java Servlet产生验证码图片

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书写验证码产生程序：package com.bobo.shopping.common.util;/** *

Title:用于产生校验码的servlet类

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Description:用于产生校验码的servlet类

 * @version 1.0 */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 CheckCodeServlet extends HttpServlet {   private static final long serialVersionUID = 1L;     private static int codeLength = 4; //验证码位数    private static int imageWidth = 60; //图片宽度   private static int imageHeight = 20; //图片高度    public void doGet(HttpServletRequest request, HttpServletResponse response)     throws ServletException, IOException {          //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        BufferedImage image = new BufferedImage(imageWidth, imageHeight, 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(getRandColor(200, 250));       g.fillRect(0, 0, imageWidth, imageHeight);       //设定字体       g.setFont(new Font('Times New Roman', Font.PLAIN, 18));        //画边框        g.setColor(new Color(20,20,20));       g.drawRect(0, 0, imageWidth - 1, imageHeight - 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(getRandColor(160, 200));     for (int i = 0; i < 155; i++) {           int x = random.nextInt(imageWidth);           int y = random.nextInt(imageHeight);           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     // 可以自己设置数字字母等，本例只是产生数字    String sRand = '';     for (int i = 0;i < codeLength; i++) {        String rand = String.valueOf(random.nextInt(10));        sRand += rand;        // 将认证码显示到图象中         // 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.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));         g.drawString(rand, 13 * i + 6, 16);     }     // 将认证码存入SESSION中     // 获取方式  request.getSession().getAttribute('checkCode');   request.getSession().setAttribute('checkCode', sRand);      // 图象生效    g.dispose();      // 输出图象到页面     ImageIO.write(image, 'JPEG', response.getOutputStream()); }   /**   * 获取随机颜色  * @param fc  * @param bc   * @return   */  private 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); }}