JavaSpringJPA多列内部联接

Question

我对SpringJPA还是新手，我在尝试在一个实体上使用两列进行内部连接时遇到了一个问题

我有这些桌子

CREATE TABLE event (
id bigint unsigned auto_increment primary key comment 'id of the event',
user_id bigint unsigned not null comment 'id of the user',
organizer_id bigint unsigned not null comment 'id of the organizer user'
);

CREATE TABLE user (
id BIGINT UNSIGNED AUTO_INCREMENT PRIMARY KEY COMMENT 'user id',
email VARCHAR(256) NOT NULL COMMENT 'user email',
name VARCHAR(32) NOT NULL COMMENT  'user name',
surname VARCHAR(64) NOT NULL COMMENT 'user surname'
)

这件事发生在哪里。用户id和事件。组织者id映射到用户。身份证

我还让这些实体映射这些表

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    private String email;
    private String name;
    private String surname;

    @OneToMany(mappedBy = "user")
    private List<Event> events;
}

@Entity
public class Event {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id", nullable = false)
    private User user;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "organizer_id", nullable = false)
    private User organizer;
}

其思想是在用户列表中获取用户的所有事件，其中用户id由事件表上的用户id或组织者id映射

我曾尝试使用多个@joinColumn注释（并从@manyToOne（）中删除mappedBy），但遇到了以下错误：

组织。冬眠AnnotationException:外键引用的列数错误。应该是1

我找到的唯一解决方案是将它放在其他列表中以便使用，但我确信我缺少正确的方法，因为它应该是一个非常常见的用例

提前多谢

Answer 1

The idea is to get in the List of the user all the events of the user where the user id is mapped by user_id or organizer_id on events table.

JPA是数据库中实体的表示，在检索数据库中的内容后，您的需求需要进行后处理

I'm missing the correct way of doing it as it should be a very common use case.

在JPA级别，将两个不同的关系“合并”到一个集合中并不是很常见的用例

所以，一种方法是：

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;
    private String email;
    private String name;
    private String surname;

    @OneToMany(mappedBy = "user")
    private List<Event> userEvents;

    @OneToMany(mappedBy = "organizer")
    private List<Event> organizerEvents;
}