Question

我在使用JPA和Facade modell时遇到问题，因为我现在不知道如何使用它。我有一个名为“Kandidatenstamm”的课程（这是一种恩赐）。对于这个Kandidatenstamm，存在Facade和Controller。还有一个抽象门面和一个抽象控制器。那么我在bean中需要做什么，例如从id = 4的数据库中获取对象？

这是我的代码

抽象立面

public abstract class AbstractFacade<T> {
private Class<T> entityClass;

public AbstractFacade(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();
}

}

KandidatenstammFacade

 @Stateless
public class KandidatenstammFacade extends AbstractFacade<Kandidatenstamm> {
@PersistenceContext(unitName = "ffswebadministrationPU")
private EntityManager em;

@Override
protected EntityManager getEntityManager() {
    return em;
}

public KandidatenstammFacade() {
    super(Kandidatenstamm.class);
}

}

Answer 1

好的，我自己设法了。只进行EJB注入并使用Facade。这里以“Personenstamm”为例（原则上与“Kandidatenstamm”相同）

@EJB
private PersonenstammFacade personenstammFacade;

....

List <Personenstamm> personlist;
personlist = personenstammFacade.findAll();

....
//do what you want with this list

如何使用JPA和Facade？

1 个答案: