Hibernate基于主键的一对一关系----单向双向

素颜马尾好姑娘i 2022-06-12 06:47 186阅读 0赞

hibernate基于主键的一对一关系，有两种，单向和双向。基于主键的一对一关系指的是，两张表使用的是同一个id。

# 现在先说说单向 #

新建一个java项目，名称是：15hibernate\_single\_one\_to\_one\_primary

结构如下：

![Center][]

需要的jar包和如何从hibernate上获得jar包，请参见《[Hibernate环境搭建和配置][Hibernate]》

实体类IdCard、Person、HibernateUtil、hibernate.cfg.xml和hibernateTest ，

请参见《[*hibernate基于外键的一对一映射--单向和双向*][hibernate_--]》

IdCard.hbm.xml配置文件代码：

<?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="com.robert.pojo">
    	<class name="IdCard">
    		<id name="id">
    			<generator class="native"></generator>
    		</id>
    		<property name="code"></property>
    	</class>
    </hibernate-mapping>

Person.hbm.xml配置文件代码：

<?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="com.robert.pojo">
    	<class name="Person">
    		<id name="id">
         		
    			<generator class="foreign">
    				
    				<param name="property">idCard</param>
    			</generator>
    		</id>
    		<property name="name"></property>
    		<property name="age"></property>
    		
    		<one-to-one name="idCard" constrained="true" cascade="save-update" />
    
    	</class>
    </hibernate-mapping>

使用Junit4运行testCreateDB，重新生成数据库表。

alter table Person 
            drop 
            foreign key FK_3blpx78aucutb5umaelf9essh
    
        drop table if exists IdCard
    
        drop table if exists Person
    
        create table IdCard (
            id integer not null auto_increment,
            code varchar(255),
            primary key (id)
        )
    
        create table Person (
            id integer not null,
            name varchar(255),
            age integer,
            primary key (id)
        )
    
        alter table Person 
            add constraint FK_3blpx78aucutb5umaelf9essh 
            foreign key (id) 
            references IdCard (id)

testSave（）方法代码：

/**
    	 * 保存数据
    	 * 
    	 * @throws HibernateException
    	 * @throws SerialException
    	 * @throws SQLException
    	 * @throws IOException
    	 */
    	@Test
    	public void testSave() throws HibernateException, SerialException,
    			SQLException, IOException {
    		Session session = null;
    		Transaction tx = null;
    		try {
    			session = HibernateUtil.getSession();
    			tx = session.beginTransaction();
    
    			IdCard idCard = new IdCard() ;
    			idCard.setCode("1525271000000000000") ;
    			
    			Person person = new Person() ;
    			person.setAge(23) ;
    			person.setName("张三") ;
    			person.setIdCard(idCard) ;
    
    			session.save(person) ;
    			
    			IdCard idCard2 = new IdCard() ;
    			idCard2.setCode("11011010000000000") ;
    			
    			Person person2 = new Person() ;
    			person2.setAge(24) ;
    			person2.setName("李四") ;
    			person2.setIdCard(idCard2) ;
    			
    			session.save(person2);
    			
    //			Person person3 = new Person() ;
    //			person3.setAge(25) ;
    //			person3.setName("王五") ;
    //			person3.setIdCard(idCard2) ;//依然使用idCard2身份信息
    //			
    //			session.save(person3) ;
    
    			tx.commit();
    
    		} catch (HibernateException e) {
    			if (tx != null) {
    				tx.rollback();
    			}
    			e.printStackTrace();
    			throw e;
    		} finally {
    			HibernateUtil.closeSession();
    		}
    	}

控制台打印的sql语句如：

Hibernate: 
        insert 
        into
            IdCard
            (code) 
        values
            (?)
    Hibernate: 
        insert 
        into
            Person
            (name, age, id) 
        values
            (?, ?, ?)
    Hibernate: 
        insert 
        into
            IdCard
            (code) 
        values
            (?)
    Hibernate: 
        insert 
        into
            Person
            (name, age, id) 
        values
            (?, ?, ?)

==================================================================================

# 接下来是多向的 #

项目结构和大部分内容和上面是一样的，只有两个地方不一样，那就是

IdCard实体类，里面关联了Person属性，如：

package com.robert.pojo;
    
    public class IdCard {
    
    	private int id ;
    	private String code ;//身份证号 
    	private Person person ;//关联person
    	
    	public Person getPerson() {
    		return person;
    	}
    	public void setPerson(Person person) {
    		this.person = person;
    	}
    	public int getId() {
    		return id;
    	}
    	public void setId(int id) {
    		this.id = id;
    	}
    	public String getCode() {
    		return code;
    	}
    	public void setCode(String code) {
    		this.code = code;
    	}
    }

对应的IdCard.hbm.xml代码也有多不同，

<?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="com.robert.pojo">
    	<class name="IdCard">
    		<id name="id">
    			<generator class="native"></generator>
    		</id>
    		<property name="code"></property>
    		<one-to-one name="person" constrained="true" />
    	</class>
    </hibernate-mapping>

至于为什么是这么写，不用记，从文档中可以找到，如图：  
![Center 1][]

[Center]: /images/20220612/d47c0d97e39c4451ae2c2dc59d761325.png
[Hibernate]: http://blog.csdn.net/u011159417/article/details/75014665
[hibernate_--]: http://blog.csdn.net/u011159417/article/details/75232764
[Center 1]: /images/20220612/55d2d64c39004649afc93546887e8e19.png