如何使用OneToOne双向关系正确管理关联的JPA实体? [英] How to properly manage associated JPA entities with OneToOne BiDirectional relation?

问题描述

假设有两个实体:主实体和从属实体.

Let's say 2 entities are given: master and dependant.

它们通常像dependants.master_id -> masters.id一样在数据库中定义，即从属实体拥有对主实体的引用.

They are defined in DB usually like dependants.master_id -> masters.id, i.e. the dependant entity holds the reference to the main entity.

在这种情况下，在JPA one2one双向关联中通常如下所示:

In JPA one2one BiDirectional association in this case usually looks like:

class Master {
    @OneToOne(mappedBy="master")
    Dependant dependant
}
class Dependant {
    @OneToOne
    @JoinColumn("master_id")
    Master master
}

这种方法导致必须处理关系的双方，例如:

And this approach causes the necessity to deal with both sides of relation like:

Master master = new Master();
Dependant dependant = new Dependant();
dependant.setMaster(master);
master.setDependant(dependant);
repository.save(master);

而不是像这样更直观，更接近业务逻辑:

instead of more intuitive and closer to business logic one like:

Master master = new Master();
Dependant dependant = new Dependant();
master.setDependant(dependant);
repository.save(master);

有没有通用的解决方法?我的意思是我不想从依赖方面支持协会.

Are there any common workarounds for this? I mean I don't want to mess with supporting the association from the dependant side.

推荐答案

一种解决方法可能是使用@PrePersist.对于这两个实体，您都可以实现以下方法:

One workaround might be using @PrePersist. For both entities you could implement methods like:

大师

@PrePersist
private void prePersist() {
    if(null == getDependant().getMaster()) {
        getDependant().setMaster(this);
    }
}

依赖

@PrePersist
private void prePersist() {
    if(null == getMaster().getDependant()) {
        getMaster().setDependant(this);
    }
}

或者也许只是省略空检查.

Or maybe just omitting the null checks.

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