java Hibernate进行正确的数据库查询，但返回空实体

Question

我在一个使用spring和hibernate的Vaadin java项目中工作。我的项目中有下一个实体：

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
import javax.persistence.CascadeType;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;

import org.hibernate.annotations.NamedQueries;
import org.hibernate.annotations.NamedQuery;

@Entity
@NamedQueries({
    @NamedQuery(name = "listarAreas", query = "SELECT a FROM AreaFuncional a"),
    @NamedQuery(name = "obtenerAreaPorId", query = "SELECT a FROM AreaFuncional a where a.id=?") })
public class AreaFuncional implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    private String nombre;

    @ManyToOne(cascade = { CascadeType.ALL })
    @JoinColumn(name = "area_pertenencia_id")
    private AreaFuncional areaPertenencia;

    @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    private Set<AreaFuncional> subAreas;

    @OneToMany(fetch = FetchType.LAZY)
    private Set<Empleado> empleados;
    private String telefonos;
    private String email;

    public AreaFuncional() {
        this.subAreas = new HashSet<AreaFuncional>();
        this.empleados = new HashSet<Empleado>();
    }
....

然后我有下一个问题：

public AreaFuncional obtenerAreaPorId(Long id) {
     AreaFuncional area = (AreaFuncional)
     getSessionFactory().getNamedQuery("obtenerAreaPorId").setLong(0, id)
     .uniqueResult();
    if (area == null)
        throw new RuntimeException("No existe el area con id " + id);
    return area;

}

当我执行查询时，我得到了正确的数据库mysql查询：

01:49:11,785 DEBUG http-bio-8080-exec-42 hibernate.SQL:109 - select areafuncio0_.id as id1_0_, areafuncio0_.area_pertenencia_id as area_per5_0_, areafuncio0_.email as email2_0_, areafuncio0_.nombre as nombre3_0_, areafuncio0_.telefonos as telefono4_0_ from AreaFuncional areafuncio0_ where areafuncio0_.id=?

如果我在控制台中执行mysql语句，我会得到正确的答案，但Hibernate会返回null对象

我找不到这个错误。 有人能帮我吗

Answer 1

如果要使用命名查询，则应将其用作：

 @NamedQuery(name = "obtenerAreaPorId", query = "SELECT a FROM AreaFuncional a where a.id= :id") })

及

 getSessionFactory().getNamedQuery("obtenerAreaPorId").setLong("id", id)

Answer 2

我认为你不能通过id参数； 测试一下这个：

@NamedQuery(name = "obtenerAreaPorId", query = "SELECT a FROM AreaFuncional a where a.id=:id") })

getSessionFactory().getNamedQuery("obtenerAreaPorId").setParameter("id",myId)