hibernate 之 9.one2one双向

在培训系统中,我们经常会为每一个学员，分配一个所属登录帐号,对应的表结构设计如下:

图1:培训系统表结构

t_student:

学员信息表,存储学员的基本信息，如：姓名、年龄、身份证号、地址等等

t_user:

用户表，储系统用户信息,如:登录帐号、密码等

从图1中，知道 它通过student_id来关联 t_studnet

面向对象类关系

配置:

User类

package com.demo.model;

/**用户信息
 * @author wobendiankun
 *2014-10-29 下午11:05:26
 */
public class User {
	/**
	 *用户Id 
	 */
	private int userId;
	/**
	 * 用户名
	 */
	private String userName;
	/**
	 * 密码
	 */
	private String password;
	
	private Student student ;
	
	
	public int getUserId() {
		return userId;
	}
	public void setUserId(int userId) {
		this.userId = userId;
	}
	public String getUserName() {
		return userName;
	}
	public void setUserName(String userName) {
		this.userName = userName;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public Student getStudent() {
		return student;
	}
	public void setStudent(Student student) {
		this.student = student;
	}
	
}

Student类

package com.demo.model;

import java.io.UnsupportedEncodingException;
import java.util.Set;

/**学生信息
 * @author wobendiankun
 *2014-10-19 下午08:54:29
 */
public class Student {
	private int studentId ;
	private String studentName ;
	private int age;
	private Set<Certificate> certificates ;
	private User user;
	public int getStudentId() {
		return studentId;
	}
	public void setStudentId(int studentId) {
		this.studentId = studentId;
	}
	public String getStudentName() {
		return studentName;
	}
	public void setStudentName(String studentName) {
		this.studentName = studentName;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	@Override
	public String toString() {
		String str="";
		if(studentName!=null){
			try {
				str=new String(studentName.getBytes("UTF-8"));
			} catch (UnsupportedEncodingException e) {
				e.printStackTrace();
			}
		}
		return "Student [studentId=" + studentId + ", studentName="
				+ str + ", age=" + age + "]";
	}
	public Set<Certificate> getCertificates() {
		return certificates;
	}
	public void setCertificates(Set<Certificate> certificates) {
		this.certificates = certificates;
	}
	public User getUser() {
		return user;
	}
	public void setUser(User user) {
		this.user = user;
	}
	
}

User.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.demo.model.User" table="t_user">
		<id name="userId" column="user_id">
			<generator class="sequence">
				<param name="sequence">SEQ_T_USER</param>
			</generator>
		</id>
		<property name="userName" column="user_name" />
		<property name="password" />
		<many-to-one name="student" column="student_id" unique="true">
		</many-to-one>
	</class>
</hibernate-mapping>

<many-to-one name="student" column="student_id" unique="true"> ,通过 unique="true" 来说明1对1关系，并由这方来维护关联字段

Student.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.demo.model.Student" table="t_student">
		<id name="studentId" column="student_id">
			<generator class="sequence">
				<param name="sequence">SEQ_T_STUDENT</param>
			</generator>
		</id>
		<property name="studentName" column="student_name" />
		<property name="age" />
		
		<set name="certificates" lazy="extra" inverse="true">
			<key column="student_id"></key>
			<one-to-many class="com.demo.model.Certificate"/>
		</set>
		<one-to-one name="user" property-ref="student"></one-to-one>
	</class>
</hibernate-mapping>

<one-to-one name="user" property-ref="student"></one-to-one>  ,

name为Student类的成员变量user,

property-ref为User类的成员变量student

add:

@Test
	public void addTest(){
		Student student=new Student();
		student.setStudentName("大宝");
		student.setAge(45);
		
		User user=new User();
		user.setUserName("db");
		user.setPassword("111111");
		//设置双向关系
		user.setStudent(student);
		student.setUser(user);
		
		Session session = null;
		try {
			session = HibernateUtil.openSession();
			session.beginTransaction();
			session.save(student);
			session.save(user);
			session.getTransaction().commit();
		} catch (Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			HibernateUtil.closeSession(session);
		}
	}

发出的sql:

Hibernate: insert into t_student (student_name, age, student_id) values (?, ?, ?)
Hibernate: insert into t_user (user_name, password, student_id, user_id) values (?, ?, ?, ?)

update

@Test
	public void updateTest(){
		User user=new User();
		user.setUserId(21);
		user.setUserName("dddd");
		Student student=new Student();
		student.setStudentId(102);
		student.setStudentName("二宝");
		//设置关联关系
		student.setUser(user);
		
		Session session = null;
		try {
			session = HibernateUtil.openSession();
			session.beginTransaction();
			session.update(student);
			session.getTransaction().commit();
		} catch (Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			HibernateUtil.closeSession(session);
		}
	}

发出的sql

Hibernate: update t_student set student_name=?, age=? where student_id=?

Student这方不负责维护关联字段，不会发送更新User 的语句