垃圾版代码，只提供一个思路
第一个版本
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP ‘index.jsp‘ starting page</title>
</head>
<body>
<form action="${pageContext.request.contextPath}/account" method="post">
转款人<input type="text" name="outuser"> 收款人<input type="text"
name="inuser"> 金额<input type="text" name="money"> <input
type="submit" value="转账">
</form>
</body>
</html>
servlet
public class AccountServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
// 1.收集数据
String outuser = request.getParameter("outuser");
String inuser = request.getParameter("inuser");
String money = request.getParameter("money");
// 2.调用AccountService中的account方法
AccountService service = new AccountService();
try {
service.account(outuser, inuser, money);
response.getWriter().write("汇款成功");
} catch (AccountException e) {
e.printStackTrace();
response.getWriter().write(e.getMessage());
}
}
}
service
public class AccountService {
// 原始转账方法
public void _account(String outuser, String inuser, String money)
throws AccountException {
AccountDao dao = new AccountDao();
// 获取连接对象，并开启事务
Connection con = null;
try {
con = JdbcUtils.getConnection();
con.setAutoCommit(false); // 开启事务
// 调用AccountDao中两个方法
// 转出
dao.accountOut(con, outuser, money);
// 转入
dao.accountIn(con, inuser, money);
} catch (SQLException e) {
e.printStackTrace();
// 事务回滚
try {
con.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
throw new AccountException("转账失败");
} catch (AccountException e) {
e.printStackTrace();
// 事务回滚
try {
con.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
throw e;
} finally {
try {
con.commit(); // 提交事务
con.close(); // 关闭资源
} catch (SQLException e) {
e.printStackTrace();
}
}
}
// 转账方法
public void account(String outuser, String inuser, String money)
throws AccountException {
AccountDao dao = new AccountDao();
try {
// 开启事务
JdbcUtils.startTransaction();
// 转出
dao.accountOut(outuser, money);
// 转入
dao.accountIn(inuser, money);
} catch (SQLException e) {
e.printStackTrace();
// 事务回滚
try {
JdbcUtils.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
throw new AccountException("转账失败");
} catch (AccountException e) {
e.printStackTrace();
// 事务回滚
try {
JdbcUtils.rollback();
} catch (SQLException e1) {
e1.printStackTrace();
}
throw e;
} finally {
try {
JdbcUtils.commit();// 提交事务
JdbcUtils.closeConnection(); // 关闭资源
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
dao
public class AccountDao {
// 转入
public void accountIn(Connection con, String inuser, String money)
throws SQLException, AccountException {
String sql = "update account set money=money+? where username=?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setString(1, money);
pst.setString(2, inuser);
int row = pst.executeUpdate();
if (row == 0) {
throw new AccountException("转入失败");
}
pst.close();
}
// 转出
public void accountOut(Connection con, String outuser, String money)
throws SQLException, AccountException {
String sql = "update account set money=money-? where username=?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setString(1, money);
pst.setString(2, outuser);
int row = pst.executeUpdate();
if (row == 0) {
throw new AccountException("转出失败");
}
pst.close();
}
// 转入--使用ThreadLocal获取连接
public void accountIn(String inuser, String money) throws SQLException,
AccountException {
Connection con = JdbcUtils.getConnection();
String sql = "update account set money=money+? where username=?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setString(1, money);
pst.setString(2, inuser);
int row = pst.executeUpdate();
if (row == 0) {
throw new AccountException("转入失败");
}
pst.close();
}
// 转出
public void accountOut(String outuser, String money) throws SQLException,
AccountException {
Connection con = JdbcUtils.getConnection();
String sql = "update account set money=money-? where username=?";
PreparedStatement pst = con.prepareStatement(sql);
pst.setString(1, money);
pst.setString(2, outuser);
int row = pst.executeUpdate();
if (row == 0) {
throw new AccountException("转出失败");
}
pst.close();
}
}
exception
public class AccountException extends Exception {
public AccountException() {
super();
}
public AccountException(String message, Throwable cause) {
super(message, cause);
}
public AccountException(String message) {
super(message);
}
public AccountException(Throwable cause) {
super(cause);
}
}
//高级的，使用ThreadLocal
public class JdbcUtils {
private static final String DRIVERCLASSNAME;
private static final String URL;
private static final String USER;
private static final String PASSWORD;
static {
ResourceBundle bundle = ResourceBundle.getBundle("jdbc");
DRIVERCLASSNAME = bundle.getString("DRIVERCLASSNAME");
URL = bundle.getString("URL");
USER = bundle.getString("USER");
PASSWORD = bundle.getString("PASSWORD");
}
static {
try {
Class.forName(DRIVERCLASSNAME);
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
private static final ThreadLocal<Connection> tl = new ThreadLocal<Connection>(); // 它就相当于是一个Map集合。
public static Connection getConnection() throws SQLException {
// Connection con = tl.get(); // 从ThreadLocal中获取，第一次一得到的一定是null.
// if (con == null) {
Connection con = DriverManager.getConnection(URL, USER, PASSWORD);
// tl.set(con);// 将con装入到ThreadLocal中。
// }
return con;
}
// 封装事务操作.
// 开启事务
public static void startTransaction() throws SQLException {
Connection con = getConnection();
con.setAutoCommit(false);
}
public static void rollback() throws SQLException {
Connection con = getConnection();
con.rollback();
}
// 事务提交
public static void commit() throws SQLException {
Connection con = getConnection();
con.commit();
}
public static void closeStatement(Statement st) throws SQLException {
if (st != null)
st.close();
}
public static void closeResultSet(ResultSet rs) throws SQLException {
if (rs != null)
rs.close();
}
ThreadLocal
它的底层是使用了一个Map集合
Map<Thread,Object>
它的key就是当前的线程对象.
set(Object obj) 它就相当于 map.put(Thread.currentThread(),obj);
get()它就相当于 map.get(Thread.currentThread()));
时间： 2024-10-25 23:24:24