使用Servlet创建验证码图片

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在做用户登录的时候，为了安全起见，都会在登录按钮前设置一个验证码输入，下面是一个验证码输入的函数，用servlet开发的。

package com.wy.servlet;import java.awt.*;import java.awt.image.BufferedImage;import java.io.IOException;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;import javax.servlet.http.HttpSession;public class PictureCheckCode extends HttpServlet {    private Font mFont = new Font("黑体", Font.BOLD, 17);    public PictureCheckCode() {        super();    }    public void destroy() {        super.destroy(); // Just puts "destroy" string in log        // Put your code here    }    public void init() throws ServletException {        // Put your code here        super.init();    }    Color getRandColor(int fc, int bc) {        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);    }    public void service(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        response.setHeader("Pragma", "No-cache");        response.setHeader("Cache-Control", "No-cache");        response.setDateHeader("Expires", 0);        // 指定生成的响应是图片        response.setContentType("image/jpeg");        int width = 70;        int height = 19;        BufferedImage image = new BufferedImage(width, height,                BufferedImage.TYPE_INT_RGB);        Graphics g = image.getGraphics();        Random random = new Random();        g.setColor(getRandColor(200, 250));        g.fillRect(1, 1, width - 1, height - 1);        g.setColor(new Color(102, 102, 102));        g.drawRect(0, 0, width - 1, height - 1);        g.setFont(mFont);        g.setColor(getRandColor(160, 200));        // 画随机的线条        for (int i = 0; i < 155; i++) {            int x = random.nextInt(width - 1);            int y = random.nextInt(height - 1);            int x1 = random.nextInt(6) + 1;            int y1 = random.nextInt(12) + 1;            g.drawLine(x, y, x + x1, y + y1);        }        String sRand = "";        // 输出随机的验证文字        for (int i = 0; i < 4; i++) {            int itmp = random.nextInt(26) + 65;            char ctmp = (char) itmp;            sRand += String.valueOf(ctmp);            g.setColor(new Color(20 + random.nextInt(110), 20 + random                    .nextInt(110), 20 + random.nextInt(110)));            g.drawString(String.valueOf(ctmp), 15 * i + 10, 16);        }        // 将生成的验证码保存到Session中        HttpSession session = request.getSession(true);        session.setAttribute("rand", sRand);        g.dispose();        ImageIO.write(image, "JPEG", response.getOutputStream());    }}

另外，需要在web.xml中进行配置，配置如下：

  <servlet>    <servlet-name>PictureCheckCode</servlet-name>    <servlet-class>com.wy.servlet.PictureCheckCode</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>PictureCheckCode</servlet-name>    <url-pattern>/PictureCheckCode</url-pattern>  </servlet-mapping>

然后，就可以在网页中使用了，使用方法如下：

<%@ page language="java" contentType="text/html; charset=utf-8"    pageEncoding="utf-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>验证码图片</title></head><body>    <div align="center">        <form action="userInfo?method=5" method="post">            <table width="367" border="0">                  <tr>                    <td><img border=0 src="PictureCheckCode" name="checkCode"></td>                    <td width="163" colspan="2"><input name="code" type="text"></td>                  </tr>                  <tr>                    <td height="25">&nbsp;</td>                    <td><input type="submit" name="Submit" value=" 提 交  "></td>                  </tr>                   <tr>                <td height="30">&nbsp;</td>                <td colspan="3">${requestScope.information}</td>            </tr>                </table>        </form>    </div></body></html>

生成的效果如下：
这里写图片描述

验证方法如下：

    private void checkPictureCode(HttpServletRequest request,            HttpServletResponse response) throws UnsupportedEncodingException,            ServletException, IOException {        String information="";        session = request.getSession();        String rand = (String) session.getAttribute("rand");        String code = (String) request.getParameter("code");            if (rand.equals(code)) {                information = "你输入的验证码正确";            } else {                information = "您输入的验证码不正确！";            }        request.setAttribute("information", information);        request.getRequestDispatcher("checkPictureCode.jsp").forward(request, response);    }

大致的流程就是这些。

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