局部刷新验证码

局部刷新验证码 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.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ImageAction extends HttpServlet { /** * 执行登陆的业务处理 * @param request:发送上来的请求 * @return destJsp:目标URL */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException,ServletException{ //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 = 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(220, 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.drawRect(0,0,width-1,height-1); g.draw3DRect(0,0,width-1,height-1,true); //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(6位数字) String sRand = ""; String s = "012345678901234567890123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ01 2345678901234567890123456789abcdefghijklmnopqrstuvwxyz"; for (int i = 0; i < 4; i++) { char rand =s.charAt(random.nextInt(s.length())); 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(String.valueOf(rand), 13 * i + 6, 16); } g.drawOval(0,12,60,11); // 将认证码存入SESSION request.getSession().setAttribute("rand", sRand); // 图象生效 g.dispose(); ServletOutputStream output; try { output = response.getOutputStream(); // 输出图象到页面 ImageIO.write(image, "JPEG", output); } catch (IOException e) { e.printStackTrace(); } } /** * 生成随机颜色 */ 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); } } ImageAction cn.netjava.servlet.ImageAction ImageAction /ImageAction function checkcode(){ document.getElementById("code").src = "ImageAction";// 改变验证码图片 } //因为是单一功能测试，所以页面比较简单 //只有一个验证码的图片和一行字........
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