Hibernate中的@ManyToOne映射不起作用

Question

我有两个类，具有多对一映射的Invite和Event ：一个事件有很多邀请。 以下是带有Hibernate批注的相关代码片段/ SQL：

db.Events

+-------------+--------------+------+-----+---------+----------------+
| Field       | Type         | Null | Key | Default | Extra          |
+-------------+--------------+------+-----+---------+----------------+
| event_id    | int(11)      | NO   | PRI | NULL    | auto_increment |
| name        | varchar(255) | YES  |     | NULL    |                |
+-------------+--------------+------+-----+---------+----------------+

db.Invites

+-----------+--------------+------+-----+---------+----------------+
| Field     | Type         | Null | Key | Default | Extra          |
+-----------+--------------+------+-----+---------+----------------+
| invite_id | int(11)      | NO   | PRI | NULL    | auto_increment |
| name      | varchar(255) | YES  |     | NULL    |                |
| event_fk  | int(11)      | NO   | MUL | NULL    |                |
+-----------+--------------+------+-----+---------+----------------+

DbInvite.java

@ManyToOne
private DbEvent event;

public DbInvite() {
}

public DbInvite(String name, DbEvent event) {
    this.name = name;
    this.event = event;
}

// getters and setters

DbEvent.java

@OneToMany(mappedBy = "event")
private Set<DbInvite> invites;

public DbEvent() {
}

public DbEvent(String name) {
    this.name = name;
}

// getters and setters

最后，我-这就是大多数Hibernate示例似乎停止的地方-我以以下方式创建实例：

DbEvent dbEvent = new DbEvent(name);
DbInvite dbInvite = new DbInvite(name, dbEvent);

我收到的错误是：

org.hibernate.engine.jdbc.spi.SqlExceptionHelper logExceptions
ERROR: Unknown column 'event_event_id' in 'field list'

我要去哪里错了？ 当主键明显是event_id时， event_event_id会从哪里来？

Answer 1

您需要为多对一指定连接列，否则JPA / Hibernate将采用默认值。

Answer 2

当您这样做时：

DbEvent dbEvent = new DbEvent(name);
//the id is setted in when persist into the db
dbEvent = someMethodThatPersistInDb(dbEvent);
//now the object have the id created in the db now insert the other one
DbInvite dbInvite = new DbInvite(name, dbEvent);
someMethodThatPersistInDb(dbInvite); 

我希望可以为您提供帮助，也许您可​​以发布其余的映射类以检查代码。