Re: EMF JNDI lookup is starting openJPA every time - was: Howto integrate JPA within EJB2.1 session beans?

Craig L Russell Tue, 27 Feb 2007 15:32:46 -0800

We had a similar issue with the JDO Reference Implementation. What we ended up with was implementing the naming.Referenceable interface and writing our own externalization protocols that basically allowed the container to create new instances of our Factory that were actually trivial wrappers that delegated to the real Factory.

So yes, I believe that unless a container "knows" that a bound value is actually sharable (see below), it will generally serialize the instance and then deserialize it for each caller. The way to make this operation perform well (short of telling the container to share it) is to implement the Referenceable contracts.

I can drag out more details if there is interest. Or you can look at the implementation of FOStorePMF in the Apache JDO project.


Craig

On Feb 27, 2007, at 9:47 AM, Pinaki Poddar wrote:

But maybe something funky is happening with JNDI serializing the factory and then deserializing it or something.

From J2EE 1.4 spec, page 59 (J2EE.5.2 Java Naming and Directory Interface:

In general, lookups of objects in the JNDI java: namespace are required to return a new instance of the requested object every time. Exceptions are

allowed for the following:

- The container knows the object is immutable (for example, objects of type java.lang.String), or knows that the application can't change the state of

the object.

-The object is defined to be a singleton, such that only one instance of the object may exist in the JVM. -The name used for the lookup is defined to return an instance of the object that might be shared. The name java:comp/ORB is such a name.

In these cases, a shared instance of the object may be returned. In all other cases, a new instance of the requested object must be returned on each

lookup.


Pinaki Poddar
BEA Systems
415.402.7317


-----Original Message-----
From: Patrick Linskey [mailto:[EMAIL PROTECTED]
Sent: Monday, February 26, 2007 11:11 PM
To: open-jpa-dev@incubator.apache.org

Subject: RE: EMF JNDI lookup is starting openJPA every time - was: Howto integrate JPA within EJB2.1 session beans?


It should be going through the following code:

public static OpenJPAEntityManagerFactory createEntityManagerFactory

        (String jndiLocation, Context context) {
        if (jndiLocation == null)
            throw new NullPointerException("jndiLocation == null");

        try {
            if (context == null)
                context = new InitialContext();

            Object o = context.lookup(jndiLocation);

return (OpenJPAEntityManagerFactory) PortableRemoteObject.narrow(o,

                OpenJPAEntityManagerFactory.class);
        } catch (NamingException ne) {
            throw new ArgumentException(_loc.get("naming-exception",
                jndiLocation), new Throwable[]{ ne }, null, true);
        }
    }

I don't see anything in there that would be causing a creation to happen. But maybe something funky is happening with JNDI serializing the factory and then deserializing it or something.

Do you have any means of getting a stack from where the creation is happening? It'd be great to get a bit more context about what's going on.


-Patrick

--
Patrick Linskey
BEA Systems, Inc.

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-----Original Message-----
From: Hans J. Prueller [mailto:[EMAIL PROTECTED]
Sent: Saturday, February 24, 2007 10:36 PM
To: open-jpa-dev@incubator.apache.org
Subject: EMF JNDI lookup is starting openJPA every time -
was: Howto integrate JPA within EJB2.1 session beans?

Hi together, Patrick,

the code you suggested for doing a helper method that deals with the
EMF JNDI lookup and the EM creating within our J2EE1.4 app basically
works fine, but as you perhaps may remember I asked why the method is
called "create":

EntityManagerFactory myemf =
OpenJPAPersistence.createEntityManagerFactory(strJNDILocation,
(Context)null);

It seems that the method above really creates a NEW EMF on every
invocation!
I checked the logs of my application and I see the following messages
on every invocation of my PersistenceService.getEntityManger()
method (which
does the above lookup and some more ..)

2007-02-25 07:27:05,687 : PersistenceService.getEntityManager
: creating a
fresh
, clean EntityManager from JNDI EMF.
15  lbsims  INFO   [RMI TCP Connection(35)-192.168.0.5]
openjpa.Runtime -
Starti
ng OpenJPA 0.9.7-incubating-SNAPSHOT
15  lbsims  INFO   [RMI TCP Connection(35)-192.168.0.5]
openjpa.jdbc.JDBC -
Open

JPA will now connect to the database to attempt to determine what type

of databa se dictionary to use.  To prevent this connection in the
future, set your openjp a.jdbc.DBDictionary configuration property to
the appropriate value for your dat abase (see the documentation for
available values).
15  lbsims  INFO   [RMI TCP Connection(35)-192.168.0.5]
openjpa.jdbc.JDBC -
Usin
g dictionary class
"org.apache.openjpa.jdbc.sql.MySQLDictionary" (MySQL 5.0.27-c
ommunity-nt ,MySQL-AB JDBC Driver mysql-connector-java-5.0.4 ( $Date:
2006-10-19
 17:47:48 +0200 (Thu, 19 Oct 2006) $, $Revision: 5908 $ )).
15  lbsims  INFO   [RMI TCP Connection(35)-192.168.0.5]
openjpa.MetaData -
Found
 1 classes with metadata in 0 milliseconds.

It seems that OpenJPA is now bootstrapping everytime I access it. I am

binding the EMF somewhen at bootstrapping time with

final EntityManagerFactory emFactory = Persistence
                                .createEntityManagerFactory("lbsims");

Context ictx = new InitialContext();
ictx.bind(PersistenceService.EMF_JNDI_LOCATION, emFactory);

The lookup uses the same constants, so the EMF in JNDI should be
found?

EntityManagerFactory emf = OpenJPAPersistence
        
.createEntityManagerFactory(EMF_JNDI_LOCATION, (Context) null);

Any Idea what could be wrong here?

regards,
HANS

-----Ursprüngliche Nachricht-----
Von: Patrick Linskey [mailto:[EMAIL PROTECTED]
Gesendet: Freitag, 23. Februar 2007 18:46
An: open-jpa-dev@incubator.apache.org
Betreff: RE: TYPO? Howto integrate JPA within EJB2.1 session beans?
[architecture]

Typo indeed. It should be

OpenJPAPersistence.toBrokerFactory(emf). Sorry

about that.

-Patrick

--
Patrick Linskey
BEA Systems, Inc.

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-----Original Message-----
From: Hans J. Prueller [mailto:[EMAIL PROTECTED]
Sent: Friday, February 23, 2007 9:43 AM
To: open-jpa-dev@incubator.apache.org
Subject: RE: TYPO? Howto integrate JPA within EJB2.1 session
beans? [architecture]

Patrick,

I'm currently trying your tip with a PersistenceService util class
doing the lookup of a synchronized entity manager. The problem is
that your sample code does not work!

in fact the statement

final BrokerFactory bf = OpenJPAPersistence.cast(emf);

is the problem. the above "cast" does not return a BrokerFactory
instance!

I am using a 2 days old nightly snapshot 0.9.7 build

Where is the problem?

Hans

-----Ursprüngliche Nachricht-----
Von: Patrick Linskey [mailto:[EMAIL PROTECTED]
Gesendet: Donnerstag, 22. Februar 2007 23:22
An: open-jpa-dev@incubator.apache.org
Betreff: RE: RE: Howto integrate JPA within EJB2.1

session beans?

[architecture]

Unfortunately, that means that we're using a synchronized
block during the lookup. If it looks like EM lookup is a
scalability issue for your app, do let us know -- it would be
pretty straightforward to replace the synchronized block with
a concurrent map.


OK, I got fed up with that synchronized block. OPENJPA-161

tracks the

issue; I've got a patch that I'll submit once some more

eyes look at it.


-Patrick

--
Patrick Linskey
BEA Systems, Inc.

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-----Original Message-----
From: Patrick Linskey [mailto:[EMAIL PROTECTED]
Sent: Thursday, February 22, 2007 8:38 AM
To: open-jpa-dev@incubator.apache.org
Subject: RE: RE: Howto integrate JPA within EJB2.1 session
beans? [architecture]

If I understand it correct, I "just" have to bind the EMF
onserver startup like.

context.bind("my/jndi/name/for/emf",myEMFVariable);


Yep.

        //does the statement below again create a NEW EMF

or ist this

        //just a lookup in the jndi-tree? but why is it
called "Create"
        //and not get?
        EntityManagerFactory emf = OpenJPAPersistence
            .createEntityManagerFactory(
                "your/EMF/JNDI/location", (Context) null);


It's just a lookup. I'm not sure why it's called

'create'. Anyone?

        //why do I have to create a new

broker/entitymanager this way?

        //is this because I have to "synchronize" the SLSBs
transaction
        //context with the newly created entitymanager?


Yes -- our current OpenJPAPersistence EM lookup methods

all create new

EMs. The broker code will look up one associated with

the current

transaction, which is what you're looking for.

Unfortunately, that means that we're using a synchronized

block during

the lookup. If it looks like EM lookup is a scalability

issue for your

app, do let us know -- it would be pretty straightforward to
replace the synchronized block with a concurrent map.

So if understand that right I just would have to call

PersistenceService.getEntitymanager();

in every SLSB method (NOT in ejbCreate) when needed? fine.


Yep.

I really appreciate your help - it's quite complex

to integrate

JPA into an existing Java2EE 1.4 AppServer

environment.. *puh*


Yes -- sorry about that. We should at least be creating
better-designed helper methods in OpenJPA to help out with
this.

One alternative, of course, is to use Spring 2, which does a
pretty good job of JPA bootstrapping.

-Patrick

--
Patrick Linskey
BEA Systems, Inc.

______________________________________________________________
_________
Notice:  This email message, together with any attachments,
may contain information  of  BEA Systems,  Inc.,  its
subsidiaries  and affiliated entities,  that may be
confidential,  proprietary, copyrighted  and/or legally
privileged, and is intended solely for the use of the
individual or entity named in this message. If you are not the
intended recipient, and have received this message in error,
please immediately return this by email and then delete it.

-----Original Message-----
From: Hans Prueller [mailto:[EMAIL PROTECTED]
Sent: Thursday, February 22, 2007 4:36 AM
To: open-jpa-dev@incubator.apache.org;
open-jpa-dev@incubator.apache.org
Subject: Re: RE: Howto integrate JPA within EJB2.1 session
beans? [architecture]

Patrick,

thank you for that tip. To be true, I was not aware of
lifecycle related problems between my SLSBs and JPA - thank
you for that hint. As I want to avoid working with
ThreadLocal (simply because I didn't work with ThreadLocals
yet) I would prefer the JNDI-EMF based approach.

If I understand it correct, I "just" have to bind the EMF
onserver startup like.

context.bind("my/jndi/name/for/emf",myEMFVariable);

I would be interested what the code for the
PersistenceService class does:

        //does the statement below again create a NEW EMF

or ist this

        //just a lookup in the jndi-tree? but why is it
called "Create"
        //and not get?
        EntityManagerFactory emf = OpenJPAPersistence
            .createEntityManagerFactory(
                "your/EMF/JNDI/location", (Context) null);

        //why do i have to cast the EMF to a

brokerfactory now? I

        //would guess the "broker" is something like a

more abstract

        //concept of entitymanager(factory)?

        //why do I have to create a new

broker/entitymanager this way?

        //is this because I have to "synchronize" the SLSBs
transaction
        //context with the newly created entitymanager?

        BrokerFactory bf = OpenJPAPersistence.cast(emf);
        Broker b = bf.newBroker(
        bf.getConfiguration().getConnectionUserName(),
          bf.getConfiguration().getConnectionPassword(),
          true, // the broker is part of a JTA managed tx

bf.getConfiguration().getConnectionRetainModeConstant(),

          true); // look for an existing Broker on the tx

        broker.setAutoDetach(AutoDetach.DETACH_CLOSE, true);

broker.setAutoDetach(AutoDetach.DETACH_ROLLBACK, true);

        broker.setDetachedNew(false);

        return OpenJPAPersistence.toEntityManager(b);
    }

So if understand that right I just would have to call

PersistenceService.getEntitymanager();

in every SLSB method (NOT in ejbCreate) when needed? fine. I
really appreciate your help - it's quite complex to

integrate

JPA into an existing Java2EE 1.4 AppServer

environment.. *puh*


regards
Hans

-------- Original-Nachricht --------
Datum: Wed, 21 Feb 2007 08:43:20 -0800
Von: "Patrick Linskey" <[EMAIL PROTECTED]>
An: open-jpa-dev@incubator.apache.org
CC:
Betreff: RE: Howto integrate JPA within EJB2.1

session beans?

[architecture]

Another common technique is to get an EMF into

JNDI, either

by using a

startup hook or deploying OpenJPA as a JCA RAR.

Are you looking to integrate OpenJPA with your

current managed

transaction? If so, I'd be careful about creating an EM in

ejbCreate(),

as its lifecycle is related to the life of the SLSB,

not to the

transactional context (the SLSB might be pooled). So, I'd

just try to

get the EMF into JNDI when the server starts

(creating EMFs

is slow).

Then, you could avoid having to use your own ThreadLocal

work by using

the internal OpenJPA BrokerFactory APIs:

public class PersistenceService {
    public static EntityManager getEntityManager() {
        EntityManagerFactory emf = OpenJPAPersistence
            .createEntityManagerFactory(
                "your/EMF/JNDI/location", (Context) null);
        BrokerFactory bf = OpenJPAPersistence.cast(emf);
        Broker b = bf.newBroker(
            bf.getConfiguration().getConnectionUserName(),
            bf.getConfiguration().getConnectionPassword(),
            true, // the broker is part of a JTA

managed tx

bf.getConfiguration().getConnectionRetainModeConstant(),

            true); // look for an existing Broker

on the tx


        // do some JPA configuration setup. Logic

stolen from

        // EntityManagerFactoryImpl.

broker.setAutoDetach(AutoDetach.DETACH_CLOSE, true);

broker.setAutoDetach(AutoDetach.DETACH_ROLLBACK, true);

        broker.setDetachedNew(false);

        return OpenJPAPersistence.toEntityManager(b);
    }
}

Meanwhile, we really should add a couple new

OpenJPAPersistence /

OpenJPAEntityManagerFactory methods to help out with

this type of

bootstrapping.

-Patrick

--
Patrick Linskey
BEA Systems, Inc.

______________________________________________________________

_________

Notice:  This email message, together with any

attachments,

may contain

information  of  BEA Systems,  Inc.,  its

subsidiaries  and

 affiliated

entities,  that may be confidential,  proprietary,

copyrighted  and/or

legally privileged, and is intended solely for the use of

the individual

or entity named in this message. If you are not the

intended recipient,

and have received this message in error, please

immediately

return this

by email and then delete it.

-----Original Message-----
From: Hans Prueller [mailto:[EMAIL PROTECTED]
Sent: Wednesday, February 21, 2007 1:02 AM
To: open-jpa-dev@incubator.apache.org
Subject: Howto integrate JPA within EJB2.1

session beans?

[architecture]

Hi together,

I'm sorry for bothering you with numerous basic

questions

regarding OpenJPA and its usage but I have to migrate
existing CMP EJBs to migrate within short time

to OpenJPA as

we're having stability issues with the current

CMP engine.


One last question I'd like to ask is regarding the
recommended architecture of using OpenJPA within EJB2.1
Stateless sessino beans:

I need to work with persistence i.e. the EntityManager
throughout all the session beans methods so my

idea is to:


- create a EntityManagerFactory in the

ejbCreate() method

of the SLSB

- and also create the EntityManager itself in the
ejbCreeate() method and store it as a member variable

of the SLSB

- this would allow easy access within the SB's

methods by

just using the already initialized entity

manager varialbe

em.createNamedQuery() .. etc. etc.
- clean up should be performed in the ejbRemove() method

of the SLSB


I think doing so will allow migratino to

openJPA with less

work than doing the whole lookup procedure in

every method

separately.

what do you think? are there any pitfalls i've

overlooked?


thank you for your ideas!

regards
Hans
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Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!

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Re: EMF JNDI lookup is starting openJPA every time - was: Howto integrate JPA within EJB2.1 session beans?

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