缺点：Dao层面把Service层面的操作完成了，不利于后期的代码修改和重构

1.自行创建C3P0Util

account数据库

 

2.jar包

3.Dao层面

接口：

package com.learning.dao;import com.learning.domain.Account;public interface AccountDao {    /**     * 转账     * @param fromname 转出用户     * @param toname  转入用户     * @param money  转账金额     */    public void updateAccount(String fromname,String toname,double money)throws Exception;}

 实现类：

package com.learning.dao.impl;import java.sql.SQLException;import org.apache.commons.dbutils.QueryRunner;import com.learning.dao.AccountDao;import com.learning.util.C3P0Util;public class AccountDaoImpl implements AccountDao {    public void updateAccount(String fromname, String toname, double money) throws Exception {        //创建一个QueryRunner对象        QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());        qr.update("update account set money=money-? where name=?",money,fromname);        qr.update("update account set money=money+? where name=?",money,toname);    }}