java验证码的用法

1、验证码1. 在项目中添加AuthImg.java（Servlet）2. 在web.xml中配置该ServletAuthImgorg.agency.servlet.AuthImgAuthImg/authImg.jpg3. 页面引用/验证码function changeImg()document.getElementById(authImg).src =authImg.jpg?timpstamp= + new Date().getTime();验证码:4. 得到验证码！在AuthImg中它把验证码封装到了session对象中名字是rand然后得到code和session中的rand比较这样验证码的

2、功能就完成了！AuthImg.javapackage org.agency.servlet;import javax.servlet.*;import javax.servlet.http.*;import java.io.*;import java.awt.*;import java.awt.image.*;import java.util.*;import javax.imageio.*;/* * 图形验证码 hzl 09-11-29 */public class AuthImg extends HttpServlet private static final long serialVer

3、sionUID = 1L;/ 定义图形验证码中绘制字符的字体private final Font mFont = new Font(Arial Black, Font.PLAIN, 16);/ 定义图形验证码的大小private final int IMG_WIDTH = 100;private final int IMG_HEIGTH = 20;/ 定义一个获取随机颜色的方法private Color getRandColor(int fc, int bc) Random random = new Random();if (fc 255)fc = 255;if (bc 255)bc = 25

4、5;int r = fc + random.nextInt(bc - fc);int g = fc + random.nextInt(bc - fc);int b = fc + random.nextInt(bc - fc);/ 得到随机颜色return new Color(r, g, b);/ 重写service方法，生成对客户端的响应public void service(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException / 设置禁止缓存response

5、.setHeader(Pragma, No-cache);response.setHeader(Cache-Control, no-cache);response.setDateHeader(Expires, 0);response.setContentType(image/jpeg);BufferedImage image = new BufferedImage(IMG_WIDTH, IMG_HEIGTH,BufferedImage.TYPE_INT_RGB);Graphics g = image.getGraphics();Random random = new Random();g.se

6、tColor(getRandColor(200, 250);/ 填充背景色g.fillRect(1, 1, IMG_WIDTH - 1, IMG_HEIGTH - 1);/ 为图形验证码绘制边框g.setColor(new Color(102, 102, 102);g.drawRect(0, 0, IMG_WIDTH - 1, IMG_HEIGTH - 1);g.setColor(getRandColor(160, 200);/ 生成随机干扰线for (int i = 0; i 80; i+) int x = random.nextInt(IMG_WIDTH - 1);int y = rand

7、om.nextInt(IMG_HEIGTH - 1);int xl = random.nextInt(6) + 1;int yl = random.nextInt(12) + 1;g.drawLine(x, y, x + xl, y + yl);g.setColor(getRandColor(160, 200);/ 生成随机干扰线for (int i = 0; i 80; i+) int x = random.nextInt(IMG_WIDTH - 1);int y = random.nextInt(IMG_HEIGTH - 1);int xl = random.nextInt(12) + 1

8、;int yl = random.nextInt(6) + 1;g.drawLine(x, y, x - xl, y - yl);/ 设置绘制字符的字体g.setFont(mFont);/ 用于保存系统生成的随机字符串String sRand = ;for (int i = 0; i 6; i+) String tmp = getRandomChar();sRand += tmp;/ 获取随机颜色g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110);/

9、在图片上绘制系统生成的随机字符g.drawString(tmp, 15 * i + 10, 15);/ 获取HttpSesssion对象HttpSession session = request.getSession(true);/ 将随机字符串放入HttpSesssion对象中session.setAttribute(rand, sRand);g.dispose();/ 向输出流中输出图片ImageIO.write(image, JPEG, response.getOutputStream();/ 定义获取随机字符串方法private String getRandomChar() / 生成一个0、1、2的随机数字int rand = (int) Math.round(Math.random() * 2);long itmp = 0;char ctmp = u0000;switch (rand) / 生成大写字母case 1:itmp = Math.round(Math.random() * 25 + 65);ctmp = (char) itmp;return String.valueOf(ctmp);/ 生成小写字母case 2:it