hibernate多对多例子-优快云博客

本文介绍了一个使用Hibernate实现的多对多关系映射的例子，包括创建学生和课程之间的关联表，定义Java实体类，编写Hibernate配置文件，并提供创建记录和查询记录的测试类。

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hibernate多对多例子-方便以后查看(三)

1.建表

create table student

(sid varchar ( 32 ) not null primary key ,

sname varchar ( 16 ),

sage varchar ( 16 ),

)

create table course

(cid varchar ( 32 ) not null primary key ,

cname varchar ( 16 )

)

create table student_course_link

(sid varchar ( 32 ) not null ,

cid varchar ( 32 ) not null ,

primary key (sid,cid)

)

2.写VO
StudentVO

package com.test;

import java.util.Set;

public class Student

{

private String sid;

private String sname;

private String sage;

private Set course;

public Student()

{

}

// 写上get set

Course vo

package com.test;

import java.util.Set;

public class Course

{

private String cid;

private String cname;

private Set student;

// 写上get set

写配置文件
Student.hbm.xml

<? xml version="1.0" ?>

<! DOCTYPE hibernate-mapping

PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >

< hibernate-mapping >

< class name ="com.test.Student" table ="student" >

< id name ="sid" type ="string" unsaved-value ="null" >

< column name ="sid" sql-type ="char(32)" not-null ="true" />

< generator class ="uuid.hex" />

</ id >

< property name ="sname" >

< column name ="sname" sql-type ="varchar(16)" not-null ="true" />

</ property >

< property name ="sage" >

< column name ="sage" sql-type ="varchar(16)" not-null ="true" />

</ property >

< set name ="course" table ="student_course_link" cascade ="all" outer-join ="false" >

< key column ="sid" />

< many-to-many class ="com.test.Course" column ="cid" />

</ set >

</ class >

</ hibernate-mapping >

Course.hbm.xml

<? xml version="1.0" ?>

<! DOCTYPE hibernate-mapping

PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >

< hibernate-mapping >

< class name ="com.test.Course" table ="course" >

< id name ="cid" type ="string" unsaved-value ="null" >

< column name ="cid" sql-type ="char(32)" not-null ="true" />

< generator class ="uuid.hex" />

</ id >

< property name ="cname" >

< column name ="cname" sql-type ="varchar(16)" not-null ="true" />

</ property >

< set name ="student" table ="student_course_link" lazy ="false" cascade ="all" >

< key column ="cid" />

< many-to-many class ="com.test.Student" column ="sid" />

</ set >

</ class >

</ hibernate-mapping >

接着把下面的hibernate.properties文件拷到classes目录下。。这里用的是mysql

hibernate.query.substitutions true 1, false 0, yes 'Y', no 'N'

## MySQL

hibernate.dialect net.sf.hibernate.dialect.MySQLDialect

hibernate.connection.driver_class org.gjt.mm.mysql.Driver

hibernate.connection.url jdbc:mysql://localhost:3306/wjcms

hibernate.connection.username root

hibernate.connection.password wujun

hibernate.connection.pool_size 1

hibernate.proxool.pool_alias pool1

hibernate.show_sql true

hibernate.jdbc.batch_size 0

hibernate.max_fetch_depth 1

hibernate.cache.use_query_cache true

写测试类了..

package com.test;

import net.sf.hibernate.Session;

import net.sf.hibernate.SessionFactory;

import net.sf.hibernate.cfg.Configuration;

import net.sf.hibernate. * ;

import java.util.Set;

import java.util.HashSet;

import java.sql. * ;

import java.util.List;

import java.util.Iterator;

public class TestManyToMany

{

SessionFactory sf;

Session session;

public TestManyToMany()

{

try

{

Configuration cfg = new Configuration();

sf = cfg.addClass(Student. class ).addClass(Course. class ).buildSessionFactory();

}

catch (HibernateException ex)

{

ex.printStackTrace();

}

public void doCreate()

{

try

{

session = sf.openSession();

Student student = new Student();

student.setSname( " 小王 " );

student.setSage( " 22 " );

Set courseSet = new HashSet();

Course course = null ;

for ( int i = 0 ;i < 2 ;i ++ )

{

course = new Course();

if (i == 0 )

course.setCname( " c++ " );

else if (i == 1 )

course.setCname( " java " );

courseSet.add(course);

}

student.setCourse(courseSet);

session.save(student);

session.flush();

session.connection().commit();

}

catch (HibernateException ex)

{

ex.printStackTrace();

}

catch (SQLException ex1)

{

ex1.printStackTrace();

}

finally

{

try {

session.close();

}

catch (HibernateException ex2) {

}

public void doQuery()

{

try {

session = sf.openSession();

Query q = session.createQuery( " select s from Student as s " );

List l = q.list();

Student s = null ;

Course course = null ;

for ( int i = 0 ;i < l.size();i ++ )

{

s = (Student)l.get(i);

System.out.println( " 姓名： " + s.getSname());

System.out.println( " 年龄： " + s.getSage());

System.out.println( " 所选的课程： " );

Iterator it = s.getCourse().iterator();

while (it.hasNext())

{

course = (Course)it.next();

System.out.println( " 课程名： " + course.getCname());

}

catch (HibernateException ex) {

ex.printStackTrace();

}

finally {

try {

session.close();

}

catch (HibernateException ex2) {

}

public static void main(String[] args)

{

TestManyToMany t = new TestManyToMany();

// t.doCreate();

t.doQuery();

}

好。。可以了。。