I want to create a remote EJB for an entity class. Is there a way of implementing a method with one parameter beign an object of a class that specifically has the @Entity annotation? The purpose of this, is to create just one bean for all my entities.
Example:
public void save(Entity ent){
em.persist(ent);
}
If you just have 1 ejb for all entities you will soon run into problems when you have to handle some of them in a special way.
But you can do like this with an abstract super-ejb, and still have 1 ejb per entity, but its very easy to create. And you can still overwrite the default, inherited methods.
public abstract class AbstractEjb<T> {
private Class<T> entityClass;
public AbstractEjb(Class<T> entityClass) {
this.entityClass = entityClass;
}
protected abstract EntityManager getEntityManager();
public void create(T entity) {
getEntityManager().persist(entity);
}
public void edit(T entity) {
getEntityManager().merge(entity);
}
public void remove(T entity) {
getEntityManager().remove(getEntityManager().merge(entity));
}
public T find(Object id) {
return getEntityManager().find(entityClass, id);
}
public List<T> findAll() {
javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
cq.select(cq.from(entityClass));
return getEntityManager().createQuery(cq).getResultList();
}
public List<T> findRange(int[] range) {
javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
cq.select(cq.from(entityClass));
javax.persistence.Query q = getEntityManager().createQuery(cq);
q.setMaxResults(range[1] - range[0] + 1);
q.setFirstResult(range[0]);
return q.getResultList();
}
public int count() {
javax.persistence.criteria.CriteriaQuery cq = getEntityManager().getCriteriaBuilder().createQuery();
javax.persistence.criteria.Root<T> rt = cq.from(entityClass);
cq.select(getEntityManager().getCriteriaBuilder().count(rt));
javax.persistence.Query q = getEntityManager().createQuery(cq);
return ((Long) q.getSingleResult()).intValue();
}
}
To implement for an entity just do
@Stateless
public class TestEjb extends AbstractEjb<TestEntity> {
@PersistenceContext(unitName = "...")
private EntityManager em;
public TestEjb() {
super(TestEntity.class);
}
public EntityManager getEntityManager() {
return em;
}
}
Source: Generate JSF pages from entity classes in Netbeans.
