2011-08-25 158 views
4

我的课程看起来像这些。为什么同一列被选中4次?映射有什么问题?为什么Hibernate 4次选择相同的列?帮助映射?

@Entity @Table(name="CLIENTS") 
public class Client implements Serializable { 

    @Id @GeneratedValue @Column(name="GENERATED_ID") 
    private Long id; 

    @Column(name="NAME") 
    private String name; 

    @OneToMany(cascade=CascadeType.ALL, mappedBy="client", fetch=FetchType.EAGER) 
    private Map<ParamPK, Param> params = new HashMap<ParamPK, Param>(); 
} 

@Entity @Table(name="PARAMS") 
public class Param implements Serializable { 

    @EmbeddedId 
    private ParamPK paramPK; 

    @Column(name="VALUE") 
    private String value; 

    @ManyToOne @MapsId("clientId") 
    private Client client; 
} 

@Embeddable 
public class ParamPK implements Serializable { 

    @Column(name="PARAM_KEY") 
    private String key; 

    @Column(name="CLIENT_GENERATED_ID") 
    private Long clientId; 
} 

select生成的查询获得同一列4次。

/* from Client */ 
select 
    client0_.GENERATED_ID as GENERATED1_1_, 
    client0_.NAME as NAME1_ 
from 
    CLIENTS client0_ 

/* load one-to-many Client.params */ 
select 
    params0_.client_GENERATED_ID as client3_1_1_, 
    params0_.client_GENERATED_ID as client3_1_, 
    params0_.PARAM_KEY as PARAM1_1_, 
    params0_.CLIENT_GENERATED_ID as CLIENT3_1_, 
    params0_.client_GENERATED_ID as client3_0_0_, 
    params0_.PARAM_KEY as PARAM1_0_0_, 
    params0_.VALUE as VALUE0_0_ 
from 
    PARAMS params0_ 
where 
    params0_.client_GENERATED_ID=? 

注意使用Hibernate 3.5.3。其余的样板代码已被删除为无关紧要。

+0

你可以显示JPQL查询吗? – Jasper

+1

不确定它会有帮助,但是您是否尝试在您的地图上添加MapKey(name =“paramPK”)注释? –

+0

@Psy查询是普通的'em.createQuery(“来自客户端”);' – Ram

回答

3

你忘了告诉Hibernate是什么构成了参数图的关键。下面的注释添加到此地图:

@OneToMany(cascade=CascadeType.ALL, mappedBy="client", fetch=FetchType.EAGER) 
@MapKey(name = "paramPK") 
private Map<ParamPK, Param> params = new HashMap<ParamPK, Param>(); 

这告诉Hibernate的帕拉姆实体的paramPK属性是地图的关键。