帮助在JPA 2.0中映射复合外键

Question

我是JPA的新手，我试图映射旧数据库。文件可以单独正确加载，但关系无法正常工作。任何帮助，将不胜感激。

的Java

@Entity 
@IdClass(ParentKey.class) 
public class Parent { 
    @Id 
    @Column(name="code") 
    private String code; 

    @Id 
    @Column(name="id") 
    private int id; 

    @OneToMany(mappedBy="parent") 
    private List<Child> children = new ArrayList<Child>(); 
} 

public class ParentKey { 
    private String code; 
    private int id; 
} 

@Entity 
@IdClass(ChildKey.class) 
public class Child { 
    @Id 
    @JoinColumns({ 
     @JoinColumn(name="code") 
     @JoinColumn(name="id") 
    }) 
    private Parent parent; 

    @Id 
    @Column(name="index") 
    private int index; 
} 

public class ChildKey { 
    private String code; 
    private int id; 
    private int index; 
} 

SQL

create table Parent(
    code char(4) not null, 
    id int not null, 
    primary key(code,id) 
); 

create table Child(
    code char(4) not null, 
    id int not null, 
    index int not null, 
    primary key(code, id, index), 
    foreign key(code, id) references Parent(code,id) 
); 

编辑1： 添加ChildKey和ParentKey类。

Answer 1

下面是复合标识1-N关系的DataNucleus文档的链接。可以帮助你识别出什么是错的。一开始你可能对儿童

http://www.datanucleus.org/products/accessplatform_3_0/jpa/orm/compound_identity.html#1_N_coll_bi

Answer 2

这里是OpenJPA中使用其ReverseMapping工具创建的，它似乎一切正常没有定义IdClass。

@Entity 
@Table(name="PARENT") 
@IdClass(ParentId.class) 
public class Parent { 
    @OneToMany(targetEntity=Child.class, mappedBy="parent", cascade=CascadeType.MERGE) 
    private Set childs = new HashSet(); 

    @Id 
    @Column(length=4) 
    private String code; 

    @Id 
    private int id; 

    //omitted getters, setters 
} 

public class ParentId implements Serializable { 
    public String code; 
    public int id; 

    //omitted getters, setters, toString, equals, hashcode 
} 

@Entity 
@Table(name="CHILD") 
@IdClass(ChildId.class) 
public class Child { 
    @Id 
    @Column(length=4) 
    private String code; 

    @Id 
    private int id; 

    @Id 
    private int index; 

    @ManyToOne(fetch=FetchType.LAZY, cascade=CascadeType.MERGE) 
    @JoinColumns({@JoinColumn(name="code"), @JoinColumn(name="id")}) 
    private Parent parent; 

    //omitted getters, setters 
} 

public class ChildId implements Serializable { 
    public String code; 
    public int id; 
    public int index; 

    //omitted getters, setters, toString, equals, hashcode 
} 

Answer 3

参见http://en.wikibooks.org/wiki/Java_Persistence/Identity_and_Sequencing#JPA_2.0 （添加@Id到@ManyToOne场）