nullpointerexception - 注入的托管属性为空

Question

我有一个 JSF 托管 bean 来创建依赖于应用程序的用户实例（UserFactory 接口实现者）。我想在 EJB 容器中使用这个工厂。应用程序引发 NullPointerException，因为 UserWithRolesDAL.userFactory 的值为 null。但为什么？

@Stateless
@LocalBean
public class UserWithRolesSER
{
  @Inject
  private UserWithRolesBUS userBUS;

  ... 
}

@Dependent
class UserWithRolesBUS
{
  @Inject
  private UserWithRolesDAL userDAL;

  ... 
}

@Dependent
class UserWithRolesDAL
{
  @ManagedProperty( value = "#{userFactory}" )
  private UserFactory userFactory;

  ... 
}

public interface UserFactory
{
  public UserWithRoles createUser();
}

@ManagedBean
@ApplicationScoped
@Named( value = "userFactory" )
public class XUserFactory implements UserFactory
{
  ...
}