MySQL数据库事务实例（模拟银行转账）

在数据库系列文章中[MySQL数据库事务基本操作](http://blog.csdn.net/fengpojian/article/details/73571983)
介绍了MySQL数据库基本的事务操作。这篇文章将介绍一个实例来更好的理解学习MySQL数据库事务。
这个Demo主要是模拟银行转账的过程，两个账户发生转账关系时，首先改变双方账户的余额状态。
随后验证转出方账户是否有足够的余额来支撑此次的转账操作，若余额不足，则抛出“账户余额不足”异常。
请注意，这个Demo只适用于单线程的情况。

java
/**
* 单线程下的数据库事务
* 模拟银行转账
* @author LinGer
*
*/
public class Transaction
{
public boolean transfrom(int fromId, int toId, double amount)
{
Connection con = MyUtil.getCon();
String sql1 = "update tb_account set balance = balance - ? where userId = ?;";
String sql2 = "update tb_account set balance = balance + ? where userId = ?;";
String sql3 = "select balance  from tb_account where userId = ?;";
PreparedStatement ps1 = null;
PreparedStatement ps2 = null;
PreparedStatement ps3 = null;
ResultSet rs = null;
try
{
//开启事务
con.setAutoCommit(false);
//转账时涉及的两个账户以及各账户的金额变动
ps1 = con.prepareStatement(sql1);
ps1.setDouble(1, amount);
ps1.setInt(2, fromId);
ps1.executeUpdate();

ps2 = con.prepareStatement(sql2);
ps2.setDouble(1, amount);
ps2.setInt(2, toId);
ps2.executeUpdate();

//检查转出方账户的余额是否足够支持此次转账金额；如果余额不足，则抛出“余额不足”异常，并回滚
ps3 = con.prepareStatement(sql3);
ps3.setInt(1, fromId);
rs = ps3.executeQuery();
Dou
4000
ble balance = 0.0;
if(rs.next())
{
balance = rs.getDouble("balance");
}
if(balance < 0)
{
throw new Exception("账户余额不足");
}
con.commit();
return true;
} catch (Exception e)
{
e.printStackTrace();
}
try
{
con.rollback();
} catch (SQLException e)
{
e.printStackTrace();
}finally{
try
{
rs.close();
ps1.close();
ps2.close();
ps3.close();
con.close();
} catch (SQLException e)
{
e.printStackTrace();
}
}
return false;
}
}

java
/**
* 工具类 获得Connection连接
* @return
*/
public static Connection getCon()
{
String DBDriver = "com.mysql.jdbc.Driver";
String DBUrl = "jdbc:mysql://localhost:3306/study?autoReconnect=true&"
+ "failOverReadOnly=false&useUnicode=true&characterEncoding=UTF-8";
String name = "root";
String pass = "123";
Connection con = null;
try {
Class.forName(DBDriver);
con = DriverManager.getConnection(DBUrl,name,pass);
} catch (Exception e) {
e.printStackTrace();
}

return con;
}

java
/**
* 实体类 模拟银行账户
* @author LinGer
*
*/
public class User
{
private int userId;
private String userName;
private Double balance; //账户余额

//get && set
public int getUserId()
{
return userId;
}
public void setUserId(int userId)
{
this.userId = userId;
}
public String getUserName()
{
return userName;
}
public void setUserName(String userName)
{
this.userName = userName;
}
public Double getBalance()
{
return balance;
}
public void setBalance(Double balance)
{
this.balance = balance;
}
}

这篇博客的代码参考了https://www.oschina.net/code/snippet_2271303_44733#62843
非常感谢博主。