mybatis学习笔记之在WEB中应用MyBatis
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
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
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 {
@Override
public Account selectByActno(String actno) {
SqlSession sqlSession = SqlSessionUtil.openSession();
Account account = (Account) sqlSession.selectOne("account.selectByActno", actno);
sqlSession.close();
return account;
}
@Override
public 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();
@Override
public 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();
@Override
protected 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();
@Override
protected 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();
}
}
写好的工具类，方便在dao层获取sqlsession对象。
银行转账小功能