码迷，mamicode.com
首页 > Web开发 > 详细

hibernate（六）一对一映射

时间：2015-12-21 23:30:15      阅读：213      评论：0      收藏：0      [点我收藏+]

标签：

关系映射是指对象之间的关系，并不是指数据库的关系，关系映射是解决当对象处于以下关系之一时，数据库表该如何映射的问题

(一)一对一单向外键关联

1、注解方式配置

创建一个Husband类和Wife类

Husband类:(getWife方法上加注解OneToOne)

package cn.orlion.hibernate.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Husband {
    
    private int id;
    
    private String name;
    
    private Wife wife;
    
    @Id
    @GeneratedValue
    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;
    }
    @OneToOne
　　@JoinColumn(name="wifeId")//默认生成的外键id是wife_id在这里使用JoinColumn注解name属性指定为wifeId
    public Wife getWife() {
        return wife;
    }

    public void setWife(Wife wife) {
        this.wife = wife;
    }
}

Wife类

package cn.orlion.hibernate.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;

@Entity
public class Wife {

    private int id;
    
    private String name;
    
    @Id
    @GeneratedValue
    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;
    }
}

然后创建一个测试类HibernateMappingTest

package cn.orlion.hibernate.model;

import org.hibernate.cfg.AnnotationConfiguration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

import org.junit.Test;

public class HibernateORMappingTest {

    @Test
    public void testSchemaExport(){
        
        new SchemaExport(new AnnotationConfiguration().configure()).create(true , true);
    }

}

运行testSchemaExport可以在控制台看到建表语句:

技术分享

 

2、xml方式配置

首先创建一个Student类和StuIdCard(学生证)

Student类：

package cn.orlion.hibernate.model;

public class Student {

    private int id;
    
    private String name;
    
    private String sex;

    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 String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }
}

StuIdCard：

package cn.orlion.hibernate.model;

public class StuIdCard {

    private int id;
    
    private int num;
    
    private Student student;

    public int getId() {
        return id;
    }

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

    public int getNum() {
        return num;
    }

    public void setNum(int num) {
        this.num = num;
    }

    public Student getStudent() {
        return student;
    }

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

然后创建两个配置文件Student.hbm.xml：

<?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="cn.orlion.hibernate.model">
    <class name="cn.orlion.hibernate.model.Student">
        <id name="id">
            <generator class="native"></generator>
        </id>
        
        <property name="name"></property>
        
        <property name="sex"></property>
    </class>
</hibernate-mapping>

StuIdCard.hbm.xml：

<?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="cn.orlion.hibernate.model">
    <class name="cn.orlion.hibernate.model.StuIdCard">
        <id name="id">
            <generator class="native"></generator>
        </id>
        
        <property name="num" />
        
        <many-to-one name="student" column="studentId" unique="true"></many-to-one>
        <!-- many-to-one是当前类即StuIdCard类相对于Student类是多对一关系 （多个学生证对应一个学生） ，unique=true限定为了一对一 -->
    </class>
</hibernate-mapping>

然后运行测试类HibernateORMappingTest类的testSchemaExport方法可以在控制台看到建表语句:

技术分享

技术分享

(二)一对一双向外键关联

1、注解方式设置

双向外键关联注解方式设置是在wife类中添加husband属性，在getHusband()方法上添加注解@OneToOne(mappedBy="wife")//mappedBy="wife"表示Husband中wife属性已经做映射了，不用管当前类的设置（不再从wife表中生成指向husband的外键）注:如果不写mappedBy="wife"会在wife表中生成一个husband_id外键，这是多余的。

Wife类：

package cn.orlion.hibernate.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Wife {

    private int id;
    
    private String name;
    
    private Husband husband;
    
    @Id
    @GeneratedValue
    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;
    }
    @OneToOne(mappedBy="wife")//mappedBy="wife"表示Husband中wife属性已经做映射了，不用管当前类的设置（不再从wife表中生成指向husband的外键）
    public Husband getHusband() {
        return husband;
    }

    public void setHusband(Husband husband) {
        this.husband = husband;
    }
    
}

2、xml方式配置
在Student.hbm.xml配置文件中添加<one-to-one name="stuIdCard" property-ref="student"></one-to-one>，在Student类中添加stuIdCard属性：

Student类：

package cn.orlion.hibernate.model;

public class Student {

    private int id;
    
    private String name;
    
    private String sex;
    
    private StuIdCard stuIdCard;

    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 String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public StuIdCard getStuIdCard() {
        return stuIdCard;
    }

    public void setStuIdCard(StuIdCard stuIdCard) {
        this.stuIdCard = stuIdCard;
    }
    
}

Student.hbm.xml:

<?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="cn.orlion.hibernate.model">
    <class name="cn.orlion.hibernate.model.Student">
        <id name="id">
            <generator class="native"></generator>
        </id>
        
        <property name="name"></property>
        
        <property name="sex"></property>
        
        <one-to-one name="stuIdCard" property-ref="student"></one-to-one>
        <!-- one-to-one只会在一边生成主键，如果这里设置为many-to-one会在student表中生成多余的stuidcard_id外键 -->
        <!-- property-ref="student" 类似于mappedby="student"是指在StuIdCard中student属性已经设置好了关联关系 -->
    </class>
</hibernate-mapping>

注：一对一单向和双向在数据库中表现没有区别

 

主键关联是指的一个表的主键和另外一个表的主键关联
外键关联是指的一个表的主键和另外一个表的非主键关联

 

（三）一对一单向主键关联

xml方式配置：

创建Student类

package cn.orlion.hibernate.model;

public class Student {

    private int id;
    
    private String name;
    
    private String sex;

    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 String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }
}

StuIdCard类：

package cn.orlion.hibernate.model;

public class StuIdCard {

    private int id;
    
    private int num;
    
    private Student student;

    public int getId() {
        return id;
    }

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

    public int getNum() {
        return num;
    }

    public void setNum(int num) {
        this.num = num;
    }

    public Student getStudent() {
        return student;
    }

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

Student.hbm.xml:

<?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="cn.orlion.hibernate.model">
    <class name="cn.orlion.hibernate.model.Student">
        <id name="id">
            <generator class="native"></generator>
        </id>
        
        <property name="name"></property>
        
        <property name="sex"></property>
    </class>
</hibernate-mapping>

StuIdCard.hbm.xml:

<?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="cn.orlion.hibernate.model">
    <class name="cn.orlion.hibernate.model.StuIdCard">
        <id name="id">
            <generator class="foreign"><!-- StuIdCard的主键应该靠外键来生成，StuIdCard -->
                <param name="property">student</param><!-- 依靠student属性的关联关系 -->
            </generator>
        </id>
        
        <property name="num" />
        
        <one-to-one name="student" constrained="true"></one-to-one>
        <!-- constrained="true"用来生成外键约束，不加这个属性就不会加外键 -->
    </class>
</hibernate-mapping>

 

运行：

技术分享

（四）一对一双向主键关联

注解方式配置:

Husband类：

package cn.orlion.hibernate.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;

@Entity
public class Husband {
    
    private int id;
    
    private String name;
    
    private Wife wife;
    
    @Id
    @GeneratedValue
    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;
    }
    @OneToOne
    @PrimaryKeyJoinColumn
    public Wife getWife() {
        return wife;
    }

    public void setWife(Wife wife) {
        this.wife = wife;
    }
}

 

Wife类：

package cn.orlion.hibernate.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entity
public class Wife {

    private int id;
    
    private String name;
    
    private Husband husband;
    
    @Id
    @GeneratedValue
    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;
    }
    @OneToOne
    @PrimaryKeyJoinColumn
　　 public Husband getHusband() {
        return husband;
    }

    public void setHusband(Husband husband) {
        this.husband = husband;
    }
    
}

 

（五）联合主键映射

Wife类：

package cn.orlion.hibernate.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.IdClass;

@Entity
@IdClass(WifePK.class)
public class Wife {

    private int id;
    
    private String name;
    
    private String age;
    
    @Id
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }
    @Id
    public String getName() {
        return name;
    }

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

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }
    
}

WifePK：

package cn.orlion.hibernate.model;

public class WifePK {

    private int id;
    
    private String name;
    
    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;
    }
}

Husband类：

package cn.orlion.hibernate.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinColumns;
import javax.persistence.OneToOne;

@Entity
public class Husband {
    
    private int id;
    
    private String name;
    
    private Wife wife;
    
    @Id
    @GeneratedValue
    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;
    }
    @OneToOne
    @JoinColumns(
        {
            @JoinColumn(name="wifeId" , referencedColumnName="id"),
            @JoinColumn(name="wifeName" , referencedColumnName="name")
        }    
    )
    public Wife getWife() {
        return wife;
    }

    public void setWife(Wife wife) {
        this.wife = wife;
    }
}

运行结果：

技术分享

hibernate（六）一对一映射

标签：

原文地址：http://www.cnblogs.com/orlion/p/5065189.html
踩
(0)
赞
(0)
   
举报
评论 一句话评论（0）
登录后才能评论！
分享档案
更多>
2021年07月29日 (22)
2021年07月28日 (40)
2021年07月27日 (32)
2021年07月26日 (79)
2021年07月23日 (29)
2021年07月22日 (30)
2021年07月21日 (42)
2021年07月20日 (16)
2021年07月19日 (90)
2021年07月16日 (35)
周排行
mamicode.com排行更多图片
更多
友情链接
兰亭集智   国之画   百度统计   站长统计   阿里云   chrome插件   新版天听网
关于我们 - 联系我们 - 留言反馈
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码！