JPA - 休眠：在另一个

Question

Conserider的一列几个表映射下表结构

country 
======= 
id 
code 
name_id 

label 
====== 
id 
code 
label_value_id 

translations 
============= 
id 
ref_id 
language 
value 

现在我需要找到一个JPA映射到地图country:name_id和label:label_value_id到翻译ref_id。我一直在用正确的英文术语来解释这种情况，但在体面的点击上空了。因此，数据库可以保存记录，如本例

country 
id: 1, code: BE, name_id: 30 

label 
id: 1, code: LABELA, label_value_id: 31 

translations 
id: 1, ref_id: 30, language: EN, value: BELGIUM 
id: 2, ref_id: 30, language: NL, value: BELGIE 
id: 3, ref_id: 31, language: EN, value: ALPHA_A 
id: 4, ref_id: 31, language: NL, value: ALFA_A 

在Java中我有3类

国家，标签和翻译，我会对国家@OneToMany关系和标签，这两个应该映射对翻译ref_id但我不知道如何编写我的@OneToMany代码来实现这一点。在正确的方向上的任何暗示将是非常理解的，溶液或手动

=====

更新2013-03-23

如上所述通过乔普，使用鉴别器是sollution BUT它没有开箱即用。我被迫使用hibernate注释@DiscriminatorOptions（force = true）。如果你不添加它，hibernate在获取所需的集合时完全忽略它的SQL查询中的Discriminator。

@Entity 
@Table(name = "testtranslations") 
@Inheritance(strategy = InheritanceType.SINGLE_TABLE) 
@DiscriminatorColumn(name = "DTYPE", discriminatorType = DiscriminatorType.STRING) 
@DiscriminatorOptions(force=true) 
public class TestTranslation extends DomainObject { 

    /** 
    * 
    */ 
    private static final long serialVersionUID = -6211853644196769521L; 

    private long id; 
    private String language; 
    private String value; 

    @Id 
    @GeneratedValue(strategy=GenerationType.AUTO, generator="testtranslations_seq_gen") 
    @SequenceGenerator(name="testtranslations_seq_gen", sequenceName="TESTTRANSLATIONS_SEQ") 
    @Column(name="testtranslation_id") 
    public long getId() { 
     return id; 
    } 

    @Column(name="language", length=3, nullable=false) 
    public String getLanguage() { 
     return language; 
    } 

    @Column(name="value") 
    public String getValue() { 
     return value; 
    } 

    @Override 
    public void setId(long id) { 
     this.id = id; 
    } 

    public void setLanguage(String language) { 
     this.language = language; 
    } 

    public void setValue(String value) { 
     this.value = value; 
    } 
} 


@Entity 
@Table(name = "testcountries") 
public class TestCountry extends DomainObject { 

    /** 
    * 
    */ 
    private static final long serialVersionUID = -9207081478447113501L; 

    private long id; 
    private String code; 
    private List<NameTranslation> name; 
    private List<DescriptionTranslation> description; 

    @Id 
    @GeneratedValue(strategy=GenerationType.AUTO, generator="testcountries_seq_gen") 
    @SequenceGenerator(name="testcountries_seq_gen", sequenceName="TESTCOUNTRIES_SEQ") 
    @Column(name="country_id") 
    public long getId() { 
     return id; 
    } 

    @Column(name="iso_code", length=3, nullable=false) 
    public String getCode() { 
     return code; 
    } 

    @OneToMany(mappedBy="refId") 
    public List<NameTranslation> getName() { 
     return name; 
    } 

    @OneToMany(mappedBy="refId") 
    public List<DescriptionTranslation> getDescription() { 
     return description; 
    } 

    @Override 
    public void setId(long id) { 
     this.id = id; 
    } 

    public void setCode(String code) { 
     this.code = code; 
    } 

    public void setName(List<NameTranslation> name) { 
     this.name = name; 
    } 

    public void setDescription(List<DescriptionTranslation> description) { 
     this.description = description; 
    } 
} 

@Entity 
@DiscriminatorValue("NAMETRANSLATION") 
public class NameTranslation extends TestTranslation { 

    /** 
    * 
    */ 
    private static final long serialVersionUID = 7197732491071768673L; 

    private TestCountry refId; 

    @ManyToOne(fetch=FetchType.LAZY) 
    @JoinColumn(name = "refId", nullable=false) 
    public TestCountry getRefId() { 
     return refId; 
    } 

    public void setRefId(TestCountry refId) { 
     this.refId = refId; 
    } 
} 

@Entity 
@DiscriminatorValue("DESCTRANSLATION") 
public class DescriptionTranslation extends TestTranslation { 

    /** 
    * 
    */ 
    private static final long serialVersionUID = -4128287237786410515L; 

    private TestCountry refId; 

    @ManyToOne(fetch=FetchType.LAZY) 
    @JoinColumn(name = "refId", nullable=false) 
    public TestCountry getRefId() { 
     return refId; 
    } 

    public void setRefId(TestCountry refId) { 
     this.refId = refId; 
    } 
} 

我做了必要的Hibernate映射并写了DbUnit的测试负载是通过ID TestCountry用以下数据

<TESTCOUNTRIES COUNTRY_ID="1" VERSION="0" ISO_CODE="BE" /> 
<TESTTRANSLATIONS TESTTRANSLATION_ID="1" VERSION="0" LANGUAGE="EN" VALUE="Belgium" REFID="1" DTYPE="NAMETRANSLATION" /> 
<TESTTRANSLATIONS TESTTRANSLATION_ID="2" VERSION="0" LANGUAGE="NL" VALUE="Belgie" REFID="1" DTYPE="NAMETRANSLATION" /> 
<TESTTRANSLATIONS TESTTRANSLATION_ID="3" VERSION="0" LANGUAGE="EN" VALUE="BelgiumDesc" REFID="1" DTYPE="DESCTRANSLATION" /> 
<TESTTRANSLATIONS TESTTRANSLATION_ID="4" VERSION="0" LANGUAGE="NL" VALUE="BelgieDesc" REFID="1" DTYPE="DESCTRANSLATION" /> 

我希望这将帮助其他人在未来，我只是难过没有JPA溶剂，我不得不被迫使用hibernate注释。

Answer 1

有点困难，因为你有两个表1或表的外键2.

确实有在JPA存在鉴别理念，为表继承。然后从共同的抽象表中派生出两个表格，并且具有不同的鉴别器字段。一个example。尽管这有点不同。

P.S.使用搜索关键字discriminatorValue和discriminatorColumn查找更好的示例。