I would like to use JPA2 Criteria API with metamodel objects, which seems to be pretty easy:
...
Root<JPAAlbum> albm = cq.from(JPAAlbum.class);
... albm.get(JPAAlbum_.theme) ... ;
but this Root.get always throws a NullPointerException
. JPAAlbum_.theme
was automatically generated by Hibernate and looks like
public static volatile SingularAttribute<JPAAlbum, JPATheme> theme;
but it's obviously never populated.
Am I missing a step in the initialization of the framework ?
EDIT: here is a snippet of how I use JPA and the metamodel when it's crashing:
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<JPAAlbum> cq = cb.createQuery(JPAAlbum.class) ;
Root<JPAAlbum> albm = cq.from(JPAAlbum.class);
cq.where(cb.equal(albm.get(JPAAlbum_.theme).get(JPATheme_.id),
session.getTheme().getId())) ;
(JPAAlbum_
is a class, so I just import
before) and the associated stacktrace:
Caused by: java.lang.NullPointerException
at org.hibernate.ejb.criteria.path.AbstractPathImpl.get(AbstractPathImpl.java:138)
at net.wazari.dao.jpa.WebAlbumsDAOBean.getRestrictionToAlbumsAllowed(WebAlbumsDAOBean.java:55)
EDIT 2:
In the JBoss EntityManager guide, I can see that
When the Hibernate EntityManagerFactory is being built, it will look for a canonical metamodel class for each of the managed typed is knows about and if it finds any it will inject the appropriate metamodel information into them, as outlined in [JPA 2 Specification, section 6.2.2, pg 200]
I could also verify with
for (ManagedType o : em.getMetamodel().getManagedTypes()) {
log.warn("___") ;
for (Object p : o.getAttributes()) {
log.warn(((Attribute)p).getName()) ;
}
}
that Hibernate is aware of my metamodel, the attribute names are written, however
log.warn("_+_"+JPAPhoto_.id+"_+_") ;
remains desperately empty ...
EDIT3: here is the JPAAlbum entity and its metamodel class.
What else can I tell about my configuration ...
I use Hibernat 3.5.6-Final (according to META-INF/MANIFEST.MF),
deploy on Glassfish 3.0.1
from Netbeans 6.9.1;
and the application relies on EJB 3.1,
I hope it will help !
EDIT 4:
unfortunately, the JUnit test leads to the same exception:
java.lang.NullPointerException
at org.hibernate.ejb.criteria.path.AbstractPathImpl.get(AbstractPathImpl.java:138)
at net.wazari.dao.test.TestMetaModel.foo(TestMetaModel.java:55)
A much simpler project is available here/tarball. It only contains my entities and their metamodel, plus a JUnit test (foo crashes with metamodel, bar is okay with the usual Query.
EDIT 5:
You should be able to reproduce the problem by downloading the tarball, building the project:
ant compile
or
ant dist
and start the JUnit test net.wazari.dao.test.TestMetaModel
CLASSPATH=`sh runTest.sh` java org.junit.runner.JUnitCore net.wazari.dao.test.TestMetaModel
(edit runTest.sh
to point CLASSPATH to the right location of your JUnit4-5 jar)
All the hibernate dependencies I use should be included in the archive.
I had the same issue and it was fixed by putting the Model
and Model_
class into the same package.