Hibernate逍遥游记-第13章 映射实体关联关系-003单向多对多

0.

1.

 drop database if exists SAMPLEDB;
 create database SAMPLEDB;
 use SAMPLEDB;

 create table MONKEYS(
    ID bigint not null,
    NAME varchar(15),
    primary key (ID)
 );

 create table TEACHERS(
   ID bigint not null,
   NAME varchar(15),
   primary key(ID)
 );

 create table LEARNING(
   MONKEY_ID bigint not null,
   TEACHER_ID bigint not null,
   primary key(MONKEY_ID,TEACHER_ID)
 );

 alter table LEARNING add index IDX_MONKEY(MONKEY_ID),
 add constraint FK_MONKEY foreign key (MONKEY_ID) references MONKEYS(ID);

 alter table LEARNING add index IDX_TEACHER(TEACHER_ID),
 add constraint FK_TEACHER foreign key (TEACHER_ID) references TEACHERS(ID);

2.

 <?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="mypack.Monkey" table="MONKEYS" >
     <id name="id" type="long" column="ID">
       <generator class="increment"/>
     </id>

     <property name="name" column="NAME" type="string" />

     <set name="teachers" table="LEARNING"
         lazy="true"
         cascade="save-update">
         <key column="MONKEY_ID" />
         <many-to-many class="mypack.Teacher" column="TEACHER_ID" />
     </set>

   </class>

 </hibernate-mapping>

3.

 <?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="mypack.Teacher" table="TEACHERS" >
     <id name="id" type="long" column="ID">
       <generator class="increment"/>
     </id>

     <property name="name" column="NAME" type="string" />

   </class>
 </hibernate-mapping>

4.

 package mypack;
 import java.util.Set;
 import java.util.HashSet;

 public class Monkey {

     private Long id;
     private String name;
     private Set teachers=new HashSet();

     public Monkey(String name, Set teachers) {
         this.name = name;
         this.teachers = teachers;

     }

     /** default constructor */
     public Monkey() {
     }

     public Long getId() {
         return this.id;
     }

     public void setId(Long id) {
         this.id = id;
     }

     public String getName() {
         return this.name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public Set getTeachers() {
         return this.teachers;
     }

     public void setTeachers(Set teachers) {
         this.teachers = teachers;
     }

  }

5.

 package mypack;
 public class Teacher{
     private Long id;
     private String name;

     /** full constructor */
     public Teacher(String name ) {
         this.name = name;
     }

     /** default constructor */
     public Teacher() {
     }

     public String getName() {
         return this.name;
     }

     public void setName(String name) {
         this.name = name;
     }

     public Long getId() {
         return this.id;
     }

     public void setId(Long id) {
         this.id = id;
     }

 }

6.

 package mypack;

 import org.hibernate.*;
 import org.hibernate.cfg.Configuration;
 import java.util.*;

 public class BusinessService{
   public static SessionFactory sessionFactory;
   static{
      try{
        Configuration config = new Configuration().configure();
        sessionFactory = config.buildSessionFactory();
     }catch(RuntimeException e){e.printStackTrace();throw e;}
   }

   public void saveMonkey(Monkey monkey){
     Session session = sessionFactory.openSession();
     Transaction tx = null;
     try {
       tx = session.beginTransaction();
       session.save(monkey);
       tx.commit();

     }catch (RuntimeException e) {
       if (tx != null) {
         tx.rollback();
       }
       throw e;
     } finally {
       session.close();
     }
   }

  public Monkey loadMonkey(Long id){
     Session session = sessionFactory.openSession();
     Transaction tx = null;
     try {
       tx = session.beginTransaction();
       Monkey monkey=(Monkey)session.get(Monkey.class,id);
       Hibernate.initialize(monkey.getTeachers());
       tx.commit();

       return monkey;

     }catch (RuntimeException e) {
       if (tx != null) {
         tx.rollback();
       }
       throw e;
     } finally {
       session.close();
     }
   }

   public void printMonkey(Monkey monkey){
     Set teachers=monkey.getTeachers();
     Iterator it=teachers.iterator();
     while(it.hasNext()){
       Teacher teacher=(Teacher)it.next();
       System.out.println(monkey.getName()+" "+teacher.getName());
     }

   }

  public void test(){

       Teacher teacher1=new Teacher("¶þÀÉÉñ");
       Teacher teacher2=new Teacher("ºìº¢¶ù");

       Monkey monkey1=new Monkey();
       monkey1.setName("ÖǶàÐÇ");
       monkey1.getTeachers().add(teacher1);
       monkey1.getTeachers().add(teacher2);

       Monkey monkey2=new Monkey();
       monkey2.setName("ÀÏÍçͯ");
       monkey2.getTeachers().add(teacher1);

       saveMonkey(monkey1);
       saveMonkey(monkey2);

       monkey1=loadMonkey(monkey1.getId());
       printMonkey(monkey1);

   }

   public static void main(String args[]){
     new BusinessService().test();
     sessionFactory.close();
   }
 }

7.