控制層
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");

        String from = request.getParameter("from");
        String to 
 
= request.getParameter("to");
        double money =Double.parseDouble( request.getParameter("money"));
        MoneyService ms = new MoneyService();
        Boolean flag = ms.trans(from,to,money);
        if(flag) {
            response.getWriter().println("轉賬成功");
        }else {
            response.getWriter().println(
 
"轉賬失敗");
        }
    }
業務層
    public Boolean trans(String from, String to, double money) {
            MoneyDao md = new MoneyDao();
            Connection conn = c3p0Util.getConn();
        try {
                conn.setAutoCommit(false);
                int a = md.from(from,money,conn);
                
 
int b = md.to(to,money,conn);
                if(a*b>0) {
                    DbUtils.commitAndCloseQuietly(conn);
                    return true;
                }    
        } catch (Exception e) {                
            e.printStackTrace();
            DbUtils.rollbackAndCloseQuietly(conn);
        }        
        return false;
    }
持久層
public class MoneyDao {

    public int from(String from, double money,Connection conn) throws Exception {

        String sql = "update account set money=money-? where name=?";
        QueryRunner qr = new QueryRunner();
        int i = qr.update(conn, sql, money,from);
        return i;    
    }

    public int to(String to, double money,Connection conn) throws Exception {

        String sql = "update account set money=money+? where name=?";
        QueryRunner qr = new QueryRunner();
        int i = qr.update(conn, sql, money,to);
        return i;
    }
}