Summary on 20080707: Hibernate operation on many-to-one relation

crazy_coder

于 2008-07-07 23:57:00 发布

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文章标签： hibernate insert class database exception setter

本文链接：https://blog.youkuaiyun.com/crazy_coder/article/details/2623168

本文详细介绍了Hibernate中多对一关系映射的具体实现方式，包括如何在Java类中定义对应关系，以及在配置文件中设置关键属性如not-null和cascade等。还特别注意了插入数据时的顺序问题。

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Hibernate many-to-one relation mapping:

public class Student{

    .....

    private CoreClass class;



    public CoreClass getter....

    public void setter

}





public class CoreClass{

....

}

<many-to-one name="class" column="classId" class="CoreClass" not-null="" cascade=""/>

Note

1. for the attribute not-null, if set to 'true', before insert data to database, hibernate will check, if class is null, throw exception before insert data

2. cascasde: mostly, the value should be 'save-update', should not be any value related to 'delete'

3. the order of insert one instance of class to database( class has already been assigned with vlaue) 3.1 insert class instance to db(if there is any mapping setting for CoreClass, it will done first) 3.2 insert student instance to db