Response生成注册验证码实现例子02
Servlet生成注册验证码图片CheckCodeServlet.java 示例2:
import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.ByteArrayOutputStream; import java.io.IOException; 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; import javax.servlet.http.HttpSession; @SuppressWarnings("serial") 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); } } }
2,注册页面: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="name"><br> 密 码:<input type="password" name="pass"><br> 验证码:<input type="text" name="check_code"> <img src="servlet/CheckCodeServlet"><br> <input type="submit" value="登录"> </form>
3,验证注册信息页面:LogonFormServlet.java
import java.io.*; import javax.servlet.*; import javax.servlet.http.*; @SuppressWarnings("serial") 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!"); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }