JPA更新多对多删除记录 [英] JPA update many-to-many deleting records

问题描述

我在两个实体之间有@ManyToMany关系。当我在拥有方执行更新时，JPA似乎从我的数据库中删除所有链接的记录并重新插入它们。对我来说这是一个问题，因为我有一个MySQL触发器，在删除记录之前触发。如何解决这个问题？

I have a @ManyToMany relationship between two entities. When I perform an update on the owning side, it appears that JPA deletes all the linked records from my database and re-inserts them. For me this is a problem because I have a MySQL trigger that fires before a record is deleted. Any ideas on how to get around this problem?

@Entity
public class User {

    @Id
    @Column(name="username")
    private String username;

    ...

    @ManyToMany
    @JoinTable(name="groups", joinColumns=
        @JoinColumn(name="username", referencedColumnName="username"),
            inverseJoinColumns=@JoinColumn(name="groupname",
                    referencedColumnName="type_id"))
    private List<UserType> types;

    ...

}

@Entity
public class UserType {

    @Id
    @Column(name="type_id")
    private String id;

    @ManyToMany(mappedBy="types")
    private List<User> users;

    ...
} 

推荐答案

看来我的问题是我没有合并实体。

It appears my problem was that I was not merging the entity.

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