Hibernate/JPA 注释中的多列连接 [英] Multi-Column Join in Hibernate/JPA Annotations

问题描述

我有两个实体，我想通过多个列加入它们.这些列由两个实体共享的 @Embeddable 对象共享.在下面的例子中，Foo 只能有一个 Bar 而 Bar 可以有多个 Foo(其中 Bar>AnEmbeddableObject 是 Bar 的唯一键.下面是一个例子:

I have two entities which I would like to join through multiple columns. These columns are shared by an @Embeddable object that is shared by both entities. In the example below, Foo can have only one Bar but Bar can have multiple Foos (where AnEmbeddableObject is a unique key for Bar). Here is an example:

@Entity
@Table(name = "foo")
public class Foo {
    @Id
    @Column(name = "id")
    @GeneratedValue(generator = "seqGen")
    @SequenceGenerator(name = "seqGen", sequenceName = "FOO_ID_SEQ", allocationSize = 1)
    private Long id;
    @Embedded
    private AnEmbeddableObject anEmbeddableObject;
    @ManyToOne(targetEntity = Bar.class, fetch = FetchType.LAZY)
    @JoinColumns( {
        @JoinColumn(name = "column_1", referencedColumnName = "column_1"),
        @JoinColumn(name = "column_2", referencedColumnName = "column_2"),
        @JoinColumn(name = "column_3", referencedColumnName = "column_3"),
        @JoinColumn(name = "column_4", referencedColumnName = "column_4")
    })
    private Bar bar;

    // ... rest of class
}

还有 Bar 类:

@Entity
@Table(name = "bar")
public class Bar {
    @Id
    @Column(name = "id")
    @GeneratedValue(generator = "seqGen")
    @SequenceGenerator(name = "seqGen", sequenceName = "BAR_ID_SEQ", allocationSize = 1)
    private Long id;
    @Embedded
    private AnEmbeddableObject anEmbeddableObject;

    // ... rest of class
}

最后是 AnEmbeddedObject 类:

@Embeddable
public class AnEmbeddedObject {
    @Column(name = "column_1")
    private Long column1;
    @Column(name = "column_2")
    private Long column2;
    @Column(name = "column_3")
    private Long column3;
    @Column(name = "column_4")
    private Long column4;

    // ... rest of class
}

显然模式规范化很差，这是一个限制，AnEmbeddedObject 的字段在每个表中重复.

Obviously the schema is poorly normalised, it is a restriction that AnEmbeddedObject's fields are repeated in each table.

我遇到的问题是当我尝试启动 Hibernate 时收到此错误:

The problem I have is that I receive this error when I try to start up Hibernate:

org.hibernate.AnnotationException: referencedColumnNames(column_1, column_2, column_3, column_4) of Foo.bar referencing Bar not mapped to a single property

我尝试将 JoinColumns 标记为不可插入和可更新，但没有运气.有没有办法用 Hibernate/JPA 注释来表达这一点?

I have tried marking the JoinColumns are not insertable and updatable, but with no luck. Is there a way to express this with Hibernate/JPA annotations?

推荐答案

这对我有用.在我的情况下，必须根据 3 个不同的列连接 2 个表 foo 和 boo.请注意，在我的情况下，boo 中的 3 个公共列不是主键

This worked for me . In my case 2 tables foo and boo have to be joined based on 3 different columns.Please note in my case ,in boo the 3 common columns are not primary key

即基于 3 个不同列的一对一映射

i.e., one to one mapping based on 3 different columns

@Entity
@Table(name = "foo")
public class foo implements Serializable
{
    @Column(name="foocol1")
    private String foocol1;
    //add getter setter
    @Column(name="foocol2")
    private String foocol2;
    //add getter setter
    @Column(name="foocol3")
    private String foocol3;
    //add getter setter
    private Boo boo;
    private int id;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "brsitem_id", updatable = false)
    public int getId()
    {
        return this.id;
    }
    public void setId(int id)
    {
        this.id = id;
    }
    @OneToOne
    @JoinColumns(
    {
        @JoinColumn(updatable=false,insertable=false, name="foocol1", referencedColumnName="boocol1"),
        @JoinColumn(updatable=false,insertable=false, name="foocol2", referencedColumnName="boocol2"),
        @JoinColumn(updatable=false,insertable=false, name="foocol3", referencedColumnName="boocol3")
    }
    )
    public Boo getBoo()
    {
        return boo;
    }
    public void setBoo(Boo boo)
    {
        this.boo = boo;
    }
}





@Entity
@Table(name = "boo")
public class Boo implements Serializable
{
    private int id;
    @Column(name="boocol1")
    private String boocol1;
    //add getter setter
    @Column(name="boocol2")
    private String boocol2;
    //add getter setter
    @Column(name="boocol3")
    private String boocol3;
    //add getter setter
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "item_id", updatable = false)
    public int getId()
    {
        return id;
    }
    public void setId(int id)
    {
        this.id = id;
    }
}

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