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mybatis学习笔记之在WEB中应用MyBatis

news 2025/8/14 2:21:30

文章目录

数据库表的设计和准备数据
环境搭建
前端页面编写
后端代码实现
- 后端代码目录
- dao层
- service
- web
- pojo
- Utils

数据库表的设计和准备数据

在这里插入图片描述

环境搭建

在pom.xml中配置依赖（logback、mybatis、mysql、servlet）
注意引入tomcat

前端页面编写

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>银行账户转账</title>
</head>
<body><form action="/bank/transfer" method="post">转出账户：<input type="text" name="fromActno"><br>转入账号：<input type="text" name="toActno"><br>转账金额：<input type="text" name="money"><br><input type="submit" value="转账"></form>
</body>
</html>

后端代码实现

后端代码目录

在这里插入图片描述

dao层

//AccountDaoImpl
package com.example.bank.dao.impl;import com.example.bank.dao.AccountDao;
import com.example.bank.pojo.Account;
import com.example.bank.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;public class AccountDaoImpl implements AccountDao {@Overridepublic Account selectByActno(String actno) {SqlSession sqlSession = SqlSessionUtil.openSession();Account account = (Account) sqlSession.selectOne("account.selectByActno", actno);sqlSession.close();return account;}@Overridepublic int updateByActno(Account act) {SqlSession sqlSession = SqlSessionUtil.openSession();int count = sqlSession.update("account.updateByActno",act);sqlSession.commit();sqlSession.close();return count;}
}

package com.example.bank.dao;import com.example.bank.pojo.Account;//dao对象中的任何一个方法和业务不挂钩，没有任何业务逻辑在里面
//DAO中的方法就是做CRUD的
public interface AccountDao {//根据账号查询账户信息Account selectByActno(String actno);//更新账户信息int updateByActno(Account act);
}

dao层是三层架构的最底层，是数据访问层，主要是连接MySQL，并做数据的CRUD，不包含任何的逻辑

service

//AccountServiceImpl
package com.example.bank.service.impl;import com.example.bank.dao.AccountDao;
import com.example.bank.dao.impl.AccountDaoImpl;
import com.example.bank.exceptions.MoneyNotEnoughException;
import com.example.bank.exceptions.TransferException;
import com.example.bank.pojo.Account;
import com.example.bank.service.AccountService;public class AccountServiceImpl implements AccountService {private AccountDao accountDao = new AccountDaoImpl();@Overridepublic void transfer(String fromActno, String toActno, double money) throws MoneyNotEnoughException, TransferException {//1、判断转出账户的余额是否充足Account fromAct = accountDao.selectByActno(fromActno);if (fromAct.getBalance() < money){//2、如果转出账户余额不足，提示用户throw new MoneyNotEnoughException("对不起，您的余额不足");}//3、如果转出账户余额充足，更新转出账户余额（update）//先更新内存中java对象account的余额Account toAct = accountDao.selectByActno(toActno);fromAct.setBalance(fromAct.getBalance() - money);toAct.setBalance(toAct.getBalance() + money);int count = accountDao.updateByActno(fromAct);//4、更新转入账户余额（update）count += accountDao.updateByActno(toAct);if (count != 2){throw new TransferException("转账异常，未知原因");}}}

//AccountService
package com.example.bank.service;import com.example.bank.exceptions.MoneyNotEnoughException;
import com.example.bank.exceptions.TransferException;public interface AccountService {
//    @param fromActno 转出账号
//    @param toActno 转入账号
//    @param money 转账金额void transfer(String fromActno, String toActno, double money) throws MoneyNotEnoughException, TransferException;
}

service层是业务逻辑层，主要是对数据进行逻辑的处理，页面的改变等。这里的逻辑主要就是对余额先进行能否转移的判断，其次是对账户余额的转移改变，最后就是对不同错误的出现返回不同的错误类型

web

//AccountServlet
package com.example.bank.web;import com.example.bank.exceptions.MoneyNotEnoughException;
import com.example.bank.exceptions.TransferException;
import com.example.bank.service.AccountService;
import com.example.bank.service.impl.AccountServiceImpl;import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/transfer")
public class AccountServlet extends HttpServlet {//为了让这个对象在其他方法中也可以用private AccountService accountService = new AccountServiceImpl();@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response)throws IOException{//获取表单数据String fromActno = request.getParameter("fromActno");String toActno = request.getParameter("toActno");double money = Double.parseDouble(request.getParameter("money"));try {//调用servlet的转账方法完成转账。（调业务层）accountService.transfer(fromActno,toActno,money);//程序能够走到这里，表示转账一定成功了//调用view完成展示结果response.sendRedirect(request.getContextPath() + "/success.html");} catch (MoneyNotEnoughException e) {response.sendRedirect(request.getContextPath() + "/error1.html");} catch (TransferException e) {response.sendRedirect(request.getContextPath() + "/error2.html");}}
}

展示层，获取表单数据以及针对不同情况错误的出现展示不同的页面信息。

pojo

pojo是封装类，账号的类型里面有的相关数据，一方面能在java中进行数据操作，另一方面对接MySQL的账户信息，方便CRUD。

package com.example.bank.web;import com.example.bank.exceptions.MoneyNotEnoughException;
import com.example.bank.exceptions.TransferException;
import com.example.bank.service.AccountService;
import com.example.bank.service.impl.AccountServiceImpl;import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/transfer")
public class AccountServlet extends HttpServlet {//为了让这个对象在其他方法中也可以用private AccountService accountService = new AccountServiceImpl();@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response)throws IOException{//获取表单数据String fromActno = request.getParameter("fromActno");String toActno = request.getParameter("toActno");double money = Double.parseDouble(request.getParameter("money"));try {//调用servlet的转账方法完成转账。（调业务层）accountService.transfer(fromActno,toActno,money);//程序能够走到这里，表示转账一定成功了//调用view完成展示结果response.sendRedirect(request.getContextPath() + "/success.html");} catch (MoneyNotEnoughException e) {response.sendRedirect(request.getContextPath() + "/error1.html");} catch (TransferException e) {response.sendRedirect(request.getContextPath() + "/error2.html");}}
}

Utils

package com.example.bank.utils;import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;import java.io.IOException;public class SqlSessionUtil {private SqlSessionUtil(){}private static SqlSessionFactory sqlSessionFactory;static {try {sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));} catch (IOException e) {throw new RuntimeException(e);}}public static SqlSession openSession(){return sqlSessionFactory.openSession();}}