036：一对一单向外键关联（在xml中）

可以用Student和StuIdCard来举例：

1、Student.java类：

package com.bjsxt.hibernate;

public class Student {
	
	private int id;
	private String name;
	
	private int age;
	private String sex;
	private boolean good;
	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;
	}
	
	
	
}

2.Student.hbm.xml中：

<?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>
    </class>
	
</hibernate-mapping>

3、建StuIdCard.java

package com.bjsxt.hibernate;

public class StuIdCard {
	private int id;
	private String num;
	private Student student;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getNum() {
		return num;
	}
	public void setNum(String num) {
		this.num = num;
	}
	public Student getStudent() {
		return student;
	}
	public void setStudent(Student student) {
		this.student = student;
	}
	
}

4、建相应的xml文件：StuIdCard.hbm.xml

<?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.StuIdCard">
		<id name="id">
			<generator class="native"></generator>
		</id>
		
		<property name="num"/>
		<many-to-one name="student" column="studentId" unique="true"></many-to-one>
    </class>
	
</hibernate-mapping>

5、<many-to-one name="student" column="studentId" unique="true"></many-to-one>

这句话意思为多对一，如果站在StuIdCard的方面，many-to-one意味多个学生证对应一个学生，因不是一对一，所以后面加了个unique="true"即保证IdCard的唯一，这样就变成一对一的单向关联了，column="studentId"即用column来定义用哪个字段作为外键关联 的字段。

6、在hibernate.cfg.xml中加入：

         <mapping resource="com/bjsxt/hibernate/Student.hbm.xml"/>
         <mapping resource="com/bjsxt/hibernate/StuIdCard.hbm.xml"/>

（编辑：李大同）

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