hibernate映射数据库时@ManyToOne和@OneToMany

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hibernate映射数据库时@ManyToOne和@OneToMany_MySQL

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Jun 01, 2016 pm 01:28 PM

hibernatedatabase

Hibernate

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第一次用hibernate自动生成表，涉及到多个表的外键，用到了@OneToMany和@ManyToOne注解碰到了几个错误。

首先声明一个基础，@OneToMany和@ManyToOne两个注解没有必要一一对应

第一个问题：@OneToMany和@ManyToOne的区别

使用@ManyToOne时是在本类对应的数据库表中生成字段，比如项目经理类和程序员类，一个项目经理下管理多个程序员，

也就是在这个Programmer对应的表t_programmer中生成字段“mid”；

而@OneToMany注解则是在多的一方对应的表生成字段；

那么会在t_programmer表中生成字段“mid”；多个programmer对应一个项目经理。

值得一提的是当使用@OneToMany时需要使用Setj集合，否则报错

这些都是基础的东西，总结一下以后忘了随时看看

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