Servlet案例3：验证码功能

2022-10-21 18:32:55

这里介绍简单的验证码功能

动态生成图片

一个简单的页面：

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

<script type="text/javascript">

    function changeImg(obj){

        obj.src="/WEB4/checkImg?time="+new Date().getTime();

    }

</script>

</head>

<body>

    <form action="/WEB13/login" method="post">

        用户名：<input type="text" name="username"><br/>

        密码：<input type="password" name="password"><br/>

        验证码：<input type="text" name="username"><img onclick="changeImg(this)" src="/WEB4/checkImg"><br/>

        <input type="submit" value="登录"><br/>

    </form>

</body>

</html>

简单的JS代码实现点击验证码图片刷新

验证码功能：

package demo;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

import java.awt.Graphics2D;

import java.awt.image.BufferedImage;

import java.io.BufferedReader;

import java.io.FileReader;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import java.util.Random;

import javax.imageio.ImageIO;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * 验证码生成程序

 *

 *

 *

 */

public class CheckImgServlet extends HttpServlet {

    // 集合中保存所有成语

    private List<String> words = new ArrayList<String>();

    @Override

    public void init() throws ServletException {

        // 初始化阶段，读取new_words.txt

        // web工程中读取 文件，必须使用绝对磁盘路径

        String path = getServletContext().getRealPath("/WEB-INF/new_words.txt");

        try {

            BufferedReader reader = new BufferedReader(new FileReader(path));

            String line;

            while ((line = reader.readLine()) != null) {

                words.add(line);

            }

            reader.close();

        } catch (IOException e) {

            e.printStackTrace();

        }

    }

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        // 禁止缓存

        // response.setHeader("Cache-Control", "no-cache");

        // response.setHeader("Pragma", "no-cache");

        // response.setDateHeader("Expires", -1);

        int width = 120;

        int height = 30;

        // 步骤一 绘制一张内存中图片

        BufferedImage bufferedImage = new BufferedImage(width, height,

                BufferedImage.TYPE_INT_RGB);

        // 步骤二 图片绘制背景颜色 ---通过绘图对象

        Graphics graphics = bufferedImage.getGraphics();// 得到画图对象 --- 画笔

        // 绘制任何图形之前 都必须指定一个颜色

        graphics.setColor(getRandColor(200, 250));

        graphics.fillRect(0, 0, width, height);

        // 步骤三 绘制边框

        graphics.setColor(Color.WHITE);

        graphics.drawRect(0, 0, width - 1, height - 1);

        // 步骤四 四个随机数字

        Graphics2D graphics2d = (Graphics2D) graphics;

        // 设置输出字体

        graphics2d.setFont(new Font("宋体", Font.BOLD, 18));

        Random random = new Random();// 生成随机数

        int index = random.nextInt(words.size());

        String word = words.get(index);// 获得成语

        // 定义x坐标

        int x = 10;

        for (int i = 0; i < word.length(); i++) {

            // 随机颜色

            graphics2d.setColor(new Color(20 + random.nextInt(110), 20 + random

                    .nextInt(110), 20 + random.nextInt(110)));

            // 旋转 -30 --- 30度

            int jiaodu = random.nextInt(60) - 30;

            // 换算弧度

            double theta = jiaodu * Math.PI / 180;

            // 获得字母数字

            char c = word.charAt(i);

            // 将c 输出到图片

            graphics2d.rotate(theta, x, 20);

            graphics2d.drawString(String.valueOf(c), x, 20);

            graphics2d.rotate(-theta, x, 20);

            x += 30;

        }

        // 将验证码内容保存session

        request.getSession().setAttribute("checkcode_session", word);

        // 步骤五 绘制干扰线

        graphics.setColor(getRandColor(160, 200));

        int x1;

        int x2;

        int y1;

        int y2;

        for (int i = 0; i < 30; i++) {

            x1 = random.nextInt(width);

            x2 = random.nextInt(12);

            y1 = random.nextInt(height);

            y2 = random.nextInt(12);

            graphics.drawLine(x1, y1, x1 + x2, x2 + y2);

        }

        // 将上面图片输出到浏览器 ImageIO

        graphics.dispose();// 释放资源

        //将图片写到response.getOutputStream()中

        ImageIO.write(bufferedImage, "jpg", response.getOutputStream());

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doGet(request, response);

    }

    /**

     * 取其某一范围的color

     *

     * @param fc

     *            int 范围参数1

     * @param bc

     *            int 范围参数2

     * @return Color

     */

    private Color getRandColor(int fc, int bc) {

        // 取其随机颜色

        Random random = new Random();

        if (fc > 255) {

            fc = 255;

        }

        if (bc > 255) {

            bc = 255;

        }

        int r = fc + random.nextInt(bc - fc);

        int g = fc + random.nextInt(bc - fc);

        int b = fc + random.nextInt(bc - fc);

        return new Color(r, g, b);

    }

}

这里采用的是成语的验证码，将很多个成语存到WEB-INF目录下一个文本中，每行一个即可

补上web.xml配置文件

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

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

  <display-name>WEB4</display-name>

  <welcome-file-list>

    <welcome-file>index.html</welcome-file>

    <welcome-file>index.htm</welcome-file>

    <welcome-file>index.jsp</welcome-file>

    <welcome-file>default.html</welcome-file>

    <welcome-file>default.htm</welcome-file>

    <welcome-file>default.jsp</welcome-file>

  </welcome-file-list>

  <servlet>

    <description></description>

    <display-name>CheckImgServlet</display-name>

    <servlet-name>CheckImgServlet</servlet-name>

    <servlet-class>demo.CheckImgServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>CheckImgServlet</servlet-name>

    <url-pattern>/checkImg</url-pattern>

  </servlet-mapping>

</web-app>

接下来是验证码校验功能：

session的简单应用

上边验证码中已经将验证码加入了session中：

request.getSession().setAttribute("checkcode_session", word);

接下来就是验证码的校验：

package login;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        request.setCharacterEncoding("UTF-8");

        //验证码校验

        //获得页面输入的验证

        String checkCode_client = request.getParameter("checkCode");

        //获得生成图片的文字的验证码

        String checkCode_session = (String) request.getSession().getAttribute("checkcode_session");

        //比对页面的和生成图片的文字的验证码是否一致

        if(!checkCode_session.equals(checkCode_client)){

            //错误信息提示

            request.setAttribute("loginInfo", "您的验证码不正确");

            //跳回登录页面

            request.getRequestDispatcher("/login.jsp").forward(request, response);

            return;

        }

        //获得页面的用户名和密码进行数据库的校验

        //具体方法在前几篇文章中有详细

        //......

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doGet(request, response);

    }

}

注意验证码img的src属性是url-pattern种生成验证码的servlet

表单提交action是验证码校验的sevlet

码农公寓

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