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Date: Wed, 20 Feb 2013 00:08:13 +0100
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Subject: my fist openjpa porject / problem. help me please
From: Aitor Iturriondobeitia <laudio.info@gmail.com>
To: users@openjpa.apache.org
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hello
i an tring to build my firts openjpa app
i am readint this article (
http://java.dzone.com/articles/jpa-implementation-patterns) and building it
for this i make this:
1.- generic interface:
public interface IGenericDao<K, E> {
 void persist(E entity);
}
2.- other interface, my interface.
public interface IWsSrvTrackRequest  extends IGenericDao<Integer,
Wssrvtrackrequest>{
 void wsSrvRequestPersist(Wssrvtrackrequest request);
}
3.- generic JPA-DAO:
public abstract class JpaDao<K, E> implements IGenericDao<K, E> {
 protected Class<E> entityClass;

 @PersistenceContext
 protected EntityManager entityManager;

 public JpaDao() {
  ParameterizedType genericSuperclass = (ParameterizedType)
getClass().getGenericSuperclass();
  this.entityClass = (Class<E>)
genericSuperclass.getActualTypeArguments()[1];
 }
 public void persist(E entity) {
  entityManager.persist(entity);
 }
 }
}
4.- my jpa-dao implementation (the Wssrvtrackrequest obj is one jpa object
(entity)).
public class JpaWsSrvTrackRequestDaoImpl extends JpaDao<Integer,
Wssrvtrackrequest> implements IWsSrvTrackRequest {
 public void wsSrvRequestPersist(Wssrvtrackrequest request){
   entityManager.persist(request);
 }
}
i am make one main class:
public static void main(String[] args) {
  IWsSrvTrackRequest r = new JpaWsSrvTrackRequestDaoImpl();
  Wssrvtrackrequest v = new Wssrvtrackrequest();
  v.setWssrvreqIp("la ip");
  v.setWssrvreqOid("oid");
  v.setWssrvreqOiduser("oiduser");
  v.setWssrvreqRequest("la request");
  r.persist(v);
 }

 but it always returns one nullpointerexception.
 Exception in thread "main" java.lang.NullPointerException
 at com.caf.db.dao.JpaDao.persist(JpaDao.java:20)
 at com.caf.db.dao.ll.main(ll.java:20)

 Can you help me please?

 thanks

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