hibernate 关系映射之 主键关联一对一

单向双向在数据库中没有区别，但是在java程序中有区别。

 

在程序中：双向的通过一个就可以找到另一个，单向的通过设置了对应关系的类可以找到它所对应的类，反过来就不行。

 

注解方式单向主键关联：

和外键一样，只不过注解由@JoinColumn变成@PrimaryKeyJoinColumn

 

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 String getName() {
        return name;
    }
    @OneToOne
    @PrimaryKeyJoinColumn
    public Wife getWife() {
        return wife;
    }
    public void setId(int id) {
        this.id = id;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setWife(Wife wife) {
        this.wife = wife;
    }
   
}

 

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;
    }
   
}

xml方式单向主键关联：

<?xml version="1.0"?>
<!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.test.hibernate.StuIdCard">
        <id name="id">
            <generator class="foreign">
               <param name="property">student</param><!--   根据外键生成该字段 -->
            </generator>
        </id>
       
        <property name="num"/>
        <one-to-one name="student" constrained="true"></one-to-one>
    </class>
   
</hibernate-mapping>

 

 

注解方式双向主键关联：

给Wife类追加以下内容

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 Wife {
    private int id;
    private String name;
    private Husband husband;
    @OneToOne
    @PrimaryKeyJoinColumn
    public Husband getHusband() {
        return husband;
    }
    public void setHusband(Husband husband) {
        this.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;
    }
   
}

 

xml方式主键双向关联：

public class Student {
   
    private int id;
    private String name;
   
    private int age;
    private String sex;
    private boolean good;
    private StuIdCard stuIdCard;
    public StuIdCard getStuIdCard() {
        return stuIdCard;
    }
    public void setStuIdCard(StuIdCard stuIdCard) {
        this.stuIdCard = stuIdCard;
    }
    public boolean isGood() {
        return good;
    }
    public void setGood(boolean good) {
        this.good = good;
    }
    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 int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public String getSex() {
        return sex;
    }
    public void setSex(String sex) {
        this.sex = sex;
    }
}

 

 

<?xml version="1.0"?>
<!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.bjsxt.hibernate.Student" dynamic-update="true">
        <id name="id">
            <generator class="native"></generator>
        </id>
       
        <property name="name"></property>
        <property name="age" />
        <property name="sex" />
        <property name="good" type="yes_no"></property>
        <one-to-one name="stuIdCard" property-ref="student"></one-to-one>
    </class>
   
</hibernate-mapping>