Hibernate关联映射-many to many 外键单向关联.

 

多对多的实例很多,这里说一个比较简单的例子,而且还是单向引用.. 比如说一个人可以对应多个地址,一个地址可以被多个人所拥有..

 

这就是对多多的关联关系,

 

 

在做多对多的关联的时候,一定要注意,别遗漏 中间表的配置。

 

下面是Pojo的类:

Person_FK_Many_to_Many:

public class Person_FK_Many_to_Many implements Serializable{
	
	private static final long serialVersionUID = -7132895885951796381L;
	private Integer id;
	private String name;
	private Integer age;
	
	private Set<Address_FK_Many_to_Many> addressFKManyToManieSet = new HashSet<Address_FK_Many_to_Many>();

                //getter 和setter方法省略;
}

 

 

Address_FK_Many_to_Many:

public class Address_FK_Many_to_Many {
	private Integer addressID;
	private String addressDetail;
	
                //getter和setter方法省略;
}

 

下面是Hibernate配置代码:

Person_FK_Many_to_Many.hbm.xml：

<?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>
 <class name="pack.java.model.Person_FK_Many_to_Many" table="ZHT_PERSON_FK_MANY_TO_MANY">
  <id name="id">
   		<generator class="identity"/>
  </id>
 	
 	<property name="name" column="NAME"></property>
 	<property name="age" column="AGE"></property>
 	<!--
                      ZHT_PERSON_ADDRESS_MANY_TO_MANY 这个set中的table,是指映射到数据库中的中间表; 用来存储personID 和 AddressID。
                  -->
 	<set name="addressFKManyToManieSet" lazy="false" table="ZHT_PERSON_ADDRESS_MANY_TO_MANY" inverse="false" cascade="all">
 		<key column="id" not-null="false" ></key>
 		<many-to-many column="addressID" class="pack.java.model.Address_FK_Many_to_Many">
 		</many-to-many>
 	</set>
 </class>
</hibernate-mapping>

 

Address_FK_Many_to_Many.hbm.xml

<?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>
	<class name="pack.java.model.Address_FK_Many_to_Many" table="ZHT_ADDRESS_FK_MANY_TO_MANY">
		<id name="addressID">
			<generator class="identity"></generator>
		</id>
		
		<property name="addressDetail" column="addressDetail"></property>
	</class>
</hibernate-mapping>

 

 

然后再Hibernate.cfg.xml中,把刚刚建立的两个*.hbm.xml文件。

<mapping resource="pack/java/model/Address_FK_Many_to_Many.hbm.xml"/>
 <mapping resource="pack/java/model/Person_FK_Many_to_Many.hbm.xml"/>

 

最后,就写一个测试类,来测试刚刚配置的单向多对多的关联关系.

 

package pack.java.test;

import java.util.List;
import java.util.Set;

import org.hibernate.Query;
import org.hibernate.Session;

import pack.java.hibernate.HibernateSessionFactory;
import pack.java.model.Address_FK_Many_to_Many;
import pack.java.model.Person_FK_Many_to_Many;
/**
 * 一个人可以对应多个地址，一个地址，也可以对应多个人。
 * @author Administrator
 *
 */
public class HibernateDemoManyToMany {
	private Session getSession(){
		Session session = HibernateSessionFactory.getSession();
		return session;
	}
	
	public static void main(String[] args) {
		HibernateDemoManyToMany demoManyToMany = new HibernateDemoManyToMany();
		Session session = demoManyToMany.getSession();
		//保存；
		demoManyToMany.savePerson(session);
		
		//查询;
		demoManyToMany.queryPerson(session);
	}
	
	private void queryPerson(Session session){
		//Person_FK_Many_to_Many personFKManyToMany = (Person_FK_Many_to_Many) session.load(Person_FK_Many_to_Many.class, 1);
		String hql = "select p from Person_FK_Many_to_Many p";
		Query query = session.createQuery(hql);
		List<Person_FK_Many_to_Many> list = query.list();
		
		for(Person_FK_Many_to_Many personFKManyToMany:list){
			System.out.println(personFKManyToMany.getId()+","+personFKManyToMany.getName()+","+personFKManyToMany.getAge());
			Set<Address_FK_Many_to_Many> addressFKManyToManies = personFKManyToMany.getAddressFKManyToManieSet();
			for (Address_FK_Many_to_Many addressFKManyToMany : addressFKManyToManies) {
				System.out.println(addressFKManyToMany.getAddressID()+","+addressFKManyToMany.getAddressDetail());
			}
		}
		
		session.close();
		
		System.out.println(list.get(0).getAddressFKManyToManieSet().size());
	}
	
	private void savePerson(Session session){
		Person_FK_Many_to_Many fkManyToMany1 = new Person_FK_Many_to_Many();
		fkManyToMany1.setAge(22);
		fkManyToMany1.setName("ZhouHaiTao");
		
		Person_FK_Many_to_Many fkManyToMany2 = new Person_FK_Many_to_Many();
		fkManyToMany2.setAge(23);
		fkManyToMany2.setName("ZhangSan");
		
		Address_FK_Many_to_Many addressFKManyToMany1 = new Address_FK_Many_to_Many();
		addressFKManyToMany1.setAddressDetail("北京市朝阳区");
		
		Address_FK_Many_to_Many addressFKManyToMany2 = new Address_FK_Many_to_Many();
		addressFKManyToMany2.setAddressDetail("深圳市罗湖区");
		
		Address_FK_Many_to_Many addressFKManyToMany3 = new Address_FK_Many_to_Many();
		addressFKManyToMany3.setAddressDetail("长沙市雨花区");
		
		fkManyToMany1.getAddressFKManyToManieSet().add(addressFKManyToMany1);
		fkManyToMany1.getAddressFKManyToManieSet().add(addressFKManyToMany2);
		
		fkManyToMany2.getAddressFKManyToManieSet().add(addressFKManyToMany2);
		fkManyToMany2.getAddressFKManyToManieSet().add(addressFKManyToMany3);
		
		session.beginTransaction().begin();
		//保存Peron第一个对象;
		session.save(fkManyToMany1);
		
		//保存Person第二个对象;
		session.save(fkManyToMany2);
		session.beginTransaction().commit();
	}
}

 

 

控制输出入如下:
1,ZhouHaiTao,22
1,深圳市罗湖区
2,北京市朝阳区

2,ZhangSan,23
1,深圳市罗湖区
3,长沙市雨花区