Hibernate映射文件之双向关联关系映射

一、双向1-N关联

Person类代码如下：

public class Person {
	private Integer id;
	private String name;
	private Set<Address> addresses = new HashSet<Address>();

        //省略getter和setter方法
}

 Address类代码如下：

public class Address implements Serializable {
	private Integer id;
	private String country;
	private String province;
	private String city;
	private Person person;

        //省略getter和setter方法
}

 

1、基于外键的双向1-N关联

Person.hbm.xml

<class name="Person" table="person" lazy="false">
        <id name="id" type="int" column="id">
        	<generator class="identity"/>
        </id>
        <property name="name" type="string" column="name" lazy="true"/>
        <set name="addresses" inverse="true" cascade="all">
        	<key column="person_id" unique="false"/>
        	<one-to-many class="Address"/>
        </set>
</class>

 Address.hbm.xml

<class name="Address" table="address">
        <id name="id" type="int" column="id">
        	<generator class="identity"/>
        </id>
        <property name="country" type="string" column="country"/>
        <property name="province" type="string" column="province"/>
        <property name="city" type="string" column="city"/>
        <many-to-one name="person" class="Person" column="person_id" unique="false"/>
</class>

 注意：

1、设置级联操作，在持久化Person对象时Hibernate将自动持久化Person关联的Address对象。

2、不让1的一端即Person端控制关联关系（即不让Hibernate在持久化Person和Address对象后调用update语句更新person_id字段）。

3、必须手动使Address对象知道它所关联的Person对象（即显示调用a1.setPerson(p1); ）。

 

2、基于连接表的双向1-N关联

Person.hbm.xml

<class name="Person" table="person" lazy="false">
        <id name="id" type="int" column="id">
        	<generator class="identity"/>
        </id>
        <property name="name" type="string" column="name" lazy="true"/>
        <set name="addresses" table="person_address" inverse="true" cascade="all">
        	<key column="person_id" unique="false" update="false"/>
        	<many-to-many class="Address" column="address_id" unique="true"/>
        </set>
</class>

 Address.hbm.xml

<class name="Address" table="address">
        <id name="id" type="int" column="id">
        	<generator class="identity"/>
        </id>
        <property name="country" type="string" column="country"/>
        <property name="province" type="string" column="province"/>
        <property name="city" type="string" column="city"/>
        <join table="person_address">
        	<key column="address_id" unique="true"/>
        	<many-to-one name="person" class="Person" column="person_id" unique="false"/>
        </join>
</class>