Question

我在Child表中定义了一个“Ordinal”INT列。出于某种原因，自动排序没有生效。我正在使用内存数据库的集成测试对此进行测试。也许这很重要？

public class ParentEntity
    ...
    @OneToMany
    @OrderColumn(name = "Ordinal")
    @JoinColumn(name = "ParentId", nullable = false)
    private List<ChildEntity> childEntities = new ArrayList<>();

public class ChildEntity
    ...
    @ManyToOne
    @JoinColumn(name = "ParentId", nullable=false, insertable=false, updatable=false)
    private ParentEntity parent;

谢谢！

Answer 1

问题是您的某个实体应该是owner of the bidirectional (ManyToOne) relationship:

public class ParentEntity
    ...
    @OneToMany(mappedBy="parent")//this mappedBy tells that ChildEntity is the owner of the entity
    @OrderColumn(name = "Ordinal")
    @JoinColumn(name = "ParentId", nullable = false)
    private List<ChildEntity> childEntities = new ArrayList<>();

public class ChildEntity
    ...
    @ManyToOne
    @JoinColumn(name = "ParentId", nullable=false, insertable=false, updatable=false)
    private ParentEntity parent;

摘自this page:

在JPA中，ManyToOne关系总是（几乎总是）需要定义OneToMany关系，ManyToOne总是如此定义外键（JoinColumn），OneToMany必须使用a mappedBy来定义它的逆ManyToOne。

查看此页

JPA @OrderColumn没有订购列表

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