内容简介:hibernate双向一对一主键关联映射XML与注解版
双向一对一关联映射原理:
双向的主键关联其实是单向一对一主键关联的一种特殊情况,只不过要在关联对象的两端的映射文件中都要进行<one-to-one>的配置,另外还要在主映射的主键一端采用foreign外键关联属性。
这里同样使用Person和IdCard来讨论,一个人对应着一个唯一的身份证,而且一个身份证也唯一映射着一个人,所以这就产生了双向的关联关系,Person的主键同样也是IdCard的主键,分别是主键的同时也是外键,这种关联关系成为双向一对一映射,表现到关系模型中可如下图:
(1)XML版
SQL文件:
CREATE TABLE `person` ( `id` varchar(255) NOT NULL, `pname` varchar(255) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE `idcard` ( `id` varchar(255) NOT NULL, `cardnum` varchar(255) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Person类:
package Hibernate_demo1.Demo11.Entity; public class Person { private String id; private String pname; private IdCard idcards; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getPname() { return pname; } public void setPname(String pname) { this.pname = pname; } public IdCard getIdcards() { return idcards; } public void setIdcards(IdCard idcards) { this.idcards = idcards; } }
IdCard类:
package Hibernate_demo1.Demo11.Entity; public class IdCard { private String id; private String cardNum; private Person persons; public Person getPersons() { return persons; } public void setPersons(Person persons) { this.persons = persons; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getCardNum() { return cardNum; } public void setCardNum(String cardNum) { this.cardNum = cardNum; } }
IdCard.hbm.xml映射文件
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="Hibernate_demo1.Demo11.Entity.IdCard" table="IdCard"> <id name="id" type="java.lang.String"> <column name="id"/> <generator class="uuid"> </generator> </id> <property name="cardNum" column="cardNum"/> <!-- 在映射文件中添加外键属性persons,并添加对应的<one-to-one>标签 目的是强制约束person类来实现一对一的映射关系,最后在映射中将constrained属性设为true 保证强制约束关系。 --> <one-to-one name="persons" constrained="true"></one-to-one> </class> </hibernate-mapping>
双向一对一唯一外键映射关键映射代码——在IdCard端新加入如下标签映射:
<one-to-one name="person"property-ref="idCard"/>
注意:一对一唯一外键关联双向采用<one-to-one>标签映射,必须指定<one-to-one>标签中的property-ref属性为关系字段的名称。
Person.hbm.xml映射文件
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping> <class name="Hibernate_demo1.Demo11.Entity.Person" table="person"> <id name="id"> <generator class="uuid"> </generator> </id> <property name="pname" column="pname"/> <!-- one-to-one标签指示Hibernate如何加载其关联对象,默认根据主键加载,也就是拿到关系字段值,根据对端的主键来加载关联对象 --> <one-to-one name="idcards"></one-to-one> </class> </hibernate-mapping>
测试类:
package Hibernate_demo1.Demo11; import org.hibernate.Session; import Hibernate_demo1.Demo11.Entity.IdCard; import Hibernate_demo1.Demo11.Entity.Person; import Hibernate_demo1.Demo11.Util.HibernateUtils; public class App { public static void main( String[] args ) { Session session = null; try{ session = HibernateUtils.getSession(); session.beginTransaction(); //创建person对象,并保存 Person person=new Person(); person.setPname("fendo"); session.save(person); //创建idCard对象,并保存 IdCard idcard=new IdCard(); idcard.setCardNum("123456789"); idcard.setPersons(person); session.save(idcard); session.getTransaction().commit(); }catch(Exception e){ e.printStackTrace(); session.getTransaction().rollback(); }finally{ HibernateUtils.closeSession(session); } } }
执行结果如下:
Hibernate: insert into person (pname, id) values (?, ?) Hibernate: insert into IdCard (cardNum, id) values (?, ?)
运行结果如下:
Person表
idcard表
示例: http://download.csdn.net/detail/u011781521/9834854
(2)注解版
Person类:
package Hibernate_demo1.Demo12.Entity; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToOne; import javax.persistence.PrimaryKeyJoinColumn; import javax.persistence.Table; import org.hibernate.annotations.GenericGenerator; @Entity @Table(name="person") public class Person { @Id @GenericGenerator(name="uuidGenerator", strategy="uuid") @GeneratedValue(generator="uuidGenerator") private String id; @Column(name="pname") private String pname; @OneToOne(cascade=CascadeType.ALL) @PrimaryKeyJoinColumn private IdCard idcards; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getPname() { return pname; } public void setPname(String pname) { this.pname = pname; } public IdCard getIdcards() { return idcards; } public void setIdcards(IdCard idcards) { this.idcards = idcards; } }
IdCard类:
package Hibernate_demo1.Demo12.Entity; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToOne; import javax.persistence.PrimaryKeyJoinColumn; import javax.persistence.Table; import org.hibernate.annotations.GenericGenerator; @Entity @Table(name="idcard") public class IdCard { @Id @GenericGenerator(name="uuidGenerator", strategy="uuid") @GeneratedValue(generator="uuidGenerator") private String id; @Column(name="cardNum") private String cardNum; @OneToOne @PrimaryKeyJoinColumn private Person persons; public Person getPersons() { return persons; } public void setPersons(Person persons) { this.persons = persons; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getCardNum() { return cardNum; } public void setCardNum(String cardNum) { this.cardNum = cardNum; } }
测试类:
package Hibernate_demo1.Demo12; import java.util.HashSet; import java.util.Set; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import Hibernate_demo1.Demo12.Entity.IdCard; import Hibernate_demo1.Demo12.Entity.Person; public class App { public static void main( String[] args ) { SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory(); Session session = sessionFactory.getCurrentSession(); Transaction tx = session.beginTransaction(); //创建person对象,并保存 Person person=new Person(); person.setPname("fendo"); session.save(person); //创建idCard对象,并保存 IdCard idcard=new IdCard(); idcard.setCardNum("123456789"); idcard.setPersons(person); session.save(idcard); tx.commit(); session.close(); } }
执行结果如下:
Hibernate: insert into person (pname, id) values (?, ?) Hibernate: insert into idcard (cardNum, id) values (?, ?)
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