mybatis web使用02

处理 transfer 请求的 servlet

package com.wsd.web;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @description:
 * @author: Mr.Wang
 * @create: 2023-07-02 00:52
 **/
@WebServlet("transfer")
public class AccountServlet extends HttpServlet {

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取页面表单数据
        String fromActno = req.getParameter("fromActno");
        String toActno = req.getParameter("toActno");
        Double money = Double.parseDouble( req.getParameter("money") ) ;
        //调用service


    }
}

AccountService interface:

package com.wsd.service;

public interface AccountService {

    
    void transfer(String fromActno, String toActno, double money);
}

dao interface

package com.wsd.dao;

import com.wsd.pojo.Account;

/**
 * @author: Mr.Wang
 * @create: 2023-07-02 01:30
 **/
public interface AccountDao {

    /**
     * 根据账号获取账户信息
     * @param actno 账号
     * @return 账户信息
     */
    Account selectByActno(String actno);

    /**
     * 更新账户信息
     * @param act 账户信息
     * @return 1表示更新成功，其他值表示失败
     */
    int update(Account act);
}

实现类：

package com.wsd.dao.impl;

import com.wsd.dao.AccountDao;
import com.wsd.pojo.Account;
import com.wsd.util.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;

/**
 * @author: Mr.Wang
 * @create: 2023-07-02 01:36
 **/
public class AccountDaoImpl implements AccountDao {


    @Override
    public Account selectByActno(String actno) {
        //Get a SqlSession instance
        SqlSession sqlSession = SqlSessionUtil.openSession();
        //执行 selectByActno
        Account act = (Account)sqlSession.selectOne("selectByActno", actno);
        sqlSession.close();
        return act;
    }

    @Override
    public int update(Account act) {
        //Get a SqlSession instance
        SqlSession sqlSession = SqlSessionUtil.openSession();
        //执行 update
        int count = sqlSession.update("update", act);
        sqlSession.commit();
        sqlSession.close();
        return count;
    }
}

AccountMapper.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="account">
    <select id="selectByActno" resultType="com.wsd.pojo.Account">
        select * from t_act where actno = #{actno}
    </select>
    <update id="update">
        update t_act set balance = #{balance} where actno = #{actno}
    </update>
</mapper>

定义 MoneyNotEnoughExcecption

转账操作时，余额不足的情况下使用

package com.wsd.exception;

/**
 * @author: Mr.Wang
 * @create: 2023-07-02 09:06
 **/
public class MoneyNotEnoughExcecption extends Exception{
    public MoneyNotEnoughExcecption() {
    }

    public MoneyNotEnoughExcecption(String message) {
        super(message);
    }
}

修改接口，抛出异常

package com.wsd.service;

public interface AccountService {


    void transfer(String fromActno, String toActno, double money) throws Exception;
}

操作数据库失败时使用的异常

package com.wsd.exception;

/**
 * @author: Mr.Wang
 * @create: 2023-07-02 11:57
 **/
public class AppException extends Exception {

    public AppException() {
    }

    public AppException(String message) {
        super(message);
    }
}

service 实现类

package com.wsd.service.impl;

import com.wsd.dao.AccountDao;
import com.wsd.dao.impl.AccountDaoImpl;
import com.wsd.exception.AppException;
import com.wsd.exception.MoneyNotEnoughException;
import com.wsd.pojo.Account;
import com.wsd.service.AccountService;

/**
 * @author: Mr.Wang
 * @create: 2023-07-02 01:19
 **/
public class AccountServiceImpl implements AccountService {

    private AccountDao accountDao = new AccountDaoImpl();

    @Override
    public void transfer(String fromActno, String toActno, double money) throws MoneyNotEnoughException,AppException{
        // 查询转出账户的余额
        Account fromAct = accountDao.selectByActno(fromActno);
        //余额不足，抛出异常
        if (fromAct.getBalance() < money) {
            throw new MoneyNotEnoughException("对不起，您的余额不足。");
        }

        // 程序如果执行到这里说明余额充足
        // 修改账户余额
        Account toAct = accountDao.selectByActno(toActno);
        fromAct.setBalance(fromAct.getBalance() - money);
        toAct.setBalance(toAct.getBalance() + money);
        // 更新数据库
        int count = accountDao.update(fromAct);
        count += accountDao.update(toAct);
        if (count != 2) {
            throw new AppException("转账失败，未知原因！");
        }
    }
}

修改接口抛出的异常：

package com.wsd.service;

import com.wsd.exception.AppException;
import com.wsd.exception.MoneyNotEnoughException;

public interface AccountService {


    void transfer(String fromActno, String toActno, double money) throws MoneyNotEnoughException, AppException;
}

继续实现servlet：

package com.wsd.web;

import com.wsd.exception.AppException;
import com.wsd.exception.MoneyNotEnoughException;
import com.wsd.service.AccountService;
import com.wsd.service.impl.AccountServiceImpl;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * @description:
 * @author: Mr.Wang
 * @create: 2023-07-02 00:52
 **/
@WebServlet("/transfer")
public class AccountServlet extends HttpServlet {

    private AccountService accountService = new AccountServiceImpl();

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //获取页面表单数据
        String fromActno = req.getParameter("fromActno");
        String toActno = req.getParameter("toActno");
        Double money = Double.parseDouble( req.getParameter("money") ) ;
        //调用service
        try {
            accountService.transfer(fromActno,toActno,money);
            //Show the result after transfer success
            resp.sendRedirect(req.getContextPath()  + "/success.html");
        } catch (MoneyNotEnoughException e) {
            resp.sendRedirect(req.getContextPath()  + "/error1.html");
        } catch (AppException e) {
            resp.sendRedirect(req.getContextPath() + "/error2.html");
        }

    }
}

error1.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>transfer result</title>
</head>
<body>
<h1>The transfer failed because of insufficient balance</h1>
</body>
</html>

error2.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>transfer result</title>
</head>
<body>
<h1>The transfer failed, error occurred</h1>
</body>
</html>

success.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>transfer result</title>
</head>
<body>
<h1>The transfer success</h1>
</body>
</html>

运行：

tomcat 乱码

tomcat的/conf/logging.properties

Restart server

或则修改idea 控制台的编码方式为 utf-8,使与tomcat log 使用的编码方式保持一致

在IDEA里修改idea64.exe.vmoptions

菜单Help -> Edit Custom VM Options，在末尾增加如下代码，重启 idea

-Dfile.encoding=UTF-8

test:

模拟异常

package com.wsd.service.impl;

import com.wsd.dao.AccountDao;
import com.wsd.dao.impl.AccountDaoImpl;
import com.wsd.exception.AppException;
import com.wsd.exception.MoneyNotEnoughException;
import com.wsd.pojo.Account;
import com.wsd.service.AccountService;

/**
 * @author: Mr.Wang
 * @create: 2023-07-02 01:19
 **/
public class AccountServiceImpl implements AccountService {

    private AccountDao accountDao = new AccountDaoImpl();

    @Override
    public void transfer(String fromActno, String toActno, double money) throws MoneyNotEnoughException,AppException{
        // 查询转出账户的余额
        Account fromAct = accountDao.selectByActno(fromActno);
        //余额不足，抛出异常
        if (fromAct.getBalance() < money) {
            throw new MoneyNotEnoughException("对不起，您的余额不足。");
        }

        // 程序如果执行到这里说明余额充足
        // 修改账户余额
        Account toAct = accountDao.selectByActno(toActno);
        fromAct.setBalance(fromAct.getBalance() - money);
        toAct.setBalance(toAct.getBalance() + money);
        // 更新数据库
        int count = accountDao.update(fromAct);
        
        //模拟异常
        String s = null;
        s.toString();
        
        count += accountDao.update(toAct);
        if (count != 2) {
            throw new AppException("转账失败，未知原因！");
        }
    }
}

retest :

before test

出现异常

after test:

数据不一致

reason：

public void transfer(String fromActno, String toActno, double money) throws MoneyNotEnoughException,AppException{
        // 查询转出账户的余额
        Account fromAct = accountDao.selectByActno(fromActno);
        //余额不足，抛出异常
        if (fromAct.getBalance() < money) {
            throw new MoneyNotEnoughException("对不起，您的余额不足。");
        }

        // 程序如果执行到这里说明余额充足
        // 修改账户余额
        Account toAct = accountDao.selectByActno(toActno);
        fromAct.setBalance(fromAct.getBalance() - money);
        toAct.setBalance(toAct.getBalance() + money);
        // 更新数据库
        int count = accountDao.update(fromAct);

        //模拟异常
        String s = null;
        s.toString();

        count += accountDao.update(toAct);
        if (count != 2) {
            throw new AppException("转账失败，未知原因！");
        }
    }

1.更新 table

2.模拟异常

3.更新table

2 出现异常后，3没有执行

1.3 没有形成一个事务