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锁定老帖子 主题：用servlet进行图片验证
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发表时间：2008-03-25
<pre name="code" class="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); } } }</pre> <pre name="code" class="java"> import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class LogonFormServlet extends HttpServlet { public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=GB2312"); PrintWriter out = response.getWriter(); HttpSession session = request.getSession(false); if(session == null) { out.println("验证码处理问题!"); return; } String savedCode = (String)session.getAttribute("check_code"); if(savedCode == null) { out.println("验证码处理问题!"); return; } String checkCode = request.getParameter("check_code"); if(!savedCode.equals(checkCode)) { /*验证码未通过，不从Session中清除原来的验证码， 以便用户可以后退回登录页面继续使用原来的验证码进行登录*/ out.println("验证码无效!"); return; } /*验证码检查通过后，从Session中清除原来的验证码， 以防用户后退回登录页面继续使用原来的验证码进行登录*/ session.removeAttribute("check_code"); out.println("验证码通过，服务器正在校验用户名和密码!"); } } </pre> </pre><pre name="code" class="java"><servlet> <servlet-name>CheckCodeServlet</servlet-name> <servlet-class>CheckCodeServlet</servlet-class> </servlet> <servlet> <servlet-name>LogonFormServlet</servlet-name> <servlet-class>LogonFormServlet</servlet-class> </servlet> …… <servlet-mapping> <servlet-name>CheckCodeServlet</servlet-name> <url-pattern>/servlet/CheckCodeServlet</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>LogonFormServlet</servlet-name> <url-pattern>/servlet/LogonFormServlet</url-pattern> </servlet-mapping> </pre> 声明：ITeye文章版权属于作者，受法律保护。没有作者书面许可不得转载。
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