传智播客Hibernate视频教程学习笔记18

最新推荐文章于 2009-08-08 20:58:00 发布

原创最新推荐文章于 2009-08-08 20:58:00 发布 · 595 阅读

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#hibernate #generator #class #string #encoding #date

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本文通过具体的Java类和Hibernate配置文件示例，深入探讨了一对一关系映射的实现方式及注意事项，特别是如何正确设置关联关系以确保数据的一致性和完整性。

一对一关系映射

Person.java

package domain; public class Person { private int id; private String name; private IdCard idCard; 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 IdCard getIdCard() { return idCard; } public void setIdCard(IdCard idCard) { this.idCard = idCard; } }

IdCard.java

package domain; import java.util.Date; public class IdCard { private int id; private Date usefulLife; private Person person; public int getId() { return id; } public void setId(int id) { this.id = id; } public Date getUsefulLife() { return usefulLife; } public void setUsefulLife(Date usefulLife) { this.usefulLife = usefulLife; } public Person getPerson() { return person; } public void setPerson(Person person) { this.person = person; } }

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 package="domain"> <class name="Person"> <id name="id"> <generator class="native"/> </id> <property name="name"></property> <one-to-one name="idCard"></one-to-one> </class> </hibernate-mapping>

IdCard.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 package="domain"> <class name="IdCard" table="id_card"> <id name="id"> <generator class="foreign"> <param name="property">person</param> </generator> </id> <property name="usefulLife" column="userful_life"></property> <one-to-one name="person" constrained="true"></one-to-one> </class> </hibernate-mapping>

test.java

import java.util.Date; import domain.IdCard; import domain.Person; import hibernate.HibernateUtil; public class test { /** * @param args */ public static void main(String[] args) { IdCard idCard = new IdCard(); idCard.setUsefulLife(new Date()); Person p = new Person(); p.setName("pf"); p.setIdCard(idCard); idCard.setPerson(p); HibernateUtil.add(p); HibernateUtil.add(idCard); } }

发现一对一关系中

p.setIdCard(idCard);
idCard.setPerson(p);

相互都设置了关联，但是去掉第一行代码，程序仍能正常运行，而相反删去第二行代码，程序报错。

是存在主从表关系，可以仅保存主对象，但是不可以只保存从对象不保存主对象。