Hibernate one-to-one一对一映射

于 2009-03-13 12:40:00 发布
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文章标签： java 数据库
本文介绍Hibernate中一对一关系映射的三种实现方式：通过外键、主键和关系表实现。详细展示了每种方式的数据库表结构、Java实体类定义及配置文件。

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：
Java代码 复制代码
  1. CREATEDATABASE`onetoone`
  2. CHARACTERSET'utf8';
  4. USE`onetoone`;
  6. DROPTABLEIFEXISTS`student`;
  7. CREATETABLE`student`(
  8. `id`int(11)NOTNULLauto_increment,
  9. `name`varchar(255)NOTNULL,
  10. PRIMARYKEY(`id`)
  11. )ENGINE=InnoDBDEFAULTCHARSET=utf8;
  13. DROPTABLEIFEXISTS`computer`;
  14. CREATETABLE`computer`(
  15. `id`int(11)NOTNULLauto_increment,
  16. `name`varchar(255)NOTNULL,
  17. `student_id`int(11),
  18. foreignkey(`student_id`)referencesstudent(`id`),
  19. PRIMARYKEY(`id`)
  20. )ENGINE=InnoDBDEFAULTCHARSET=utf8;
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:
Java代码 复制代码
  1. packagecom.domain;
  4. publicclassStudentimplementsjava.io.Serializable{
  6. privateIntegerid;
  8. privateStringname;
  10. privateComputercomputer;
  12. publicStudent(){
  13. }
  15. publicStudent(Stringname){
  16. this.name=name;
  17. }
  19. publicIntegergetId(){
  20. returnthis.id;
  21. }
  23. publicvoidsetId(Integerid){
  24. this.id=id;
  25. }
  27. publicStringgetName(){
  28. returnthis.name;
  29. }
  31. publicvoidsetName(Stringname){
  32. this.name=name;
  33. }
  35. publicComputergetComputer(){
  36. returncomputer;
  37. }
  39. publicvoidsetComputer(Computercomputer){
  40. this.computer=computer;
  41. }
  44. }
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:
Java代码 复制代码
  1. packagecom.domain;
  3. publicclassComputerimplementsjava.io.Serializable{
  5. privateIntegerid;
  7. privateStudentstudent;
  9. privateStringname;
  12. publicComputer(){
  13. }
  16. publicComputer(Stringname){
  17. this.name=name;
  18. }
  21. publicComputer(Studentstudent,Stringname){
  22. this.student=student;
  23. this.name=name;
  24. }
  26. publicIntegergetId(){
  27. returnthis.id;
  28. }
  30. publicvoidsetId(Integerid){
  31. this.id=id;
  32. }
  34. publicStudentgetStudent(){
  35. returnthis.student;
  36. }
  38. publicvoidsetStudent(Studentstudent){
  39. this.student=student;
  40. }
  42. publicStringgetName(){
  43. returnthis.name;
  44. }
  46. publicvoidsetName(Stringname){
  47. this.name=name;
  48. }
  50. }
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:
Java代码 复制代码
  1. <?xmlversion="1.0"encoding="utf-8"?>
  2. <!DOCTYPEhibernate-mappingPUBLIC"-//Hibernate/HibernateMappingDTD3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping>
  6. <classname="com.domain.Student"table="student"catalog="onetoone">
  7. <idname="id"type="java.lang.Integer">
  8. <columnname="id"/>
  9. <generatorclass="native"/>
  10. </id>
  11. <propertyname="name"type="java.lang.String">
  12. <columnname="name"not-null="true"/>
  13. </property>
  14. <!--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-->
  15. <one-to-onecascade="delete,save-update"name="computer"class="com.domain.Computer"property-ref="student"></one-to-one>
  16. </class>
  17. </hibernate-mapping>
<?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:
Java代码 复制代码
  1. <?xmlversion="1.0"encoding="utf-8"?>
  2. <!DOCTYPEhibernate-mappingPUBLIC"-//Hibernate/HibernateMappingDTD3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping>
  6. <classname="com.domain.Computer"table="computer"catalog="onetoone">
  7. <idname="id"type="java.lang.Integer">
  8. <columnname="id"/>
  9. <generatorclass="native"/>
  10. </id>
  12. <propertyname="name"type="java.lang.String">
  13. <columnname="name"not-null="true"/>
  14. </property>
  16. <!--many开头的是代表该表持有外键-->
  17. <many-to-onename="student"class="com.domain.Student"unique="true">
  18. <columnname="student_id"/>
  19. </many-to-one>
  20. </class>
  21. </hibernate-mapping>
<?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：
Java代码 复制代码
  1. packagecom.domain;
  3. importorg.hibernate.Query;
  4. importorg.hibernate.Session;
  6. importcom.util.HibernateSessionFactory;
  8. publicclassTest{
  10. publicstaticvoidmain(String[]args){
  11. Sessionsession=HibernateSessionFactory.getSession();
  13. //save
  14. Studentstudent=newStudent();
  15. student.setName("student9");
  17. Computercomputer=newComputer();
  18. computer.setName("Intel9");
  20. //computer.setStudent(student)和student.setComputer(computer);都必须要
  21. computer.setStudent(student);
  22. student.setComputer(computer);
  24. session.save(student);
  26. /**
  27. 执行的sql:
  28. Hibernate:insertintoonetoone.student(name)values(?)
  29. Hibernate:insertintoonetoone.computer(name,student_id)values(?,?)
  30. */
  32. //
  33. session.beginTransaction().commit();
  35. //query
  37. //Stringhql="fromStudentwherename=?";
  38. //Queryquery=session.createQuery(hql);
  39. //query.setString(0,"student3");
  40. //
  41. //Studentstudent=(Student)query.uniqueResult();
  42. //System.out.println(student.getId()+":"+student.getComputer().getName());
  45. //delete
  46. //Studentstudent=(Student)session.load(Student.class,newInteger(1));
  47. //session.delete(student);
  48. //session.beginTransaction().commit();
  50. /**
  51. 执行的sql为：
  52. Hibernate:selectstudent0_.idasid0_1_,student0_.nameasname0_1_,computer1_.idasid1_0_,computer1_.nameasname1_0_,computer1_.student_idasstudent3_1_0_fromonetoone.studentstudent0_leftouterjoinonetoone.computercomputer1_onstudent0_.id=computer1_.student_idwherestudent0_.id=?
  53. Hibernate:deletefromonetoone.computerwhereid=?
  54. Hibernate:deletefromonetoone.studentwhereid=?
  55. */
  58. session.close();
  59. }
  61. }
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:
Java代码 复制代码
  1. <?xmlversion="1.0"encoding="utf-8"?>
  2. <!DOCTYPEhibernate-mappingPUBLIC"-//Hibernate/HibernateMappingDTD3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping>
  6. <classname="com.domain.Student"table="student"catalog="onetoone">
  7. <idname="id"type="java.lang.Integer">
  8. <columnname="id"/>
  9. <generatorclass="native"/>
  10. </id>
  11. <propertyname="name"type="java.lang.String">
  12. <columnname="name"not-null="true"/>
  13. </property>
  14. <!--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
  15. <one-to-onecascade="delete,save-update"name="computer"class="com.domain.Computer"property-ref="student"></one-to-one>
  16. -->
  17. <one-to-onename="computer"/>
  18. </class>
  19. </hibernate-mapping>
<?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:
Java代码 复制代码
  1. <?xmlversion="1.0"encoding="utf-8"?>
  2. <!DOCTYPEhibernate-mappingPUBLIC"-//Hibernate/HibernateMappingDTD3.0//EN"
  3. "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
  5. <hibernate-mapping>
  6. <classname="com.domain.Computer"table="computer"catalog="onetoone">
  7. <idname="id"type="java.lang.Integer">
  8. <columnname="id"/>
  9. <!--generatorclass="native"/-->
  11. <!--Computer的主键由Student的主键决定，可以看成是外键-->
  12. <generatorclass="foreign">
  13. <paramname="property">student</param>
  14. </generator>
  15. </id>
  17. <propertyname="name"type="java.lang.String">
  18. <columnname="name"not-null="true"/>
  19. </property>
  21. <!--many开头的是代表该表持有外键
  22. <many-to-onename="student"class="com.domain.Student"unique="true">
  23. <columnname="student_id"/>
  24. </many-to-one>-->
  25. <one-to-onename="student"/>
  26. </class>
  27. </hibernate-mapping>
<?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:

Java代码 复制代码
  1. packagecom.domain;
  3. importorg.hibernate.Session;
  5. importcom.util.HibernateSessionFactory;
  7. publicclassTestMainKey{
  9. publicstaticvoidmain(String[]args){
  10. Sessionsession=HibernateSessionFactory.getSession();
  12. //save
  13. Studentstudent=newStudent();
  14. student.setName("student15");
  16. Computercomputer=newComputer();
  17. computer.setName("Intel15");
  20. computer.setStudent(student);
  21. //student.setComputer(computer);
  22. //因为save2个表，所以不需要双向赋值
  23. session.save(student);
  24. session.save(computer);
  26. session.beginTransaction().commit();
  27. session.close();
  28. }
  29. }
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：
Java代码 复制代码
  1. DROPTABLEIFEXISTS`st`;
  2. createtablestu_com(
  3. stu_idintnotnull,
  4. com_idintnotnull
  5. )ENGINE=InnoDBDEFAULTCHARSET=utf8;
DROP TABLE IF EXISTS `st`;
create table stu_com(
	stu_id int not null,
	com_id int not null
)ENGINE=InnoDB DEFAULT CHARSET=utf8;

Java代码 复制代码
  1. <!--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
  3. 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-->
  4. <jointable="stu-com"optional="true"inverse="true">
  5. <keycolumn="com_id"/>
  6. <many-to-onename="student"column="stu_id"unique="true"/>
  7. </join>
<!--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>
iteye_13254
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