数字验证码生成.docVIP

数字验证码生成 吧 例程7-11 check_code.html h3带有验证码的登录页面/h3 form action=servlet/LogonFormServlet method=post 用户名：input type=text name=namebr 密 码：input type=password name=passbr 验证码：input type=text name=check_code img src=servlet/CheckCodeServletbr input type=submit value=登录 /form 例程7-12 CheckCodeServlet.java 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