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;

CREATE   TABLE  t_user (
       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 tuser;

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.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};
	
	@Override
	public int[] sqlTypes() {
		return TYPES;
	}

	@Override
	public Class returnedClass() {
		return List.class;
	}

	@Override
	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 index = 0; index < xList.size(); index++){
				String str1 = (String) xList.get(index);
				String str2 = (String) yList.get(index);
				if(str1 != str2){
					return false;
				}
			}
			
			return true;
		}
		
		return false;
	}

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

	@Override
	public void nullSafeSet(PreparedStatement st, Object value, int index)
			throws HibernateException, SQLException {
		System.out.println("Set method executed");
		if(value != null){
			String str = assemble((List)value);
			Hibernate.STRING.nullSafeSet(st, str, index);
		}else{
			Hibernate.STRING.nullSafeSet(st, null, index);
		}
	}

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

	@Override
	public boolean isMutable() {
		return false;
	}

	/**
	 * 将String拼装为一个字符串，以“；”分隔
	 * @param emailList
	 * @return
	 */
	private String assemble(List emailList){
		StringBuffer strBuf = new StringBuffer();
		for(int i = 0; i < emailList.size() - 1; i++){
			strBuf.append(emailList.get(i)).append(SPLITTER);
		}
		strBuf.append(emailList.get(emailList.size() - 1));
		
		return strBuf.toString();
	}
	
	/**
	 * 将以“；”分隔的字符串解析为一个字符串数组
	 * @param value
	 * @return
	 */
	private List parse(String value){
		String[] strs = value.split(SPLITTER + "");
		List emailList = new ArrayList();
		for(int i = 0; i < strs.length; i++){
			emailList.add(strs[i]);
		}
		
		return emailList;
	}

	@Override
	public Object assemble(Serializable arg0, Object arg1)
			throws HibernateException {
		return null;
	}

	@Override
	public Serializable disassemble(Object arg0) throws HibernateException {
		return null;
	}

	@Override
	public int hashCode(Object arg0) throws HibernateException {
		return 0;
	}

	@Override
	public Object replace(Object arg0, Object arg1, Object arg2)
			throws HibernateException {
		return null;
	}
}

3.配置文件TUser.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>
	<class name="tuser.TUser" table="T_USER">
		<id name="id" type="java.lang.Integer">
			<column name="ID"/>
			<generator class="native"></generator>
		</id>
		<property name="name" type="java.lang.String">
			<column name="NAME"/>
		</property>
		<property name="age" type="java.lang.String">
			<column name="AGE"/>
		</property>
		<property name="email" type="tuser.EmailList">
			<column name="EMAIL"/>
		</property>

	</class>
</hibernate-mapping>

4.在hibernate.cfg.xml载入TUser.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="connection.driver_class">
			com.mysql.jdbc.Driver
		</property>
		<property name="connection.url">
			jdbc:mysql://localhost:3306/hibernate
		</property>
		<property name="connection.username">
			root
		</property>
		<property name="connection.password">
			system
		</property>
		<property name="dialect">
			org.hibernate.dialect.MySQLDialect
		</property>
		<property name="javax.persistence.validation.mode">
			none
		</property>
		
		
		<property name="c3p0.min_size">5</property>
		<property name="c3p0.max_size">20</property>
		<property name="c3p0.timeout">300</property>
		<property name="c3p0.max_statements">50</property>
		<property name="c3p0.idle_test_period">3000</property>
		
		
		<property name="show_sql">false</property>
		<property name="format_sql">false</property>
		
		<mapping resource="hello/Message.hbm.xml"/>
		<mapping resource="user/User.hbm.xml"/>
		<mapping resource="tuser/TUser.hbm.xml"/>

	</session-factory>
</hibernate-configuration>

5.测试类HibernateTest.java

package test;

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

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;
import org.junit.After;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;

import tuser.TUser;
import user.User;

public class HibernateTest extends TestCase {
	Session session = null;
	
	@Before
	protected void setUp() throws Exception {
		try {
			Configuration configure = new Configuration().configure();
			SessionFactory sessionFactory = configure.buildSessionFactory();
			session = sessionFactory.openSession();
		} catch (HibernateException e) {
			e.printStackTrace();
		}
	}

	@After
	protected void tearDown() throws Exception {
		try {
			session.close();
		} catch (HibernateException e) {
			e.printStackTrace();
		}
	}
	
	@Test
	public void testTUser(){
		Transaction tran = null;
        try {
            tran = session.beginTransaction();
            TUser user = new TUser();
            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) {
            e.printStackTrace();
            Assert.fail(e.getMessage());
            if(tran != null) {
                try {
                    tran.rollback();
                } catch (Exception e1) {
                    e1.printStackTrace();
                }
            }
        }
	}
	
	/**
     * 对象读取测试(Select方法)
     */            
    public void testSelect(){
        String hql = " from TUser where name='byf'";
        try {
            List userList = session.createQuery(hql).list();
            TUser user = (TUser)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) {
            e.printStackTrace();
            Assert.fail(e.getMessage());
        }
    }
}

6.TUser类

package tuser;

import java.io.Serializable;
import java.util.List;

public class TUser implements Serializable {
	private static final long serialVersionUID = 1901560971512450430L;

	private Integer id;
	private String name;
	private Integer age;
	private List email;
	
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Integer getAge() {
		return age;
	}
	public void setAge(Integer age) {
		this.age = age;
	}
	public List getEmail() {
		return email;
	}
	public void setEmail(List email) {
		this.email = email;
	}
}

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。