Hibernate 双向一对一关联

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本文只介绍实际开发中常用的设计模式（双向一对一关联）

其原理只是多对一的一种特例，只需增加一个unique="true"

下面看代码：

2个实体测试类：Man和Woman；理解为（一个男人可以娶一个女人，一个女人嫁一个男人）

package ray.one2one;public class Man {private int id;private String name;private Woman woman;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Woman getWoman() {return woman;}public void setWoman(Woman woman) {this.woman = woman;}}

Woman类：

package ray.one2one;public class Woman {private int id;private String name;private Man man;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public Man getMan() {return man;}public void setMan(Man man) {this.man = man;}}

要点：Man和Woman各自维护一个引用对象，互相指向一个对象

再看配置文件：

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="ray.one2one"><class name="Man" table="_man" lazy="true"><id name="id"><generator class="native"></generator></id><property name="name"></property><!-- 双向一对一关联, property-ref指明在关联类必须有Man类的man属性的get和set --><!-- 单向一对一则不需要此属性 --><one-to-one name="woman" class="Woman" property-ref="man"cascade="all"></one-to-one></class></hibernate-mapping>

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><hibernate-mapping package="ray.one2one"><class name="Woman" table="_woman" lazy="true"><id name="id"><generator class="native"></generator></id><property name="name"></property><!-- 双向一对一外键关联--><many-to-one name="man" unique="true" column="m_id" cascade="all"></many-to-one></class></hibernate-mapping>

最后看下测试类代码：

package ray.one2one;import org.hibernate.Session;import ray.SessionUtil.HibernateSessionFactory;public class Test {public static void main(String[] args) {Woman woman = new Woman();woman.setName("文苹");Man man = new Man();man.setName("雷盼");man.setWoman(woman);woman.setMan(man);Session session = HibernateSessionFactory.getSession();session.beginTransaction();session.save(woman);session.getTransaction().commit();session.close();}}

输出结果：

Hibernate:     alter table _woman         add index FK_gxnyefreb964vdnbshbbmreou (m_id),         add constraint FK_gxnyefreb964vdnbshbbmreou         foreign key (m_id)         references _man (id)

Hibernate:     insert     into        _man        (name)     values        (?)Hibernate:     insert     into        _woman        (name, m_id)     values        (?, ?)

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