Hibernate关联映射之

Hibernate关联映射之_一对一

数据库模型

　　一般对一对一的关系而言，会存在一个主从关系。如人与身份证，就是一个一对一关系，人是主，身份证是从

Person

　　PK：id

　　　　name

　　　　age

Id_Card

　　PK、FK：id

　　　　useful_life

一般在设计的时候，对于主表的id，由自增长或序列产生，从表的主键id可以直接使用主表的主键id，不需要自己重新生成

Domain

 1 package org.zln.hibernate.domain;
 2 
 3 /**
 4  * Created by coolkid on 2015/6/20 0020.
 5  */
 6 public class Person {
 7     private int id;
 8     private String name;
 9     private IdCard idCard;
...43 }

 1 package org.zln.hibernate.domain;
 2 
 3 
 4 /**
 5  * Created by coolkid on 2015/6/20 0020.
 6  */
 7 public class IdCard {
 8     private int id;
 9     private String usefulLife;//证件有效期
10     private Person person;
...
43 }

XML

Person.hbm.xml

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC
 3     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 4     "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 5 <hibernate-mapping package="org.zln.hibernate.domain">
 6 
 7     <class name="Person" table="person">
 8         <id name="id" column="id">
 9             <generator class="native"/>
10         </id>
11         <property name="name" column="name"/>
12         <!--一对一关系映射-->
13         <one-to-one name="idCard" />
14     </class>
15 
16 </hibernate-mapping>

IdCard.hbm.xml

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC
 3     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 4     "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 5 <hibernate-mapping package="org.zln.hibernate.domain">
 6 
 7     <class name="IdCard" table="id_card">
 8         <id name="id" column="id">
 9             <!--主键依赖类中的属性-->
10             <generator class="foreign">
11                 <!--外键从person属性中引用过来  从person 的 getId 方法获取-->
12                 <param name="property">person</param>
13             </generator>
14         </id>
15         <property name="usefulList" column="useful_life"/>
16         <!--一对一关系映射-->
17         <one-to-one name="person" />
18     </class>
19 
20 </hibernate-mapping>

Dao

 1 package org.zln.hibernate.dao;
 2 
 3 import org.hibernate.Session;
 4 import org.hibernate.Transaction;
 5 import org.zln.hibernate.domain.IdCard;
 6 import org.zln.hibernate.domain.Person;
 7 import org.zln.hibernate.utils.HibernateUtils;
 8 
 9 /**
10  * Created by coolkid on 2015/6/20 0020.
11  */
12 public class PersonDao {
13 
14     /**
15      * 保存Person及其IdCard
16      * @param person 人
17      * @param idCard 身份证
18      */
19     public void savePerson(Person person,IdCard idCard){
20         Session session = null;
21         Transaction transaction = null;
22         try {
23             session = HibernateUtils.getSession();
24             transaction = session.beginTransaction();
25 
26             person.setIdCard(idCard);
27             idCard.setPerson(person);
28 
29             session.save(person);
30             session.save(idCard);
31 
32             transaction.commit();
33         }finally {
34             if (session != null){
35                 session.close();
36             }
37         }
38     }
39 
40     /**
41      * 通过id查询person
42      * @param person person
43      * @return Person
44      */
45     public Person getPerson(Person person){
46         Session session = null;
47         Person person1 = null;
48         try {
49             session = HibernateUtils.getSession();
50             person1 = (Person) session.get(Person.class,person.getId());
51         }finally {
52             if (session != null){
53                 session.close();
54             }
55         }
56         return person1;
57     }
58 }

另一种一对一关系的实现，就是使用多对一的方法，但是对“多”加唯一性约束

在配置IdCard的name属性时，使用<many-to-one>标签，对应的column是person_id，设置unique="true"，这样也实现了一对一关系映射

 1 <?xml version="1.0"?>
 2 <!DOCTYPE hibernate-mapping PUBLIC
 3     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 4     "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 5 <hibernate-mapping package="org.zln.hibernate.domain">
 6 
 7     <class name="IdCard" table="id_card">
 8         <id name="id" column="id">
 9             <generator class="native"/>
10         </id>
11         <property name="usefulList" column="useful_life"/>
12         <many-to-one name="person" column="person_id" unique="true" not-null="true"/>
13     </class>
14 
15 </hibernate-mapping>