hibernate------one-to-one

hibernate 关系映射 one-to-one主要有三种实现方式
1.通过外键方式实现
以学生和电脑为例(Student-Computer)
建表sql语句：

CREATE DATABASE `onetoone`
CHARACTER SET 'utf8';

USE `onetoone`;

DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

DROP TABLE IF EXISTS `computer`;
CREATE TABLE `computer` (
  `id` int(11) NOT NULL auto_increment,
  `name` varchar(255) NOT NULL,
  `student_id` int(11) ,
  foreign key (`student_id`) references student(`id`),
  PRIMARY KEY  (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Student.java:

package com.domain;


public class Student implements java.io.Serializable {

	private Integer id;

	private String name;

	private Computer computer;

	public Student() {
	}

	public Student(String name) {
		this.name = name;
	}

	public Integer getId() {
		return this.id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public String getName() {
		return this.name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public Computer getComputer() {
		return computer;
	}

	public void setComputer(Computer computer) {
		this.computer = computer;
	}

	
}

Computer.java:

package com.domain;

public class Computer implements java.io.Serializable {

	private Integer id;

	private Student student;

	private String name;


	public Computer() {
	}


	public Computer(String name) {
		this.name = name;
	}


	public Computer(Student student, String name) {
		this.student = student;
		this.name = name;
	}

	public Integer getId() {
		return this.id;
	}

	public void setId(Integer id) {
		this.id = id;
	}

	public Student getStudent() {
		return this.student;
	}

	public void setStudent(Student student) {
		this.student = student;
	}

	public String getName() {
		return this.name;
	}

	public void setName(String name) {
		this.name = name;
	}

}

Student.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>
    <class name="com.domain.Student" table="student" catalog="onetoone">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="native" />
        </id>
        <property name="name" type="java.lang.String">
            <column name="name" not-null="true" />
        </property>
        <!-- class可以不写，因为根据name的值computer(属性)，会通过反射自动找到属于哪个类的 -->
        <one-to-one cascade="delete,save-update" name="computer" class="com.domain.Computer" property-ref="student"></one-to-one>
    </class>
</hibernate-mapping>

Computer.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>
    <class name="com.domain.Computer" table="computer" catalog="onetoone">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="native" />
        </id>
       
        <property name="name" type="java.lang.String">
            <column name="name" not-null="true" />
        </property>
        
         <!-- many开头的是代表该表持有外键 -->
        <many-to-one  name="student" class="com.domain.Student"  unique="true">
            <column name="student_id" />
        </many-to-one>
    </class>
</hibernate-mapping>

测试类：

package com.domain;

import org.hibernate.Query;
import org.hibernate.Session;

import com.util.HibernateSessionFactory;

public class Test {
	
	public static void main(String[] args){
		Session session = HibernateSessionFactory.getSession();
		
		//save
		Student student = new Student();
		student.setName("student9");
		
		Computer computer = new Computer();
		computer.setName("Intel 9");
		
		//computer.setStudent(student)和student.setComputer(computer);都必须要
		computer.setStudent(student);
		student.setComputer(computer);
		
		session.save(student);
		
		/**
		 执行的sql:
		 Hibernate: insert into onetoone.student (name) values (?)
		 Hibernate: insert into onetoone.computer (name, student_id) values (?, ?)
		 */
		
//		
		session.beginTransaction().commit();
		
		//query
		
//		String hql = "from Student where name=?";
//		Query query = session.createQuery(hql);
//		query.setString(0, "student3");
//		
//		Student student = (Student)query.uniqueResult();
//		System.out.println(student.getId() + " : " + student.getComputer().getName());
		
		
		//delete
//		Student student = (Student)session.load(Student.class, new Integer(1));
//		session.delete(student);
//		session.beginTransaction().commit();
		
		/**
		 执行的sql为：
	Hibernate: select student0_.id as id0_1_, student0_.name as name0_1_, computer1_.id as id1_0_, computer1_.name as name1_0_, computer1_.student_id as student3_1_0_ from onetoone.student student0_ left outer join onetoone.computer computer1_ on student0_.id=computer1_.student_id where student0_.id=?
	Hibernate: delete from onetoone.computer where id=?
	Hibernate: delete from onetoone.student where id=?
		 */
		
		
		session.close();
	}

}

2.通过主键方式实现(一个表的主键由另一个表的主键决定)，在这里Computer的主键由Student的主键决定。
Student.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>
    <class name="com.domain.Student" table="student" catalog="onetoone">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <generator class="native" />
        </id>
        <property name="name" type="java.lang.String">
            <column name="name" not-null="true" />
        </property>
        <!-- class可以不写，因为根据name的值computer(属性)，会通过反射自动找到属于哪个类的 
        <one-to-one cascade="delete,save-update" name="computer" class="com.domain.Computer" property-ref="student"></one-to-one>
    	-->
    	<one-to-one name="computer"/>
    </class>
</hibernate-mapping>

Comuter.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>
    <class name="com.domain.Computer" table="computer" catalog="onetoone">
        <id name="id" type="java.lang.Integer">
            <column name="id" />
            <!--generator class="native" /-->
            
            <!--Computer的主键由Student的主键决定，可以看成是外键-->
            <generator class="foreign">
            	<param name="property">student</param>
            </generator>
        </id>
       
        <property name="name" type="java.lang.String">
            <column name="name" not-null="true" />
        </property>
        
         <!-- many开头的是代表该表持有外键
        <many-to-one  name="student" class="com.domain.Student"  unique="true">
            <column name="student_id" />
        </many-to-one> -->
        <one-to-one name="student"/>
    </class>
</hibernate-mapping>

TestMainKey.java:

package com.domain;

import org.hibernate.Session;

import com.util.HibernateSessionFactory;

public class TestMainKey {

	public static void main(String[] args){
		Session session = HibernateSessionFactory.getSession();
		
		//save
		Student student = new Student();
		student.setName("student15");
		
		Computer computer = new Computer();
		computer.setName("Intel 15");
		
		
		computer.setStudent(student);
//		student.setComputer(computer);
		//因为save 2个表，所以不需要双向赋值
		session.save(student);
		session.save(computer);
		
		session.beginTransaction().commit();
		session.close();
	}
}

3.通过关系表实现：

DROP TABLE IF EXISTS `st`;
create table stu_com(
	stu_id int not null,
	com_id int not null
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

<!--optional="true"的意思是只有当stu_id 和 com_id 都不为空时才在关系表里插入。这样也会插入

2遍，所以需要inverse="true"把一方设置为虚的。即不让插入到关系表中-->
<join table="stu-com" optional="true" inverse="true">
	<key column="com_id"/>
	<many-to-one name="student" column="stu_id" unique="true"/>
</join>

评论

2 楼 gaolegao2008 2011-07-14  

版主写的好

1 楼 stevenzuo 2009-02-10  

楼主写的经典呀！