hibernate多对多的基础理解

转载自：http://www.blogjava.net/wujun/archive/2006/04/08/39956.html

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-mappingPUBLIC "-//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-mappingPUBLIC "-//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();}
}