Hi All,
I'm fairly new to GWT and attempting to use GWT with JPA 2.0 , but
have come across various problems. I'm using the setup below:
* Entity classes with annotations in a JAR on the GWT app classpath
* JPA controllers (largely generated classes that perform the actual
JPA actions, such as persisting objects to the database) in the same
JAR as the entity classes.
* GWT RPC calls (the server side accesses the JPA controllers)
I'm using Eclipse as my IDE with the GWT plugin.
A couple of questions:
* Can the development mode server (Jetty I believe) support JPA? (all
the relevant libraries are on the GWT project's classpath, so there
are no compile errors) Or do I need to use an external server, and if
so what type would be appropriate?
* How do I structure the files, e.g. where do I put persistence.xml?
Do I keep it with the entity classes from the other project or do I
need it to be with the GWT project?
The following things are working fine so far:
* RPC calls
* Creating an instance of an entity class
* Creating an instance of the JPA controllers
However, the application throws a NullPointerException when the JPA
controller attempts to get an entity manager with which to persist the
entity.
Below are the first few lines of the exception.
java.lang.NullPointerException
at
com.axle8.entity.jpaController.MarketerUserJpaController.getEntityManager(MarketerUserJpaController.java:
31)
at
com.axle8.entity.jpaController.MarketerUserJpaController.create(MarketerUserJpaController.java:
37)
at
com.axle8.web.server.SignUpServiceImpl.signUpMarketer(SignUpServiceImpl.java:
99)
I do NOT get the "No entity manager for persistence unit XYZ".
Below is the code where the exception occurs. Line 31 (where the
exception occurs) is the following line:
return emf.createEntityManager();
------------------------------------------------------------------------------------------------------------------------
public MarketerUserJpaController() {
emf = Persistence.createEntityManagerFactory("Axle8EntityPU");
}
private EntityManagerFactory emf = null;
public EntityManager getEntityManager() {
return emf.createEntityManager();
}
public void create(MarketerUser marketerUser) {
EntityManager em = null;
try {
em = getEntityManager();
em.getTransaction().begin();
em.persist(marketerUser);
//System.out.println(marketerUser.getUserId());
em.getTransaction().commit();
} finally {
if (em != null) {
em.close();
}
}
}
------------------------------------------------------------------------------------------------------------------------
The entity classes and JPA controllers have been tested successfully
on a J2EE server (Glassfish).
I'm thinking I need to deploy the whole thing to such a server.
Any assistance would be greatly appreciated! Please let me know
whether any further information would help
Regards,
Jin
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