@ManyToMany关系不保存

问题描述

我有一些 @ManyToMany 关系的实体：

@ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinTable(name = "buses_drivers",
        joinColumns = @JoinColumn (name = "driver_id_inner", referencedColumnName = "driver_id"),
        inverseJoinColumns = @JoinColumn (name = "bus_id_inner", referencedColumnName = "bus_id"))
private List<Bus> buses;

和

@ManyToMany(mappedBy = "buses", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private List<Driver> drivers;

当执行时将 Driver code>巴士型号，一切正常。表 buses_drivers 存储这些实体的所有键。但是，当使用驱动程序保存 Bus 模型时，表不会更改。我认为 inverseJoinColmns 映射存在问题。

When execute saving Driver model with some Bus models, all ok. Tables buses_drivers store all keys those entities. But when saving Bus model with drivers, table doesn't change. I think problem with inverseJoinColmns mapping.

推荐答案

这是预期的行为。在双向多对多关联中，一方必须是反面。在你的情况下，它是 Bus 端，因为它包含
$ b

That is the expected behaviour. In a bidirectional many-to-many association one side has to be the inverse side. In your case it is the Bus side because it contains mappedBy:

这意味着 Driver 是必需的，除非关系
是单向的。 >是关联的所有者，Hibernate在维护关联时只会检查那一方。

That means that Driver is the owner of the association and Hibernate will only check that side when maintaining the association.

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