(Method metodoAntigo : metodosDocumentoAntigo){
String metodSetName = "set" + metodo.getName().substring(3);
if(metodoAntigo.getName().equals(metodSetName)){
metodoAntigo.invoke(this, resultadoInvoke);
}
}
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
}
}
}

In JPA 1.0 (tested using EclipseLink) you could retrieve the entity outside of a transaction. For example, with container managed transactions you could do:
public MyEntity myMethod(long id) {
final MyEntity myEntity = retrieve(id);
// myEntity is detached here
}
#TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
public MyEntity retrieve(long id) {
return entityManager.find(MyEntity.class, id);
}

Do deal with a similar case I have created a DTO object that extends the persistent entity object as follows:
class MyEntity
{
public static class MyEntityDO extends MyEntity {}
}
Finally, an scalar query will retrieve the desired non managed attributes:
(Hibernate) select p.id, p.name from MyEntity P
(JPA) select new MyEntity(p.id, p.name) from myEntity P

If you get here because you actually want to pass an entity across a remote boundary then you just put some code in to fool the hibernazi.
for(RssItem i : result.getChannel().getItem()){
}
Cloneable wont work because it actually copies the PersistantBag across.
And forget about using serializable and bytearray streams and piped streams. creating threads to avoid deadlocks kills the entire concept.

I think there is a way to evict a single entity from EntityManager by calling this
EntityManagerFactory emf;
emf.getCache().evict(Entity);
This will remove particular entity from cache.

Im using entityManager.detach(returnObject);
which worked for me.

I think you can also use method EntityManager.refresh(Object o) if primary key of the entity has not been changed. This method will restore original state of the entity.