Hibernate映射自定义数据类型

Hibernate映射自定义数据类型

数据库中存在一个email字段，并允许其中存储多个email地址，各地址之间使用 ; 分割，但是在POJO中，为了便于处理，email定义为一个List对象。
如何将String字段映射为List类型，Hibernate并没有提供原生支持，需要我们实现自己的UserType。
1.数据库定义

DROP   TABLE  t_user_mail;

CREATE   TABLE  t_user_mail (
       id  INT   NOT   NULL  AUTO_INCREMENT
     , name  VARCHAR ( 50 )
     , age  INT
     , email  VARCHAR ( 300 )
     ,  PRIMARY   KEY  (id)
);

2.
实现了UserType的自定义数据类型类EMailList

package  cn.blogjava.usertype;

import  java.io.Serializable;
import  java.sql.PreparedStatement;
import  java.sql.ResultSet;
import  java.sql.SQLException;
import  java.sql.Types;
import  java.util.ArrayList;
import  java.util.List;

import  org.apache.commons.lang.StringUtils;
import  org.hibernate.Hibernate;
import  org.hibernate.HibernateException;
import  org.hibernate.usertype.UserType;

public   class  EMailList  implements  UserType {

     private   static   final   char  SPLITTER =   ' ; ' ;
     private   static   final   int [] TYPES  =   new   int [] {Types.VARCHAR};
    
     public   int [] sqlTypes() {
         //  TODO Auto-generated method stub
         return  TYPES;
    }

     public  Class returnedClass() {
         //  TODO Auto-generated method stub
         return  List. class ;
    }

     public   boolean  equals(Object x, Object y)  throws  HibernateException {
         if (x  ==  y)  return   true ;
         if (x  !=   null   &  y  !=   null ) {
            List xlist  =  (List)x;
            List ylist  =  (List)y;
            
             if (xlist.size()  !=  ylist.size())  return   false ;
             for  ( int  i  =   0 ; i  <  xlist.size(); i ++ ) {
                String str1  =  (String)xlist.get(i);
                String str2  =  (String)ylist.get(i);
                 if ( ! str1.equals(str2))  return   false ;
            }
             return   true ;
        }
         return   false ;
    }

     public   int  hashCode(Object arg0)  throws  HibernateException {
         //  TODO Auto-generated method stub
         return   0 ;
    }

     public  Object nullSafeGet(ResultSet rs, String[] names, Object owner)
             throws  HibernateException, SQLException {
        String value  =  (String)Hibernate.STRING.nullSafeGet(rs, names[ 0 ]);
         if (value  !=   null ) {
             return  parse(value);
        }  else  {
             return   null ;
        }
    }

     public   void  nullSafeSet(PreparedStatement st, Object value,  int  index)
             throws  HibernateException, SQLException {
         if (value  !=   null ) {
            String str  =  assemble((List)value);
            Hibernate.STRING.nullSafeSet(st, str, index);
        }  else  {
            Hibernate.STRING.nullSafeSet(st, value, index);
        }
    }

     public  Object deepCopy(Object value)  throws  HibernateException {
        List sourceList  =  (List)value;
        List targetList  =   new  ArrayList();
        targetList.addAll(sourceList);
         return  targetList;
    }

     public   boolean  isMutable() {
         //  TODO Auto-generated method stub
         return   false ;
    }

     public  Serializable disassemble(Object arg0)  throws  HibernateException {
         //  TODO Auto-generated method stub
         return   null ;
    }

     public  Object assemble(Serializable arg0, Object arg1)
             throws  HibernateException {
         //  TODO Auto-generated method stub
         return   null ;
    }

     public  Object replace(Object arg0, Object arg1, Object arg2)
             throws  HibernateException {
         //  TODO Auto-generated method stub
         return   null ;
    }
    
     private  String assemble(List emailList) {
        StringBuffer strBuf  =   new  StringBuffer();
         for  ( int  i  =   0 ; i  <  emailList.size() - 1 ; i ++ ) {
            strBuf.append((String)emailList.get(i)).append(SPLITTER);            
        }
        strBuf.append(emailList.get(emailList.size() - 1 ));
         return  strBuf.toString();
    }
    
     private  List parse(String value) {
        String[] strs  =  StringUtils.split(value, SPLITTER);
        List emailList  =   new  ArrayList();
         for  ( int  i  =   0 ; i  <  strs.length; i ++ ) {
            emailList.add(strs[i]);
        }
         return  emailList;
    }

}

3.
配置文件TUserMail.hbm.xml

<?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>
<!-- 
        Auto-generated mapping file from
        the hibernate.org cfg2hbm engine
-->
    <class name = " cn.blogjava.usertype.TUserMail "  table = " t_user_mail "  catalog = " sample " >
        <id name = " id "  type = " integer " >
            <column name = " id "  />
            <generator class = " native "  />
        </id>
        <property name = " name "  type = " string " >
            <column name = " name "  length = " 50 "  />
        </property>
        <property name = " age "  type = " integer " >
            <column name = " age "  />
        </property>
        <property name = " email "  type = " cn.blogjava.usertype.EMailList " >
            <column name = " email "  length = " 300 "  />
        </property>
    </class>
</hibernate-mapping>

4.
在hibernate.cfg.xml载入TUserMail.hbm.xml

<?xml version = " 1.0 "  encoding = " UTF-8 " ?>
<!DOCTYPE hibernate-configuration PUBLIC
         " -//Hibernate/Hibernate Configuration DTD 3.0//EN "
         " http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd " >
<hibernate-configuration>
    <session-factory>
        <property name = " hibernate.connection.driver_class " >com.mysql.jdbc.Driver</property>
        <property name = " hibernate.connection.password " > 1234 </property>
        <property name = " hibernate.connection.url " >jdbc:mysql://localhost: 3306 /sample</property>
        <property name = " hibernate.connection.username " >root</property>
        <property name = " hibernate.dialect " >org.hibernate.dialect.MySQLDialect</property>
        <mapping resource = " cn/blogjava/start/TUser.hbm.xml "  />
        <mapping resource = " cn/blogjava/usertype/TUserMail.hbm.xml "  />
    </session-factory>
</hibernate-configuration>

5.
测试类HibernateTest.java

package  cn.blogjava.usertype;

import  java.util.ArrayList;
import  java.util.List;

import  junit.framework.Assert;
import  junit.framework.TestCase;

import  org.hibernate.HibernateException;
import  org.hibernate.Session;
import  org.hibernate.SessionFactory;
import  org.hibernate.Transaction;
import  org.hibernate.cfg.Configuration;


public   class  HibernateTest  extends  TestCase {
    
    Session session  =   null ;
     /**
     * JUnit中的setUp方法在TestCase初始化的时候会自动调用
     * 一般用于初始化公用资源
      */
     protected   void  setUp() {
         try  {
             /**
             * 可以采用hibernate.properties或者hibernate.cfg.xml
             * 配置文件的初始化代码
             * 
             * 采用hibernate.properties
             * Configuration config = new Configuration()；
             * config.addClass(TUser.class);
              */
            
             // 采用hibernate.cfg.xml配置文件，与上面的方法对比，两个差异
             // 1.Configuration的初始化方式
             // 2.xml
            Configuration config  =   new  Configuration().configure();
            SessionFactory sessionFactory  =  config.buildSessionFactory();
            session  =  sessionFactory.openSession();
            
        }  catch  (HibernateException e) {
             //  TODO: handle exception
            e.printStackTrace();
        }        
    }

     /**
     * JUnit中的tearDown方法在TestCase执行完毕的时候会自动调用
     * 一般用于释放资源
      */     
     protected   void  tearDown() {
         try  {
            session.close();        
        }  catch  (HibernateException e) {
             //  TODO: handle exception
            e.printStackTrace();
        }        
    }    
    
     /**
     * 对象持久化测试(Insert方法)
      */         
     public   void  testInsert() {
        Transaction tran  =   null ;
         try  {
            tran  =  session.beginTransaction();
            TUserMail user  =   new  TUserMail();
            user.setName( " byf " );
            List list  =   new  ArrayList();
            list.add( " [email protected] " );
            list.add( " [email protected] " );
            user.setEmail(list);
            session.save(user);
            session.flush();
            tran.commit();
            Assert.assertEquals(user.getId().intValue() > 0  , true );
        }  catch  (HibernateException e) {
             //  TODO: handle exception
            e.printStackTrace();
            Assert.fail(e.getMessage());
             if (tran  !=   null ) {
                 try  {
                    tran.rollback();
                }  catch  (Exception e1) {
                     //  TODO: handle exception
                    e1.printStackTrace();
                }
            }
        }
    }
    
     /**
     * 对象读取测试(Select方法)
      */             
     public   void  testSelect(){
        String hql  =   "  from TUserMail where name='byf' " ;
         try  {
            List userList  =  session.createQuery(hql).list();
            TUserMail user  =  (TUserMail)userList.get( 0 );
            List mailList  =  user.getEmail();

            Assert.assertEquals((String)mailList.get( 0 ),  " [email protected] " );
            Assert.assertEquals((String)mailList.get( 1 ),  " [email protected] " );
        }  catch  (Exception e) {
             //  TODO: handle exception
            e.printStackTrace();
            Assert.fail(e.getMessage());
        }
    }
}

运行测试代码，观察数据库中，可以发现email地址信息已经以";"分隔的形式保存。同时，在数据读取时，我们也无需面对原始的";"分隔字符串，转而只需要处理List类型数据即可。