本笔记包括两个案例，分别是用户登录、验证码。

案例：用户登录

接着《HTTP：超文本传输协议》、《HTTP请求信息数据 - Request》的学习，
现在记录一份案例学习。

用户需求

编写 login.html 登录页面，并且有 username & password 两个输入框
使用 Druid 数据库连接池技术，操作 MySQL，day14数据库中user表
使用 JdbcTemplate 技术封装 JDBC
登录成功跳转到 SuccessServlet 展示：登录成功！用户名,欢迎您
登录失败跳转到 FailServlet 展示：登录失败，用户名或密码错误

分析

步骤

创建项目，导入html页面，配置文件，jar包
创建数据库环境
创建包cn.itcast.domain,创建类User
创建包cn.itcast.util,编写工具类JDBCUtils
创建包cn.itcast.dao,创建类UserDao,提供login方法
编写cn.itcast.web.servlet.LoginServlet类
编写FailServlet和SuccessServlet类
BeanUtils工具类，简化数据封装

一、创建项目，导入html页面，配置文件，jar包

新建Module

web文件夹下创建login.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>用户登录</title>
</head>
<body>
<form action="/day14_test/loginServlet" method="post">
    用户名:<input type="text" name="username"> <br>
    密码:<input type="password" name="password"><br>

    <input type="submit" value="登录">

</form>
</body>
</html>

这里的login.html中form表单的action路径的写法：虚拟目录+Servlet的资源路径是
虚拟目录+Servlet的资源路径

关于《html中form表单的action路径的写法》

将Druid配置文件druid.properties导入到src文件下

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///day14
username=root
password=root
initialSize=5
maxActive=10
maxWait=3000

导入jar包到Web的WEB-INF文件中

在项目的web文件夹下创建文件夹WEB-INF，将lib文件夹粘贴进去

并把jar包加入到工作空间里

二、创建数据库环境

打开Navicat，创建数据库和数据表

CREATE DATABASE	day14;
USE day14;

CREATE TABLE USER(
	id INT PRIMARY KEY AUTO_INCREMENT,
	username VARCHAR(32) UNIQUE NOT NULL,
	PASSWORD VARCHAR(32) NOT NULL
);

插入一条记录

三、创建包cn.itcast.domain,创建类User

右键项目的src文件，New一个包cn.itcast.domain
在包下，New一个User.java

package cn.itcast.domain;

/**
 * 用户的实体类
 */
public class User {

    private int id;
    private String username;
    private String password;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getUsername() {
        return username;
    }

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

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

四、创建包cn.itcast.util,编写工具类JDBCUtils

New一个包cn.itcast.util
New一个JDBCUtils.java

package cn.itcast.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.ConnectionEvent;
import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

/**
 * JDBC的工具类 使用Durid连接池
 */
public class JDBCUtils {

    private static DataSource ds;

    static {

        try {
            //1.加载配置文件
            Properties pro = new Properties();
            //使用ClassLoader加载配置文件，获取字节输入流
            InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");
            pro.load(is);

            //2.初始化连接池对象
            ds = DruidDataSourceFactory.createDataSource(pro);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }


    }

    /**
     * 获取连接池对象
     */
    public static DataSource getDataSource(){
        return ds;
    }

    /**
     * 获取连接池Connection对象
     */
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }
}

五、创建包cn.itcast.dao,创建类UserDao,提供login方法

New一个包cn.itcast.dao
New一个UserDao.java

package cn.itcast.Dao;

import cn.itcast.domain.User;
import cn.itcast.util.JDBCUtils;
import com.alibaba.druid.util.JdbcUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

/**
 * 操作数据库中User表的类
 */
public class UserDao {

    // 声明JDBCTemplate对象公用
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());
    /**
     * 登录方法
     * @param loginUser 只有用户名和密码
     * @return User包含用户全部数据；没有查询到，返回null
     */
    public User login(User loginUser) {
        try {
            //1.编写SQL
            String sql = "select * from user where username = ? and password = ?";
            //2.调用query方法
            User user = template.queryForObject(sql,
                    new BeanPropertyRowMapper<User>(User.class),
                    loginUser.getUsername(), loginUser.getPassword());
            return user;
        } catch (DataAccessException e) {
            e.printStackTrace(); // 记录日志，后期写入文件里，不会总在控制台打印
            return null;
        }
    }
}

测试一下UserDao
New一个包cn.itcast.test，New一个UserDaoTest.java

package cn.itcast.test;

import cn.itcast.Dao.UserDao;
import cn.itcast.domain.User;
import org.junit.Test;

/**
 * @Classname UserDaoTest
 * @Description TODO
 * @Date 2020/2/23 下午 1:00
 * @Created by jerry
 */
public class UserDaoTest {
    @Test
    public void testLogin(){

        User loginuser = new User();
        loginuser.setUsername("superbaby");
        loginuser.setPassword("123");

        UserDao dao = new UserDao();
        User user = dao.login(loginuser);

        System.out.println(user);
    }

}

run后，控制台输出

这个@Test部分，遇到了一些问题，就顺便记录在《创建@Test测试Druid连接池时的问题》里面。

六、编写cn.itcast.web.servlet.LoginServlet类

New一个包cn.itcast.web.servlet
New一个LoginServlet.java

package cn.itcast.web.servlet;

import cn.itcast.Dao.UserDao;
import cn.itcast.domain.User;
import cn.itcast.test.UserDaoTest;

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;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.设置编码
        req.setCharacterEncoding("utf-8");
        //2.获取请求参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //3.封装user对象
        User loginUser = new User();
        loginUser.setUsername("username");
        loginUser.setPassword("password");

        //4.调用UserDao的login方法
        UserDao dao = new UserDao();
        User user = dao.login(loginUser); //真正获取到的user

        //5.判断user
        if(user == null){
            //登录失败
            req.getRequestDispatcher("/failServlet").forward(req,resp); //转发
        }else{
            //登录成功
            //存储数据
            req.setAttribute("user",user);
            //转发
            req.getRequestDispatcher("/successServlet").forward(req,resp);
        }

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

七、编写FailServlet和SuccessServlet类

New一个FailServlet.java

package cn.itcast.web.servlet;

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;

/**
 * @Classname failServlet
 * @Description TODO
 * @Date 2020/2/23 下午 3:38
 * @Created by jerry
 */
@WebServlet("/failServlet")
public class FailServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //给页面写一句话

        //设置页面编码
        response.setContentType("text/html;charset=utf-8");
        //输出
        response.getWriter().write("登录失败，用户名或密码错误");
    }

}

New一个SuccessServlet.java

package cn.itcast.web.servlet;

import cn.itcast.domain.User;

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;

/**
 * @Classname successServlet
 * @Description TODO
 * @Date 2020/2/23 下午 3:38
 * @Created by jerry
 */
@WebServlet("/successServlet")
public class SuccessServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取request域中共享的user对象
        User user = (User) request.getAttribute("user");

        if(user != null){
            //给页面写一句话

            //设置页面编码
            response.setContentType("text/html;charset=utf-8");
            //输出
            response.getWriter().write("登录失败，用户名或密码错误");
        }

    }

}

八、测试

浏览器访问：http://localhost/day14_test/login.html

九、BeanUtils工具类，简化数据封装

在LoginServlet.java中使用BeanUtils工具类

package cn.itcast.web.servlet;

import cn.itcast.Dao.UserDao;
import cn.itcast.domain.User;
import cn.itcast.test.UserDaoTest;
import org.apache.commons.beanutils.BeanUtils;

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;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.设置编码
        req.setCharacterEncoding("utf-8");
        /*//2.获取请求参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        //3.封装user对象
        User loginUser = new User();
        loginUser.setUsername(username);
        loginUser.setPassword(password);*/

        //2.获取所有请求参数
        Map<String, String[]> map = req.getParameterMap();
        //3.创建User对象
        User loginUser = new User();
        //3-2.使用BeanUtils封装
        try {
            BeanUtils.populate(loginUser,map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        //4.调用UserDao的login方法
        UserDao dao = new UserDao();
        User user = dao.login(loginUser); //真正获取到的user

        //5.判断user
        if(user == null){
            //登录失败
            req.getRequestDispatcher("/failServlet").forward(req,resp); //转发
        }else{
            //登录成功
            //存储数据
            req.setAttribute("user",user);
            //转发
            req.getRequestDispatcher("/successServlet").forward(req,resp);
        }

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

关于BeanUtils的更多使用，看下一篇笔记《BeanUtils的基本使用》。

与本笔记相关的资源：

链接: https://pan.baidu.com/s/1pV1ArOotLcoH9mKYABEm5g 提取码: w9h8

案例：验证码

接着《JSP&Cookie&Session技术》的学习，

现在记录一份案例的学习。

用户需求

访问带有验证码的登录页面login.jsp
用户输入用户名，密码以及验证码，
- 如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误
- 如果验证码输入有误，跳转登录页面，提示：验证码错误
- 如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您

分析

设置request编码
获取参数
获取生成的验证码
将用户信息封装到User对象
判断程序生成的验证码和用户输入的验证码是否一致。从session中获取程序生成的验证码
一致：再判断用户名和密码是否正确
- 正确：
  - 1.登陆成功
  - 2.存储数据到session中
  - 3.跳转（重定向）到success.jsp
- 不正确：
  - 1.给提示信息：用户名或密码错误
  - 2.跳转（转发）到登录页面
不一致：
- 1.给用户提示信息：验证码错误
- 2.存储提示信息到request
- 3.跳转（转发）到登录页面
login.jsp显示错误信息，从request域中获取

Code

CheckCodeServlet.java

package cn.itcast.servlet;

import javax.imageio.ImageIO;
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.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


        int width = 100;
        int height = 50;

        //1.创建一对象，在内存中图片(验证码图片对象)
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);


        //2.美化图片
        //2.1 填充背景色
        Graphics g = image.getGraphics();//画笔对象
        g.setColor(Color.PINK);//设置画笔颜色
        g.fillRect(0,0,width,height);

        //2.2画边框
        g.setColor(Color.BLUE);
        g.drawRect(0,0,width - 1,height - 1);

        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        //生成随机角标
        Random ran = new Random();
        StringBuilder sb = new StringBuilder();
        for (int i = 1; i <= 4; i++) {
            int index = ran.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);//随机字符
            sb.append(ch);

            //2.3写验证码
            g.drawString(ch+"",width/5*i,height/2);
        }
        String checkCode_session = sb.toString();
        //将验证码存入session
        request.getSession().setAttribute("checkCode_session",checkCode_session);

        //2.4画干扰线
        g.setColor(Color.GREEN);

        //随机生成坐标点

        for (int i = 0; i < 10; i++) {
            int x1 = ran.nextInt(width);
            int x2 = ran.nextInt(width);

            int y1 = ran.nextInt(height);
            int y2 = ran.nextInt(height);
            g.drawLine(x1,y1,x2,y2);
        }


        //3.将图片输出到页面展示
        ImageIO.write(image,"jpg",response.getOutputStream());


    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>用户登录</title>

    <!--点击刷新验证码-->
    <script>
        window.onload = function(){
            document.getElementById("img").onclick = function(){
                this.src="/day16/checkCodeServlet?time="+new Date().getTime();
            }
        }


    </script>
    <style>
        div{
            color: red;
        }

    </style>
</head>
<body>

    <form action="/day16/loginServlet" method="post">
        <table>
            <tr>
                <td>用户名</td>
                <td><input type="text" name="username"></td>
            </tr>
            <tr>
                <td>密码</td>
                <td><input type="password" name="password"></td>
            </tr>
            <tr>
                <td>验证码</td>
                <td><input type="text" name="checkCode"></td>
            </tr>
            <tr>
                <td colspan="2"><img id="img" src="/day16/checkCodeServlet"></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="登录"></td>
            </tr>
        </table>


    </form>

    <div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%></div>
    <div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %></div>
    
    <!-- 等同于 EL表达式。有信息就打印输出，没有就显示空字符串。
    	${requestScope.cc_error}
    	${requestScope.login.error}
    -->

</body>
</html>

LoginServlet.java

package cn.itcast.servlet;

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 javax.servlet.http.HttpSession;
import java.io.IOException;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.设置request编码
        request.setCharacterEncoding("utf-8");
        //2.获取参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String checkCode = request.getParameter("checkCode");
        //3.先获取生成的验证码
        HttpSession session = request.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");
        //删除session中存储的验证码
        session.removeAttribute("checkCode_session");
        //3.先判断验证码是否正确
        if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){
            //忽略大小写比较
            //验证码正确
            //判断用户名和密码是否一致
            if("zhangsan".equals(username) && "123".equals(password)){//需要调用UserDao查询数据库
                //登录成功
                //存储信息，用户信息
                session.setAttribute("user",username);
                //重定向到success.jsp
                response.sendRedirect(request.getContextPath()+"/success.jsp");
            }else{
                //登录失败
                //存储提示信息到request
                request.setAttribute("login_error","用户名或密码错误");
                //转发到登录页面
                request.getRequestDispatcher("/login.jsp").forward(request,response);
            }


        }else{
            //验证码不一致
            //存储提示信息到request
            request.setAttribute("cc_error","验证码错误");
            //转发到登录页面
            request.getRequestDispatcher("/login.jsp").forward(request,response);

        }

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>成功登录</title>
</head>
<body>

    <h1><%=request.getSession().getAttribute("user")%>,欢迎您</h1>

</body>
</html>

案例：用户登录

用户需求

分析

步骤

一、创建项目，导入html页面，配置文件，jar包

二、创建数据库环境

三、创建包cn.itcast.domain,创建类User

四、创建包cn.itcast.util,编写工具类JDBCUtils

五、创建包cn.itcast.dao,创建类UserDao,提供login方法

六、编写cn.itcast.web.servlet.LoginServlet类

七、编写FailServlet和SuccessServlet类

八、测试

九、BeanUtils工具类，简化数据封装

案例：验证码

用户需求

分析

Code

CheckCodeServlet.java

LoginServlet.java

success.jsp

Demo

视频详解