一个产生验证码的Servlet

package org.newboy.servlet; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; import java.util.*; import java.awt.image.*; import java.awt.*; import com.sun.image.codec.jpeg.*; /** * @author liubo 夜光寒 * @version 1.0 * @since 2007-04-XX * * 在Web.xml中布署： <servlet> <servlet-name>CodePicServlet</servlet-name> <servlet-class>org.newboy.servlet.CodePicServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CodePicServlet</servlet-name> <url-pattern>/verifycode</url-pattern> </servlet-mapping> * * 在JSP中写上： * <img alt="验证码" src="/模块名/verifycode" mce_src="模块名/verifycode" /> * * 在调用时，运行String random = (String) session.getAttribute("verifyCode"); * 得到产生的验证码 * */ public class CodePicServlet extends HttpServlet { //改成Servlet，就重写service方法就不会出现IllegalStateException异常了，不要写在JSP中 protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String chose = "0123456789"; //abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ Random rand = new Random(); HttpSession session = request.getSession(true); //设置显示内容 response.setContentType("image/jpeg"); //设置页面不缓存 response.addHeader("pragma", "NO-cache"); response.addHeader("Cache-Control", "no-cache"); response.addDateHeader("Expries", 0); // 在内存中创建图象 int width = 65, height = 20; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); // 获取图形上下文 Graphics g = image.getGraphics(); //以下填充背景颜色 g.setColor(new Color(51, 102, 255)); g.fillRect(0, 0, width, height); //画边框 // g.setColor(Color.BLACK); // g.drawRect(0, 0, width - 1, height - 1); // 随机产生很多条干扰线，使图象中的认证码不易被其它程序探测到 for (int i = 0; i < 30; i++) { g.setColor(getRandColor(100, 150)); int x = rand.nextInt(width); int y = rand.nextInt(height); int xl = rand.nextInt(10); int yl = rand.nextInt(10); g.drawLine(x, y, x + xl, y + yl); } //设置字体 g.setFont(new Font("Times New Roman", Font.BOLD + Font.ITALIC, 16)); //设置字体颜色 g.setColor(Color.WHITE); // 取随机产生的认证码(4位数字) String sRand = ""; for (int i = 0; i < 4; i++) { String ranChar = String.valueOf(chose.charAt(rand.nextInt(chose.length()))); sRand += ranChar; //画一个出来 g.drawString(ranChar, 14 * i + 6, 15); } //在session中会有一个代码的对象 session.setAttribute("verifyCode", String.valueOf(sRand)); // 图象生效 g.dispose(); ServletOutputStream outStream = response.getOutputStream(); //将输出流建立成一个JPEG的文件编码 JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(outStream); encoder.encode(image); outStream.flush(); outStream.close(); } //给定范围获得随机颜色 Color getRandColor(int beginColor, int endColor) { Random random = new Random(); if (beginColor > 255) { beginColor = 255; } if (endColor > 255) { endColor = 255; } int r = beginColor + random.nextInt(endColor - beginColor); int g = beginColor + random.nextInt(endColor - beginColor); int b = beginColor + random.nextInt(endColor - beginColor); return new Color(r, g, b); } }