Word count: 6.2k   |   Reading time≈ 35 min

title: java课程大作业 银行操作系统

使用javaweb 实现前端和数据库的交互

前端资源

我自己写的前端资源是十分简单的 简约的 以HTML为主 简单的css 并没有JavaScript。使用的是.jsp

来实现前后端交互

登录界面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 8:59
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>login</title>
    <style type="text/css">
        h1{align-content: center;text-align: center;}
        body{background-color:wheat}
        #login{

            width: 280px;
            height: auto;
            background-color:wheat;

            position: fixed;
            top:  260px;
            left: 600px;

            border-width: 10px;
            border-style: solid;
            border-color:wheat;
        }
        #reset{
            position: fixed;
            top: 400px;
            left: 620px;
        }
        #login1{
            position: fixed;
            top: 400px;
            left: 820px;
        }
        #title{
            position: fixed;
            top: 180px;
            left: 640px;

        }

    </style>

</head>
<body>
<!--action接的是登录的servlet-->
<div>
    <div>
        <h1 id="title">银行系统登录</h1>
    </div>
    <div id="login">
        <form method="post" action="login">
            <h4>银行卡号:<input type="text" name="id"/><br/></h4>
            <h4>银行密码:<input type="password" name="password"/><br/></h4>
            <input id="login1" type="submit" value="login" name="method">

            <input id="reset" type="reset" value="重置">
        </form>
    </div>
</div>
</body>
</html>

登录失败页面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 9:22
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>ERROR</title>
</head>
<body>
<a href="login.jsp"><h1>用户名或密码错误，点击重新登录</h1></a>
</body>
</html>

操作页面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 9:25
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>操作界面</title>

    <style type="text/css">
        body{
            background-color: #F5DEB3;
        }
        #center{
            width: 260px;
            position: absolute;
            top: 200px;
            left: 580px;
            border-radius: inherit;
        }
        .button{
            align-self: center;
        }

    </style>
</head>
<body>
<!--头部的div-->
<div id="head">
    <h1 align="center">操作界面</h1>
</div>
<div id="center">
    <form method="post" action="login">
        <h2 align="center">欢迎您${username}</h2>
        <a href="in.jsp"><input type="button"  value="存钱"></a><br/>
        <a href="get.jsp"><input type="button" value="取钱"></a><br/>
        <a href="view.jsp"><input type="button"  value="查看余额"><br/></a>
        <a href="changepassword.jsp"><input type="button"  value="修改密码"><br/></a>
        <input type="submit"  name="method" value="layout"><br/>
    </form>
</div>


</body>
</html>


取钱页面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 9:26
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>取钱操作</title>
    <style>
        body{
            background-color: #F5DEB3;
        }
        div{
            width: 300px;
            background-color: #F5DEB3;
            position: absolute;
            top: 200px;
            left: 580px;
        }
    </style>
</head>
<body>
<div>
    <h1>取款</h1>
    <form method="post" action="login">
        <h2>取钱金额:<input type="text" name="moneyin"></h2>
        <input type="reset" value="重置">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<input id="click" type="submit" name="method" value="get">
    </form>
</div>
</body>
</html>

取钱失败页面 / 取钱成功页面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 9:42
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>取钱失败</title>
</head>
<body>
<a href="service.jsp"><h1>取钱失败，余额不足，点击跳转到操作页面</h1></a>
</body>
</html>

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 9:41
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>取钱成功</title>
</head>
<body>
<a href="service.jsp"><h1>取钱成功，点击跳转到操作页面</h1></a>
</body>
</html>

存钱界面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 10:16
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>存钱操作</title>
    <style>
        body{
            background-color: #F5DEB3;
        }
        div{
            width: 300px;
            background-color: #F5DEB3;
            position: absolute;
            top: 200px;
            left: 580px;
        }
    </style>
</head>
<body>
<div>
    <h1>存款</h1>
    <form method="post" action="login">
        <h2>存储金额:<input type="text" name="moneyin"></h2>
        <input type="hidden" name="moneyin">
        <input type="reset" value="重置">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<input id="click" type="submit" name="method" value="in">
    </form>
</div>
</body>
</html>
<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 10:16
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>存钱操作</title>
    <style>
        body{
            background-color: #F5DEB3;
        }
        div{
            width: 300px;
            background-color: #F5DEB3;
            position: absolute;
            top: 200px;
            left: 580px;
        }
    </style>
</head>
<body>
<div>
    <h1>存款</h1>
    <form method="post" action="login">
        <h2>存储金额:<input type="text" name="moneyin"></h2>
        <input type="hidden" name="moneyin">
        <input type="reset" value="重置">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<input id="click" type="submit" name="method" value="in">
    </form>
</div>
</body>
</html>

存钱成功界面/存钱失败页面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 10:22
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>存钱成功</title>
</head>
<body>
<a href="service.jsp"><h1>存钱成功，点击跳转到操作页面</h1></a>
</body>
</html>

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 10:23
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>存钱失败</title>
</head>
<body>
<a href="service.jsp"><h1>存钱失败，点击跳转到操作页面</h1></a>
</body>
</html>

修改密码页面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 10:45
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>修改密码</title>
    <style type="text/css">
        body{
            background-color: #FAEBD7;
        }
        div{
            position: absolute;
            top: 200px;
            left: 600px;
        }
    </style>
</head>
<body>
<div>
    <h1>修改密码</h1>
    <form action="login" method="post">
        <h3>请输入旧密码:<input type="text" name="oldpassword"></h3>
        <h3>请输入新密码:<input type="text" name="newpassword"></h3>
        <input type="submit" value="重置"/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<input type="submit" value="change" name="method"/>
    </form>
</div>
</body>
</html>

修改密码成功页面 / 修改密码失败页面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 10:52
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>修改密码成功</title>
</head>
<body>
<a href="login.jsp"><h1>修改密码成功，请点击重新登陆</h1></a>
</body>
</html>

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 10:51
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>修改密码失败</title>
</head>
<body>
<a href="changepassword.jsp"><h1>旧密码错误，点击重新输入</h1></a>
</body>
</html>

查看余额页面

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<%--
  Created by IntelliJ IDEA.
  User: Lenovo
  Date: 2021/11/30
  Time: 10:11
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <title>查看存款</title>
    <style type="text/css">
        body{
            background-color: antiquewhite;

        }
        div{
            position: absolute;
            top: 200px;
            left: 600px;
        }
    </style>
</head>
<body>
<div>
    <h1>查看存款</h1>
    <form action="login" method="post">
        <h2>客户${username}，您的存款数目为${money}元</h2><br/>
        <a href="service.jsp"><h4>点击返回到操作页面</h4></a>
    </form>
</div>
</body>
</html>


后端代码

所有的依赖

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<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>org.example</groupId>
  <artifactId>BankSystem</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>BankSystem Maven Webapp</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <!--mysql依赖-->
    <!-- https://mvnrepository.com/artifact/org.wisdom-framework/mysql-connector-java -->
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
      <version>8.0.27</version>
    </dependency>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>javax.servlet-api</artifactId>
      <version>4.0.1</version>
      <scope>provided</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>javax.servlet.jsp-api</artifactId>
      <version>2.3.3</version>
      <scope>provided</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.apache.taglibs/taglibs-standard-impl -->
    <dependency>
      <groupId>org.apache.taglibs</groupId>
      <artifactId>taglibs-standard-impl</artifactId>
      <version>1.2.5</version>
      <scope>runtime</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/javax.servlet.jsp.jstl/jstl -->
    <dependency>
      <groupId>javax.servlet.jsp.jstl</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>
    <dependency>
      <groupId>xml-apis</groupId>
      <artifactId>xml-apis</artifactId>
      <version>1.3.04</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.apache.taglibs/taglibs-standard-impl -->
    <dependency>
      <groupId>org.apache.taglibs</groupId>
      <artifactId>taglibs-standard-impl</artifactId>
      <version>1.2.5</version>
      <scope>runtime</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/org.junit.jupiter/junit-jupiter-api -->
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter-api</artifactId>
      <version>5.8.1</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.testng</groupId>
      <artifactId>testng</artifactId>
      <version>RELEASE</version>
      <scope>compile</scope>
    </dependency>
    <!-- https://mvnrepository.com/artifact/commons-fileupload/commons-fileupload -->
    <dependency>
      <groupId>commons-fileupload</groupId>
      <artifactId>commons-fileupload</artifactId>
      <version>1.4</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/commons-io/commons-io -->
    <dependency>
      <groupId>commons-io</groupId>
      <artifactId>commons-io</artifactId>
      <version>2.11.0</version>
    </dependency>


  </dependencies>

  <build>
    <finalName>BankSystem</finalName>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-war-plugin</artifactId>
          <version>3.2.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

web.xml

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<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                      http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0"
         metadata-complete="true">
    <welcome-file-list>
        <welcome-file>/login.jsp</welcome-file>
    </welcome-file-list>
    <servlet>
        <servlet-name>login</servlet-name>
        <servlet-class>com.dwx.servlet.customerServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>login</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
</web-app>

后端代码

DAO层

basedao

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package com.dwx.dao;

import java.io.IOException;
import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

//这是一个最基础的Dao类 是用来和数据库进行交互的
//通过分析 我们需要用到的jdbc操作 包括 查 改
public class BaseDao {
    //获取和数据库的联结
    public static String driver;
    public static String url;
    public static String username;
    public static String password;
    //通过重定向 到db.propertries中获取到数据
    //定义的static参数 通过static代码块 对其进行初始化
    static{
        InputStream stream = BaseDao.class.getClassLoader().getResourceAsStream("db.properties");
        Properties properties = new Properties();
        try {
            properties.load(stream);
        } catch (IOException e) {
            e.printStackTrace();
        }
        driver = properties.getProperty("driver");
        url = properties.getProperty("url");
        username = properties.getProperty("username");
        password = properties.getProperty("password");
    }
    //与数据库进行链接
    public static Connection getConnection(){
        Connection connection = null;
        try {
            Class.forName(driver);
            connection = DriverManager.getConnection(url, username, password);
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        }

        return connection;
    }
    //创建用于改的execute
    //编写查询公共类
    public static ResultSet exectue(Connection connection, PreparedStatement prepareStatement, ResultSet resultSet, String sql, Object[] params) throws Exception {
        try {
            prepareStatement = connection.prepareStatement(sql);
            //不清楚这里的prepareStatement与setStatement有啥区别
            //prepareStream是预编译 是解决数据库泄露问题时讲过的
            for (int i = 0; i < params.length; i++) {
                prepareStatement.setObject(i + 1, params[i]);
            }
        } catch (Exception throwables) {
            throwables.printStackTrace();
        }
        resultSet = prepareStatement.executeQuery();
        return resultSet;
    }

    //增删改公共方法
    public static int exectue(Connection connection,PreparedStatement prepareStatement,String sql,Object[] params) throws Exception {
        try {
            prepareStatement = connection.prepareStatement(sql);
            //不清楚这里的prepareStatement与setStatement有啥区别
            for (int i=0;i<params.length;i++){
                prepareStatement.setObject(i+1,params[i]);
            }
        } catch (Exception throwables) {
            throwables.printStackTrace();
        }
        int updataRows = prepareStatement.executeUpdate();
        return  updataRows;


    }
    //释放资源
    public static boolean closeResource(Connection connection,PreparedStatement preparedStatement,ResultSet resultSet) throws Exception {
        boolean flag=true;
        if (resultSet!=null){
            resultSet.close();
            resultSet = null;
        }
        if (preparedStatement!=null){
            preparedStatement.close();
            preparedStatement=null;
        }
        if (connection!=null){
            connection.close();
        }
        return flag;

    }

}

monyDao

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package com.dwx.dao.money;

import java.sql.SQLException;

public interface moneyDao {
    //对于金钱的操作有三种 产看余额 存款 取款
    //查看余额 就是一个查询语句 返回值是int类型 money
    //通过 ID 和 Password来获得余额
    double getMoney(String ID,String password) throws SQLException;
    //存取款 ID password moneyIn
    boolean changeMoney(String ID,String password,double money,double moneyIn);
}

moneyDaoImp

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package com.dwx.dao.money;

import com.dwx.dao.BaseDao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class moneyDaoImp implements moneyDao {
    @Override
    public double getMoney(String ID, String password) throws SQLException {
        //先进行数据库链接
        Connection connection;
        connection = BaseDao.getConnection();
        double money=0;
        //写预编译sql
        PreparedStatement pstm=null;
        String sql = "SELECT money FROM bank_system WHERE ID = ? AND Password = ?";
        //编写一个参数集 用来传递参数
        Object[] param = {ID,password};
        ResultSet result = null;
        //编写一个resul来获得查询的返回值
        try {
            result = BaseDao.exectue(connection,pstm,result,sql,param);
        } catch (Exception e) {
            e.printStackTrace();
        }
        //得到了result
        if (result.next()){
            money = result.getDouble("money");
        }
        return money;
    }

    @Override
    public boolean changeMoney(String ID, String password,double money,double moneyIn) {
        if (money+moneyIn<0){
            return false;
        }
        boolean flag = false;
        //创建连接
        Connection connection;
        connection = BaseDao.getConnection();
        //编写预编译SQL
        int r = 0;
        PreparedStatement pstm = null;
        String sql = "UPDATE bank_system SET money = ? WHERE ID = ? AND Password = ?";
        //编写param表示参数集
        //这里 用money + moneyIn表示改变后的值 若moneyIn为正 则就是存储 要是负 则是取钱
        Object[] param = {money+moneyIn,ID,password};
        //调用Base进行改值
        try {
            r = BaseDao.exectue(connection,pstm,sql,param);
        } catch (Exception e) {
            e.printStackTrace();
        }
        if (r!=0){
            flag=true;
        }
        System.out.println("Dao"+flag);
        return flag;
    }
}

userDao

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package com.dwx.dao.user;

import java.sql.SQLException;

//这个抽象类 主要是对user进行操作 如 修改密码 增加用户 删除用户 等等
public interface userDao {
    //修改密码 修改密码需要用到 ID 和 old_password 进行比较后才能修改
    //修改密码 返回布尔类型 表示是否修改成功
    boolean changePassword(String ID,String oldPassword,String newPassword);
    //用户登录 就是去数据库查询是否有此人 如有此人 则返回username 需要获得ID，password
    String login(String ID,String password) throws SQLException;

}

userDaoImp

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package com.dwx.dao.user;

import com.dwx.dao.BaseDao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class userDaoimp implements userDao{
    @Override
    public boolean changePassword(String ID, String oldPassword,String newPassword) {
        //获得链接
        boolean flag = false;
        int resultSet = 0;
        Connection connection;
        connection = BaseDao.getConnection();
        //预编译sql
        PreparedStatement pstm = null;
        String sql = "UPDATE bank_system SET Password=? WHERE ID=? AND Password=?";
        //设置sql要插入的参数
        Object[] param = {newPassword,ID,oldPassword};
        try {
            resultSet = BaseDao.exectue(connection,pstm,sql,param);
        } catch (Exception e) {
            e.printStackTrace();
        }
        if (resultSet!=0){
            flag=true;
        }
        //关闭开启的资源
        try {
            BaseDao.closeResource(connection,pstm,null);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return flag;
    }

    @Override
    public String login(String ID, String password) throws SQLException {
        Connection connection;
        //注意 不要忘记connection
        connection = BaseDao.getConnection();
        String username=null;
        //预编译一个SQL 只需要一个SELECT
        PreparedStatement pstm=null;
        //准备一个结果集 这个查询是要获得结果集的
        String sql = "SELECT * From bank_system WHERE ID = ? AND Password = ?";
        //创建一个param参数
        Object[] param = {ID,password};
        //用一个result来存储查询到的结果集
        ResultSet resultSet = null;
        try {
            resultSet = BaseDao.exectue(connection,pstm,resultSet,sql,param);
        } catch (Exception e) {
            e.printStackTrace();
        }
        assert resultSet != null;
        if (resultSet.next()){
            username = resultSet.getString("username");
        }
        return username;
    }
}

POJO

映射类

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package com.dwx.pojo;
//这个类是映射到数据库中bank_system这个表
public class bank_system {
    //创造几个对象 对应数据库中的几个参数
    //设置的都是私有对象 需要通过set和get获取值
    private int ID;
    private String Password;
    private String username;
    private int money;

    public int getID() {
        return ID;
    }

    public void setID(int ID) {
        this.ID = ID;
    }

    public String getPassword() {
        return Password;
    }

    public void setPassword(String password) {
        Password = password;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public int getMoney() {
        return money;
    }

    public void setMoney(int money) {
        this.money = money;
    }
}

service层

userservice

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package com.dwx.service.user;
//对于用户的一些操作

public interface userService {

    //修改用户的密码 修改密码需要得到并传递给dao层 ID（int） newPasswor(String) oldPasswor(String)
    //返回值类型为 boolen
     boolean  changePasswordService(String ID,String oldPassword,String newPassword);
     //登录 需要给Dao ID Password 需要返回给test username
    String login(String ID,String passWord);

}

userserviceImp

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package com.dwx.service.user;

import com.dwx.dao.user.userDaoimp;

import java.sql.SQLException;

public class userServiceImp implements userService{
    @Override
    public  boolean changePasswordService(String ID, String oldPassword, String newPassword) {
        boolean flag;
        userDaoimp daoimp = new userDaoimp();
        flag = daoimp.changePassword(ID,oldPassword,newPassword);
        return flag;
    }

    @Override
    public String login(String ID, String passWord) {
        String username = null;
        userDaoimp daoimp = new userDaoimp();
        try {
            username = daoimp.login(ID,passWord);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        }
        return username;
    }
}

servlet层

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package com.dwx.servlet;

import com.dwx.service.money.moneyServiceImp;
import com.dwx.service.user.userServiceImp;

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

public class customerServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
        String method = req.getParameter("method");
        System.out.println(method);
        switch (method) {
            case "login":
                login(req, resp);
                break;
            case "get":
                getmoney(req, resp);
                break;
            case "in":
                insertmoney(req, resp);
                break;
            case "layout":
                logout(req, resp);
                break;
            case "change":
                changepassword(req, resp);
                break;
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp){
        doGet(req, resp);
    }
    public void login(HttpServletRequest req, HttpServletResponse resp){
        String id = req.getParameter("id");
        System.out.println(id);
        String password = req.getParameter("password");
        System.out.println(password);
        double money;
        //用得到的数据进行联结
        userServiceImp userServiceImp = new userServiceImp();
        moneyServiceImp moneyServiceImp = new moneyServiceImp();
        money = moneyServiceImp.getMoney(id,password);
        //登录
        String username = userServiceImp.login(id,password);
        //如果登录成功就跳转到service.jsp页面
        //如果登陆失败 就跳转到error.jsp页面
        if (username==null){
            try {
                resp.sendRedirect("error.jsp");
            } catch (IOException ignored) {

            }
        }else {
            //如果联结成功 就把用户名 账号 密码 都放到session里边 以便其他的程序使用
            req.getSession().setAttribute("id",id);
            req.getSession().setAttribute("password",password);
            req.getSession().setAttribute("username",username);
            req.getSession().setAttribute("money",money);
            try {
                resp.sendRedirect("service.jsp");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
    public void getmoney(HttpServletRequest req,HttpServletResponse resp){
        //经过登录操作 已经把id,password,money等数据都存放到session里了 需要的话直接去session里拿
        String id = (String) req.getSession().getAttribute("id");
        String password = (String) req.getSession().getAttribute("password");
        double money = (Double) req.getSession().getAttribute("money");
        System.out.println(id);
        System.out.println(password);
        System.out.println(money);
        //从前端获取要取出的数值 再去service层进行操作
        double moneyin = Double.parseDouble(req.getParameter("moneyin"));
        //设置一个flag来分辨是否取钱成功
        boolean flag;
        moneyServiceImp moneyServiceImp = new moneyServiceImp();
        flag = moneyServiceImp.changeMoney(id,password,money,-moneyin);
        //如果取钱成功 跳转到取钱成功页面
        //取钱成功 及时更改session里的money的值
        req.getSession().setAttribute("money",moneyServiceImp.getMoney(id,password));
        if (flag){
            try {
                resp.sendRedirect("getSuccess.jsp");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        //如果取钱失败 跳转到取钱失败页面
        else {
            try {
                resp.sendRedirect("getError.jsp");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    public void insertmoney(HttpServletRequest req,HttpServletResponse resp){
        //与取款一样 存款需要从session里边获取数值
        String id = (String) req.getSession().getAttribute("id");
        String password = (String) req.getSession().getAttribute("password");
        double money = (Double) req.getSession().getAttribute("money");
        //再拿到前端输入的需要存款的数值
        double moneyin = Double.parseDouble(req.getParameter("moneyin"));
        //调用service层对数据进行操作哦
        moneyServiceImp moneyServiceImp = new moneyServiceImp();
        //设置一个布尔值 来判断是否操作成功
        boolean flag;
        flag = moneyServiceImp.changeMoney(id,password,money,moneyin);
        if (flag){
            //如果操作成功 跳转到存款成功页面 并且更新session中money的值
            req.getSession().setAttribute("money",moneyServiceImp.getMoney(id,password));
            try {
                resp.sendRedirect("insuccess.jsp");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }else {
            //如果没有成功 则跳转到存钱失败页面
            try {
                resp.sendRedirect("inError.jsp");
            } catch (IOException e) {
                e.printStackTrace();
            }

        }

    }
    public void logout(HttpServletRequest req, HttpServletResponse resp){
        //退出操作
        //退出操作的具体思路就是 将session里的id和password都换成null并且跳转到登录页面
        req.getSession().setAttribute("id",null);
        req.getSession().setAttribute("password",null);
        try {
            resp.sendRedirect("login.jsp");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public void changepassword(HttpServletRequest req, HttpServletResponse resp){
        //从session里获得数据
        String id = (String) req.getSession().getAttribute("id");
        String password = (String) req.getSession().getAttribute("password");
        //从前端获得数据
        String passwordin = req.getParameter("oldpassword");
        System.out.println(passwordin);
        String newpassword = req.getParameter("newpassword");
        System.out.println(newpassword);
        //如果前端获取的oldpassword与实际的password不同 跳转到Error页面
        //如果通过了 就往下继续执行
        userServiceImp userServiceImp = new userServiceImp();
        //创造一个布尔值来标记是否修改成功
        boolean flag;
        flag = userServiceImp.changePasswordService(id,password,newpassword);
        if (flag)
        {
            //如果修改成功 就跳转到成功页面
            try {
                resp.sendRedirect("changesuccess.jsp");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }else {
            //如果没成功就送到失败页面
            try {
                resp.sendRedirect("changeError.jsp");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }
}

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