Question

我想用bean注入我的servlet。但每次我尝试我都会收到此错误

javax.servlet.ServletException: Error instantiating servlet class servlet.RegisterServlet

我猜测某些注释缺失或错误。那我该怎么做呢？有没有其他方法可以注入到servlet中？

RegisterServlet

public class RegisterServlet extends HttpServlet {
    @EJB
    protected KorisniciFacade kf;

    public RegisterServlet() {
       // stuff
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //more stuff
    }

    private boolean invalidUser(String username) {
         // stuff
    }

}

FacadeLocal

    @Local
public interface KorisniciFacadeLocal {

    void create(Korisnici korisnici);

    void edit(Korisnici korisnici);

    void remove(Korisnici korisnici);

    Korisnici find(Object id);

    List<Korisnici> findAll();

    List<Korisnici> findRange(int[] range);

    int count();

}

门面

    @Stateless
public class KorisniciFacade extends AbstractFacade<Korisnici> implements KorisniciFacadeLocal {
    @PersistenceContext(unitName = "MobMelPU")
    private EntityManager em;

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

    public KorisniciFacade() {
        super(Korisnici.class);
    }

}

AbstractFacade

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();
    }

}

Answer 1

你的类型错了。你应该在这里使用界面：

@EJB
protected KorisniciFacade kf;

正确：

@EJB
protected KorisniciFacadeLocal kf;

将Bean注入Servlet

1 个答案: