验证码--零起步[关于技术 ]
今天没什么事做,去CSDN上看了几页张孝祥的书,觉得不错,剖析的很不一样 看到验证码那点觉得很有意思于是小试一下,不过依然因为基础差被搞倒 在web.xml配置servlet时上折腾了很长时间才弄清楚那个路径怎么认到,结果还是放弃tomcat用熟悉的jboss 最后可算行了 产生随机数的方法贴出来如下(使用session实现,这也是验证码的基本要求) import java.io.*; import javax.servlet.*; import javax.servlet.http.*; import java.awt.*; import java.awt.image.*; import javax.imageio.ImageIO; public class CheckCodeServlet extends HttpServlet { private static int WIDTH = 60; private static int HEIGHT = 20; public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException { HttpSession session = request.getSession(); response.setContentType("image/jpeg"); ServletOutputStream sos = response.getOutputStream(); //设置浏览器不要缓存此图片 response.setHeader("Pragma","No-cache"); response.setHeader("Cache-Control","no-cache"); response.setDateHeader("Expires", 0); //创建内存图象并获得其图形上下文 BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics(); //产生随机的认证码 char [] rands = generateCheckCode(); //产生图像 drawBackground(g); drawRands(g,rands); //结束图像的绘制过程,完成图像 g.dispose(); //将图像输出到客户端 ByteArrayOutputStream bos = new ByteArrayOutputStream(); ImageIO.write(image, "JPEG", bos); byte [] buf = bos.toByteArray(); response.setContentLength(buf.length); //下面的语句也可写成:bos.writeTo(sos); sos.write(buf); bos.close(); sos.close(); //将当前验证码存入到Session中 session.setAttribute("check_code",new String(rands)); //直接使用下面的代码将有问题,Session对象必须在提交响应前获得 //request.getSession().setAttribute("check_code",new String(rands)); } private char [] generateCheckCode() { //定义验证码的字符表 String chars = "0123456789abcdefghijklmnopqrstuvwxyz"; char [] rands = new char[4]; for(int i=0; i<4; i++) { int rand = (int)(Math.random() * 36); rands[i] = chars.charAt(rand); } return rands; } private void drawRands(Graphics g , char [] rands) { g.setColor(Color.BLACK); g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18)); //在不同的高度上输出验证码的每个字符 g.drawString("" + rands[0],1,17); g.drawString("" + rands[1],16,15); g.drawString("" + rands[2],31,18); g.drawString("" + rands[3],46,16); System.out.println(rands); } private void drawBackground(Graphics g) { //画背景 g.setColor(new Color(0xDCDCDC)); g.fillRect(0, 0, WIDTH, HEIGHT); //随机产生120个干扰点 for(int i=0; i<120; i++) { int x = (int)(Math.random() * WIDTH); int y = (int)(Math.random() * HEIGHT); int red = (int)(Math.random() * 255); int green = (int)(Math.random() * 255); int blue = (int)(Math.random() * 255); g.setColor(new Color(red,green,blue)); g.drawOval(x,y,1,0); } } }
Posted by jacky.v.c at 2006/11/05 16:56:23 查看全文| 发表评论(0)| Trackback(0)| 编辑
so help me to get where i belong......i love u...forever....
|