java生成验证图片
========================jsp==============================

=====================web.xml=================
package com.e8online2.comm.util;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;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;public class IdentifyingServlet extends HttpServlet {/** *  */private static final long serialVersionUID = 1L;protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {response.setContentType("image/jpeg");// 给定范围获得随机颜色// 设置页面不缓存response.setHeader("Pragma", "No-cache");response.setHeader("Cache-Control", "no-cache");response.setDateHeader("Expires", 0);// 在内存中创建图象int width = 60, height = 17;BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);// 获取图形上下文Graphics g = image.getGraphics();// 生成随机类Random random = new Random();// 设定背景色g.setColor(getRandom(254, 255));g.fillRect(0, 0, width, height);// 设定字体g.setFont(new Font("Cooper Black", Font.PLAIN, 18));// 画边框// g.setColor(new Color());// g.drawRect(0,0,width-1,height-1);// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到g.setColor(getRandom(230, 240));for (int i = 0; i < 155; i++) {int x = random.nextInt(width);int y = random.nextInt(height);int xl = random.nextInt(12);int yl = random.nextInt(12);g.drawLine(x, y, x + xl, y + yl);}// 取随机产生的认证码(4位数字)String sRand = "";for (int i = 0; i < 4; i++) {String rand = String.valueOf(random.nextInt(10));sRand += rand;// 将认证码显示到图象中g.setColor(new Color(100 + random.nextInt(130), 100 + random.nextInt(130), 100 + random.nextInt(130)));// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成g.drawString(rand, 13 * i + 6, 14);}// 将认证码存入SESSIONrequest.getSession().setAttribute("IdentifyingCode", sRand);// 图象生效g.dispose();// 输出图象到页面ImageIO.write(image, "JPEG", response.getOutputStream());}private Color getRandom(int mixValue, int maxValue) {Random random = new Random();if (mixValue > 255)mixValue = 255;if (maxValue > 255)maxValue = 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);int rgb = mixValue + random.nextInt(maxValue - mixValue);return new Color(rgb, rgb, rgb);}}