对于多对多的关联关系处理，前面我讲解了在数据库中建立第三张表用于维护两者的关联关系，现在我来讲解另一种比较常用且通用的处理方式，那就是将这个多对多的关联关系拆解成两个一对多的关联关系，意取从这个多对多的关联关系中提取出一个中间实体，用来表示两者的多对多关联关系，这个中间实体在数据库中存在相应的数据表映射。

　　一。Husband

package com.orm.model; import java.util.List; /** * Created by IntelliJ IDEA. * User: Zhong Gang * Date: 10/18/11 * Time: 3:23 PM */ public class Husband extends DomainObject { private String name; private List<Couple> couples; public Husband(String name) { this.name = name; } }

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping default-access="field"> <class name="com.orm.model.Husband" table="husband"> <id name="id" column="id" type="java.lang.Integer"> <generator class="native"/> </id> <property name="name" column="name" type="java.lang.String"/> <bag name="couples" cascade="all"> <key column="husbandid"/> <one-to-many class="com.orm.model.Couple"/> </bag> </class> </hibernate-mapping>

　　二。Wife

package com.orm.model; import java.util.List; /** * Created by IntelliJ IDEA. * User: Zhong Gang * Date: 10/18/11 * Time: 3:23 PM */ public class Wife extends DomainObject{ private String name; private List<Couple> couples; public Wife(String name) { this.name = name; } }

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping default-access="field"> <class name="com.orm.model.Wife" table="wife"> <id name="id" column="id" type="java.lang.Integer"> <generator class="native"/> </id> <property name="name" column="name" type="java.lang.String"/> <bag name="couples" cascade="all"> <key column="wifeid"/> <one-to-many class="com.orm.model.Couple"/> </bag> </class> </hibernate-mapping>

　　三。Couple

package com.orm.model; import java.util.List; /** * Created by IntelliJ IDEA. * User: Zhong Gang * Date: 10/18/11 * Time: 3:23 PM */ public class Couple extends DomainObject{ private Husband husband; private Wife wife; public Couple(Husband husband, Wife wife) { this.husband = husband; this.wife = wife; } }

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping default-access="field"> <class name="com.orm.model.Couple" table="couple"> <id name="id" column="id" type="java.lang.Integer"> <generator class="native"/> </id> <many-to-one name="husband" class="com.orm.model.Husband" column="husbandid"/> <many-to-one name="wife" class="com.orm.model.Wife" column="wifeid"/> </class> </hibernate-mapping>

　　四。测试代码

package com.orm; import com.orm.model.Couple; import com.orm.model.Husband; import com.orm.model.Wife; import com.orm.service.CoupleService; import junit.framework.TestCase; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; import java.util.ArrayList; import java.util.List; /** * Created by IntelliJ IDEA. * User: Zhong Gang * Date: 10/18/11 * Time: 3:40 PM */ public class HibernateManyToManyTest extends TestCase { private CoupleService coupleService; @Override public void setUp() throws Exception { ApplicationContext context = new ClassPathXmlApplicationContext("classpath:testDataSource.xml"); coupleService = (CoupleService) context.getBean("coupleService"); } public void testManyToMany() throws Exception { Wife wife1 = new Wife("wife1"); Wife wife2 = new Wife("wife2"); coupleService.saveOrUpdate(wife1); coupleService.saveOrUpdate(wife2); Husband husband1 = new Husband("husband1"); Husband husband2 = new Husband("husband2"); coupleService.saveOrUpdate(husband1); coupleService.saveOrUpdate(husband2); Couple couple1 = new Couple(husband1, wife1); Couple couple2 = new Couple(husband1, wife2); Couple couple3 = new Couple(husband2, wife1); Couple couple4 = new Couple(husband2, wife2); coupleService.saveOrUpdate(couple1); coupleService.saveOrUpdate(couple2); coupleService.saveOrUpdate(couple3); coupleService.saveOrUpdate(couple4); } }

　　测试结果截图

　　最后附上源码以供参考