如何手动为@GeneratedValue设置值 [英] How to manually set a value for @GeneratedValue

问题描述

使用Spring Data JPA进行Spring引导. Postgres数据库.

Have a Spring boot with Spring Data JPA. Postgres DB.

一般实体:

@Entity
@Table
class Entity {

@Id
@GeneratedValue
private int id;

}

当我尝试使用指定的id值进行输入时，结果我看到它被@GeneratedValue忽略并生成.

when I try to make an entry with a specified id value, as a result I see that it is ignored and generated by @GeneratedValue.

如何克服这个问题?

推荐答案

发布解决方案，在对整个持久性过程进行调试后我来到了解决方案(并未说明这是正确的方法，但我确实没有这样做)找到也许我配置有误"的任何地方):

Posting the solution, to which I came after doing a debug of the whole persist process (not stating that this is the right way, but I literally didn't find any spot of "maybe I configured something wrong"):

public class MyGenerator extends SequenceStyleGenerator {

    @Override
    public Serializable generate(SharedSessionContractImplementor session, Object object) throws HibernateException {
        return Optional.of(object)
                .filter(Entity.class::isInstance)
                .map(Entity.class::cast)
                .map(Entity::getId)
                .filter(i -> i > 0)
                .map(Serializable.class::cast)
                .orElse(super.generate(session, object));
    }
)

和实体:

@Entity
class Entity implements Serializable {

@GenericGenerator(name = "myGenerator", strategy = "org.a.b.c.generators.MyGenerator")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "myGenerator")
    private Integer id;

}

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