Hibernate关联关系映射（一对多/多对一）

于 2014-07-24 13:10:16 发布
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分类专栏： hibernate 文章标签： hibernate 关联关系
本文详细介绍了在数据库中如何通过一对一、一对多和多对一的关系来实现实体间的关联，包括基于主外键的关联、连接表的关联以及基于映射文件的关联方式，并通过示例代码演示了实现过程。

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一对多/多对一

双向的一对多/多对一关系是现实中最为常见的关联关系，即实体类A和B，一个A的实例关联多个B的实例，反过来，多个B的实例可能关联同一个A的实例，A到B的方向称为一对多，B到A的方向称为多对一。

public class A{
//A类其他属性
...
//Set集合，存储B的实例
Set bs = new HashSet();
}
public class B{
//B类其他属性
...
//A类的一个对象，表示B所关联的A的实例
A a;
}

基于主外键的一对多/多对一关联 

create table person(
	id int not null primary key,
	name varchar(20),
	age int
)
create table address(
	id int not null primary key,
	detail varchar(200),
	zipcode varchar(10),
	tel varchar(20),
	type varchar(20),
	person_id int,
	foreign key(person_id) references person(id)
)

Person类 

package onetomany;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

public class Person implements Serializable {

	private Integer id;
	private String name;
	private Integer age;
	private Set addresses = new HashSet(0);
	public Person() {
		super();
	}
	public Person(Integer id) {
		super();
		this.id = id;
	}
	
	public Person(Integer id, String name, Integer age) {
		super();
		this.id = id;
		this.name = name;
		this.age = age;
	}
	public Person(Integer id, String name, Integer age, Set addresses) {
		super();
		this.id = id;
		this.name = name;
		this.age = age;
		this.addresses = addresses;
	}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Integer getAge() {
		return age;
	}
	public void setAge(Integer age) {
		this.age = age;
	}
	public Set getAddresses() {
		return addresses;
	}
	public void setAddresses(Set addresses) {
		this.addresses = addresses;
	}
	
}


Person.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="onetomany.Person" table ="person" catalog="mldn">
	<id name="id" type ="java.lang.Integer">
		<column name="id"/>
		<generator class ="assigned"/>
	</id>
	<property name="name" type ="java.lang.String">
		<column name="name" length="20" />
	</property>
	<property name="age" type ="java.lang.Integer">
		<column name="age" />
	</property>
	<set name ="addresses" inverse="true">
		<key>
			<column name="person_id"/>
		</key>
		<one-to-many class="onetomany.Address"/>
	</set>
</class>
</hibernate-mapping>
Address.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="onetomany.Address" table ="address" catalog="mldn">
		<id name="id" type ="java.lang.Integer">
			<column name="id"/>
			<generator class="assigned"/>
		</id>
		<many-to-one name="person" class="onetomany.Person" fetch ="select" cascade="all">
			<column name="person_id"/>
		</many-to-one>
		<property name="detail" type="java.lang.String">
			<column name="detail" length="200"/>
		</property>
				<property name="zipcode" type="java.lang.String">
			<column name="zipcode" length="10"/>
		</property>
				<property name="tel" type="java.lang.String">
			<column name="tel" length="20"/>
		</property>
				<property name="type" type="java.lang.String">
			<column name="type" length="20"/>
		</property>
	</class>
</hibernate-mapping>


映射.hbm.xml文件 

	<mapping resource="onetomany/Person.hbm.xml" />
	<mapping resource="onetomany/Address.hbm.xml" />


测试类Testonetomany.java 

package test;

import org.hibernate.Session;
import org.hibernate.Transaction;

import onetomany.Address;
import onetomany.Person;
import util.HibernateSessionFactory;

public class Testonetomany {

	public static void main(String[] args) {
		Person person = new Person(1,"Tom",23);
		Address addr1 = new Address(10,"BeiJing","100009","010-110110","Office");
		Address addr2 = new Address(11,"DaLian","116400","0411-110110","Home");
		addr1.setPerson(person);
		addr2.setPerson(person);
		Session session = HibernateSessionFactory.getSession();
		Transaction tran = session.beginTransaction();
		session.save(addr1);
		session.save(addr2);
		tran.commit();
	}

}

package test;

import java.util.Set;

import org.hibernate.Session;
import org.hibernate.Transaction;

import onetomany.Address;
import onetomany.Person;
import util.HibernateSessionFactory;

public class Testonetomany {

	Session session = HibernateSessionFactory.getSession();
	Transaction tran = session.beginTransaction();
	public void run(){
		Person p = (Person)session.get(Person.class,1);
		Set<Address> addresses = p.getAddresses();
		for(Address addr:addresses){
			System.out.println(addr.getDetail()+" "+addr.getType());
		}
	}
	public static void main(String[] args) {
		/*Person person = new Person(1,"Tom",23);
		Address addr1 = new Address(10,"BeiJing","100009","010-110110","Office");
		Address addr2 = new Address(11,"DaLian","116400","0411-110110","Home");
		addr1.setPerson(person);
		addr2.setPerson(person);
		session.save(addr1);
		session.save(addr2);
		tran.commit();*/
		new Testonetomany().run();
	}

}

运行结果：




基于连接表的一对多/多对一关联

创建表：

create table person(
	id int not null primary key,
	name varchar(20),
	age int
)
create table address(
	id int not null primary key,
	detail varchar(200),
	zipcode varchar(10),
	tel varchar(20),
	type varchar(20),
)
create table personaddress(
       personid int not null,       
       addressid int not null primary key
)
Person.hbm.xml文件 

<?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="onetomany.Person" table ="person" catalog="mldn">
	<id name="id" type ="java.lang.Integer">
		<column name="id"/>
		<generator class ="assigned"/>
	</id>
	<property name="name" type ="java.lang.String">
		<column name="name" length="20" />
	</property>
	<property name="age" type ="java.lang.Integer">
		<column name="age" />
	</property>
	<set name ="addresses" table="personaddress">
		<key>
			<column name="personid"/>
		</key>
		<one-to-many class="onetomany.Address">
		<column name="addressid"/>
		</one-to-many>
	</set>
</class>
</hibernate-mapping>

Address.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="onetomany.Address" table ="address" catalog="mldn">
		<id name="id" type ="java.lang.Integer">
			<column name="id"/>
			<generator class="assigned"/>
		</id>
		<property name="detail" type="java.lang.String">
			<column name="detail" length="200"/>
		</property>
				<property name="zipcode" type="java.lang.String">
			<column name="zipcode" length="10"/>
		</property>
				<property name="tel" type="java.lang.String">
			<column name="tel" length="20"/>
		</property>
				<property name="type" type="java.lang.String">
			<column name="type" length="20"/>
		</property>
		<join table="personaddress">
			<key>
				<column name="addressid"></column>
			</key>
			<many-to-one name="person" cascade="all">
				<column name="personid"></column>
			</many-to-one>
		</join>
	</class>
</hibernate-mapping>

测试类 

public static void main(String[] args) {
		Person person = new Person(1,"Tom",23);
		Address addr1 = new Address(10,"BeiJing","100009","010-110110","Office");
		Address addr2 = new Address(11,"DaLian","116400","0411-110110","Home");
		addr1.setPerson(person);
		addr2.setPerson(person);
		Session session = HibernateSessionFactory.getSession();
		Transaction tran = session.beginTransaction();
		session.save(addr1);
		session.save(addr2);
		tran.commit();
	}

运行结果：




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