Bug 357153

Comment 1 Christoph Laeubrich 2011-09-08 15:45:56 EDT

Created attachment 203028 [details]
Testcase for problem

Includes:
 - Annotated file and persistence.xml
 - testcase bundle (source included as well)

Comment 2 Christoph Laeubrich 2011-09-08 15:47:17 EDT

Comment on attachment 203028 [details]
Testcase for problem

Base class for example

@MappedSuperclass
public class PersitentBase {
    @Version
    private long    version;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long    id;

    @Transient
    private boolean incremented;

    /**
     * @return the current value of id
     */
    public long getID() {
        return id;
    }

    /**
     * @return the current value of version
     */
    public long getVersion() {
        return version;
    }

    /* (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "PersitentBase [version=" + version + ", id=" + id + "]";
    }

    /**
     * 
     */
    public void incrementVersion() {
        if (!incremented) {
            version++;
            incremented = true;
        }
    }
}

Comment 3 Tom Ware 2011-09-08 15:56:31 EDT

The reason you are seeing this issue is that you are doing a primary key lookup.  In the default case, this will return an object from the cache.

You have numerous options.

- You can do a refresh
- You can use a refresh query hint
- There are a number of cache configuration options that will alleviate this issue depending on your goal (cache type and size, isolated cache etc.)

Comment 4 Christoph Laeubrich 2011-09-08 16:13:13 EDT

(In reply to comment #3)
Hi Tom,

thank for your comment.

> The reason you are seeing this issue is that you are doing a primary key
> lookup.  In the default case, this will return an object from the cache.
I'm a little bit confused. Since I'm closing the EntityManager shouldn't it assume that all chached entries are invalidated?

> You have numerous options.
> - You can do a refresh
Calling refresh on the object throws an exception since the object is detached. Selecting the object (and thus reattaching it) and the calling refresh works, but this don't feels right.

> - You can use a refresh query hint
Is this possible in a portable way or do I need to use EclipseLink specific Annotations?

> - There are a number of cache configuration options that will alleviate this
> issue depending on your goal (cache type and size, isolated cache etc.)
My goal is the following:
Many distributed clients loading objects and holding a local (detached) copy. Everytime the user tries to edit the Object is reloaded from the database and the saved (which failed if another client has edited this object because of incremented version number)


Is this the intended behaviour that detached objects are still fetched from the cache? Sounds confusing to me or do i get something wrong?

Comment 5 Tom Ware 2011-09-08 16:23:10 EDT

> The reason you are seeing this issue is that you are doing a primary key
> lookup.  In the default case, this will return an object from the cache.
I'm a little bit confused. Since I'm closing the EntityManager shouldn't it
assume that all chached entries are invalidated?

- There is a 2nd level cache.  It is, for all intents and purposes, on the EntityManagerFactory.  This is where you are getting the object from.

> You have numerous options.
> - You can do a refresh
Calling refresh on the object throws an exception since the object is detached.
Selecting the object (and thus reattaching it) and the calling refresh works,
but this don't feels right.

- try the refresh query hint.  It can either be provided as a hint for your JPQL or Criteria Query, or in the optional list of properties in the find method:

http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_%28ELUG%29#Refresh


> - You can use a refresh query hint
Is this possible in a portable way or do I need to use EclipseLink specific
Annotations?

- Query hints are in the JPA spec and complete portable - see above for details about EclipseLink's refresh hint.

> - There are a number of cache configuration options that will alleviate this
> issue depending on your goal (cache type and size, isolated cache etc.)
My goal is the following:
Many distributed clients loading objects and holding a local (detached) copy.
Everytime the user tries to edit the Object is reloaded from the database and
the saved (which failed if another client has edited this object because of
incremented version number)


Is this the intended behaviour that detached objects are still fetched from the
cache? Sounds confusing to me or do i get something wrong?

- That is the goal of refresh.  The cache provides quite alot of performance benefit when reading and when tied with a good locking policy is very powerful. If, however, you would like you cache tied more closely to your EntityManager - rather than your EntityManagerFactory, you can use our isolated cache setting.

Take a look at this: 

http://wiki.eclipse.org/Using_EclipseLink_JPA_Extensions_%28ELUG%29#Using_EclipseLink_JPA_Extensions_for_Entity_Caching

The entry on: "eclipselink.cache.shared.default" is a good start.

Comment 6 Christoph Laeubrich 2011-09-08 16:36:31 EDT

(In reply to comment #5)
Hi Tom,

thanks for your explanation I was not aware that the cache was bound to the EMF and not to the EM, sorry for the inconvenience opening this issue :)

I found out that with JPA 2.0 

 @Cacheable(false)

annotation the caching could be switched of thanks for taking my head in the right direction, I think this will work for me until I have understand the whole cache configuration thing :)

Comment 7 Eclipse Webmaster 2022-06-09 10:16:39 EDT

The Eclipselink project has moved to Github: https://github.com/eclipse-ee4j/eclipselink

Comment 8 Eclipse Webmaster 2022-06-09 10:32:36 EDT

The Eclipselink project has moved to Github: https://github.com/eclipse-ee4j/eclipselink