Hibernate 关联存储机制

Hibernate Many to one:
how was the object stored?
======================================================================
[b]Userb]

<hibernate-mapping 
	package="com.smith.hibernate.bean">

	<class name="User" table="glass_user" lazy="true">
		
		<id name="id" type="int" column="id">
			<generator class="native"/>
		</id>
		<property name="name" 
		          column="name"
		          type="java.lang.String"
		          length="50"
		          />
		
		<property name="password" 
		        type="java.lang.String"
				not-null="true"
				length="20"
				column="password"/>
				
		<property name="des"
		          type="java.lang.String"
		          length="100"
		          column="des"/>
		 <property name="newDate"/>
		 
		<many-to-one name="group"
		             column="groupId"
		             class="Group"
		             cascade="save-update"
		             lazy="false"
		             >
		</many-to-one>
		
	</class>

======================================================================Group
<hibernate-mapping package="com.smith.hibernate.bean">

<class name="Group" table="glass_group" lazy="true">

<id name="id" column="id">
<generator class="assigned" />
</id>
<property name="des" type="java.lang.String" length="100"
column="des" />

<property name="name" column="name" type="java.lang.String"
length="50" />

</class>

</hibernate-mapping>
======================================================================SQL

Hibernate: 
    select
        group_.id,
        group_.des as des1_,
        group_.name as name1_ 
    from
        glass_group group_ 
    where
        group_.id=?
Hibernate: 
    insert 
    into
        glass_user
        (id, name, password, des, newDate, groupId) 
    values
        (null, ?, ?, ?, ?, ?)
Hibernate: 
    insert 
    into
        glass_group
        (des, name, id) 
    values

======================================================================
由此可见Hibernat emany to one存储方式 ：

• 1.先存主对象User
• 2.再存关联对象Group
• 3.更新主对象的groupId （关联的外键值）