JPA批注，与单独包含的实例相对的列表 [英] JPA Annotations, lists opposed to separately included instances

问题描述

当我将JPA与数据集合一起使用，如何注释类型为List，ArrayList，Collections等(@OneToMany或@ManyToMany等)的成员时，对我来说很清楚.以下:

It is pretty clear to me when using JPA with a collection of data, how to annotate a member which is of type List, ArrayList, Collections, etc. (@OneToMany or @ManyToMany etc), but what if we have the following:

    @Entity    
    class page{

        Person creator;
        Person modifier;
        Person owner;
    }

在这种情况下，我要做出设计决定，使其不具有任何类型的人员实体集合，而要单独列出变量.我对如何正确注释这些成员感到困惑.

In this case, I want to make the design decision to not have any sort of collection of person entities, but rather separately listed variables. I am confusing myself as to how to correctly annotate these members.

我正确的假设是，即使它们被单独列出，我也应该将它们注释为列表，即

Am I correct in assuming that I should annotate them as if they were a list even though they are listed separately, ie

@ManyToMany，因为许多页面包含许多人"和许多人参与了许多页面"，而不是@ManyToOne许多页面包含一个人的创建者实例"(没有创建者实体仅是个人，创建者会仅是Page的成员变量)?

@ManyToMany because "Many Pages include many Persons" and "Many Persons are involved in Many Pages" as opposed to @ManyToOne "Many Pages include One Creator instance of Person" (There is no Creator entity only person, and creator would only be the member variable of Page) ?

推荐答案

您正在寻找的是ManyToOne关系.

What you are looking for is a ManyToOne relationship.

这很简单:

@ManyToOne

@ManyToOne

1. 一个人可以创建多少个页面?很多.
2. 有多少人可以创建一个页面?一个

@ManyToMany

@ManyToMany

1. 一个人可以修改多少个页面?许多
2. 有多少人可以修改一个页面?许多(但是我会在这里使用OneToMany并列出修改页面的人员列表.@ ManyToMany公平的做法很棘手)

@ManyToOne

@ManyToOne

1. 一个人如何拥有页面?很多
2. 人们如何拥有一个页面?一个(有时您可以拥有多个所有者， 但在您的情况下，我猜只需要一个所有者)

1. How pages can be owned by a single person?Many
2. How persons can own a single page? One (Well sometimes you can have more than one owner, but in your scenario, am guessing only one owner is desired)

所以:

@Entity
public class Page{

 @ManyToOne
 private Person creator;
 @OneToMany
 private List<Person> modifiers;
 @ManyToOne
 private Person owner; //which i guess may be the same as owner.

}

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