GWT doesn´t find my persistence.xml - gwt

Question

I´m trying to save a simple user in my jpa hibernate db.
So I have a persistence.xml that I know that works (If I execute a simple test without deploying the gwt app).
The problem is that when I test it with my user interface, the persist method throw me the next error: (I think this is cause Doesn´t find the persistence.xml)
[ERROR] javax.persistence.PersistenceException: [PersistenceUnit: isw2.tasks] Unable to >configure EntityManagerFactory
... bla bla bla
[ERROR] Caused by: org.hibernate.HibernateException: Unable to get the default Bean >Validation factory
... more bla bla bla..
[ERROR] Caused by: java.lang.reflect.InvocationTargetException
...
[ERROR] Caused by: org.hibernate.HibernateException: Unable to build the default ValidatorFactory
[ERROR] at org.hibernate.cfg.beanvalidation.TypeSafeActivator.getValidatorFactory(TypeSafeActivator.java:383)
[ERROR] at org.hibernate.cfg.beanvalidation.TypeSafeActivator.applyDDL(TypeSafeActivator.java:109)
.....
[ERROR] Caused by: javax.validation.ValidationException: Unable to find a default provider
[ERROR] at javax.validation.Validation$GenericBootstrapImpl.configure(Validation.java:264)
[ERROR] at javax.validation.Validation.buildDefaultValidatorFactory(Validation.java:111)
[ERROR] at org.hibernate.cfg.beanvalidation.TypeSafeActivator.getValidatorFactory(TypeSafeActivator.ja
This is the method I know that works:
`EntityManagerFactory emf = Persistence
.createEntityManagerFactory("isw2.tasks");
em = emf.createEntityManager();
em.getTransaction().begin();
em.persist(u);
em.getTransaction().commit();
em.clear();
em.close();
`
And the most usefull for us, my proyect skeleton: (See that the persistence.xml file is there!)
I´m using maven and deploying the web app with the codehaus plugin.
Thanks in advance experts ;)

Answer 1

The exception message Unable to find a default provider suggests that hibernate cannot find a validation provider.
Is your Hibernate Validator jar on your runtime classpath? Also do note that you need to use Hibernate Validator 4 or later.