求一个Hibernate多对多自身关联的例子代码
求一个Hibernate多对多自身关联的例子代码
[解决办法]
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 setCourse 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();
}
}
