Hibernate之one-to-one外键关联映射详解编程语言

在hibernate一对一实体映射中，常用有两种方式，一种就是把一对一看作多对一的一个特例，即通过外键参考。

另一种是通过主键参考，限制两个数据表中的主键使用相同的值。

po类

Person.java

package po; 

public class Person { 

 private int id; 

 private String name; //姓名 

 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; 

Card.java

package po; 

public class Card { 

 private int id; //身份证ID 

 private String number; //身份证号码 

 private Person person; //一个身份证号对应一个人 

 public int getId() { 

 return id; 

 public void setId(int id) { 

 this.id = id; 

 public String getNumber() { 

 return number; 

 public void setNumber(String number) { 

 this.number = number; 

 public Person getPerson() { 

 return person; 

 public void setPerson(Person person) { 

 this.person = person; 


 property name="number" /property 

 !-- 是多对一的一种特例 unique=true设置为唯一关联 -- 

 many-to-one name="person" unique="true" column="person" /many-to-one 

 /class 

 /hibernate-mapping 

Person.hbm.xml

 hibernate-mapping 

 class name="po.Person" table="person" 

 id name="id" type="integer" 

 generator / 

 /id 

 property name="name" / 

 /class 

 /hibernate-mapping 

hibernate.cfg.xml

 hibernate-configuration 

 session-factory 

 property name="dialect" org.hibernate.dialect.MySQLDialect /property 

 property name="connection.url" jdbc:mysql://localhost:3306/hibernate /property 

 property name="connection.username" root /property 

 property name="connection.password" 1 /property 

 property name="connection.driver_class" com.mysql.jdbc.Driver /property 

 property name="myeclipse.connection.profile" mysql /property 

 property name="show_sql" true /property 

 property name="format_sql" true /property 

 mapping resource="po/Person.hbm.xml"/ 

 mapping resource="po/Card.hbm.xml"/ 

 /session-factory 

 /hibernate-configuration 

Test.java

package po; 

import java.util.Date; 

import java.util.HashSet; 

import java.util.Iterator; 

import java.util.Set; 

import org.hibernate.Session; 

import org.hibernate.SessionFactory; 

import org.hibernate.cfg.Configuration; 

import org.hibernate.tool.hbm2ddl.SchemaExport; 

import org.junit.Test; 


 Configuration config = new Configuration().configure(); 

 SchemaExport export = new SchemaExport(config); 

 export.create(true, true); 

 @Test 

 public void testSave(){ 

 //测试 添加数据 

 Configuration config = new Configuration().configure(); 

 SessionFactory factory = config.buildSessionFactory(); 

 Session session = factory.openSession(); 

 session.beginTransaction(); 


 Person person = new Person(); //先有person然后才能有省份证 

 person.setName("zhangsan"); 

 session.save(person); //一对一外键关联时 必须先保存person 


 public void testGetPerson(){ 

 Configuration config = new Configuration().configure(); 

 SessionFactory factory = config.buildSessionFactory(); 

 Session session = factory.openSession(); 

 session.beginTransaction(); 

 Card card = (Card)session.get(Card.class,2 ); //取出Card 

 System.out.println("CardNumber: "+card.getNumber()); 

 Person person = card.getPerson(); //通过card.getPerson()方法 返回person 

 System.out.println("PersonName: "+person.getName()); //取出person的name 

 session.getTransaction().commit(); 

 session.close(); 

person和card分别生成sql为：

| card | CREATE TABLE `card` ( 

 `id` int(11) NOT NULL auto_increment, 

 `number` varchar(255) default NULL, 

 `person` int(11) default NULL, 

 PRIMARY KEY (`id`), 

 UNIQUE KEY `person` (`person`), 

 KEY `FK2E7B10BD1DCD99` (`person`), 

 CONSTRAINT `FK2E7B10BD1DCD99` FOREIGN KEY (`person`) REFERENCES `person` (`id`) 

) ENGINE=InnoDB DEFAULT CHARSET=utf8 |