Hibernate学习（六）---【一对多双项】

Hibernate学习（六）---【一对多双项】

package  com.zzn.hibernate.oneToMany;

public   class  Student {
     private   int  id;
     private  String name;
     private  Classes classes;
    
     public  Classes getClasses() {
         return  classes;
    }
     public   void  setClasses(Classes classes) {
         this .classes  =  classes;
    }
     public   int  getId() {
         return  id;
    }
     public   void  setId( int  id) {
         this .id  =  id;
    }
     public  String getName() {
         return  name;
    }
     public   void  setName(String name) {
         this .name  =  name;
    }
}

package  com.zzn.hibernate.oneToMany;

import  java.util.Set;

public   class  Classes {
     private   int  id;
     private  String name;
     private  Set students;

     public  Set getStudents() {
         return  students;
    }
     public   void  setStudents(Set students) {
         this .students  =  students;
    }
     public   int  getId() {
         return  id;
    }
     public   void  setId( int  id) {
         this .id  =  id;
    }
     public  String getName() {
         return  name;
    }
     public   void  setName(String name) {
         this .name  =  name;
    }
    
    
}

<? 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.zzn.hibernate.oneToMany.Student "  table = " STUDENT " >
         < id name = " id "  column = " id " >
             < generator  class = " native "   />
         </ id >
         < property name = " name "   />
         <!--  一对多双向关联，在多的这一段必须有column，并且和一的一段中 < key /> 中的column = " classesid " 一样  -->
         < many - to - one name = " classes "  column = " classesid "  cascade = " all " />
     </ class >

</ hibernate - mapping >

<? 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  package ="com.zzn.hibernate.oneToMany" >
     < class  name ="Classes"  table ="CLASSES" >
         < id  name ="id"  column ="id" >
             < generator  class ="native"   />
         </ id >
         < property  name ="name"   />
         <!-- cascade="all"才能操作classes时级联操作student   -->
         < set  name ="students"  cascade ="all"  inverse ="true" >
             <!--  key 这里不能是not-null="true"  -->
             < key  column ="classesid" />
             < one-to-many  class ="Student" />
         </ set >
     </ class >
</ hibernate-mapping >

TEST

     public   void  OneToManySaveN() {
        Session session  =   null ;
        Transaction tx  =   null ;
         try  {
            session  =  HibernateUtils.getSession();
            tx  =  session.beginTransaction();
            
            Classes classes  =   new  Classes();
            classes.setName( " 俄罗斯 " );
            
            Student student  =   new  Student();
            student.setName( " 列宁 " );
            student.setClasses(classes);
            session.save(student);
            
        }  catch  (Exception e) {
            e.printStackTrace();
        }  finally  {
             if  (session  !=   null ) {
                 if  (session.isOpen()) {
                    tx.commit();
                    session.close();
                }
            }
        }
    }
    
     public   void  OneToManyLoadN() {
        Session session  =   null ;
        Transaction tx  =   null ;
         try  {
            session  =  HibernateUtils.getSession();
            tx  =  session.beginTransaction();
            
            Student    student  =  (Student)session.load(Student. class ,  6 );
            System.out.println(student.getName());
            System.out.println(student.getClasses().getName());
            
        }  catch  (Exception e) {
            e.printStackTrace();
        }  finally  {
             if  (session  !=   null ) {
                 if  (session.isOpen()) {
                    tx.commit();
                    session.close();
                }
            }
        }
    }