jsp随机验证码（图片）

package com.vnvmall.goldfish.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.ServletConfig; 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 ValidateImage extends HttpServlet { public void init(ServletConfig conf) throws ServletException { super.init(conf); } public void doGet(HttpServletRequest req,HttpServletResponse res) throws ServletException, IOException { res.setContentType("image/jpeg"); res.setHeader("Pragma","No-cache"); res.setHeader("Cache-Control","no-cache"); res.setDateHeader("Expires", 0); HttpSession session = req.getSession(); // 在内存中创建图象 int width=60, height=20; 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(getRandColor(200,250)); g.fillRect(0, 0, width, height); // 设定字体 g.setFont(new Font("Times New Roman",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(getRandColor(160,200)); 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(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110))); // 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+6,16); } // 将认证码存入SESSION session.setAttribute("VerifyCode",sRand); // 图象生效 g.dispose(); // 输出图象到页面 ImageIO.write(image, "JPEG", res.getOutputStream()); //JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(res.getOutputStream()); //encoder.encode(image); } public void doPost(HttpServletRequest req,HttpServletResponse res) throws ServletException, IOException { doGet(req,res); } //给定范围获得随机颜色 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); } }