java servlet 实现验证码
servlet 代码：
import java.io.*;import javax.servlet.*;import javax.servlet.http.*;import java.util.Random;import java.awt.*;import java.awt.image.*;import javax.imageio.*;import javax.jms.Session;public class SafeCode extends HttpServlet {//产生随即的字体private Font getFont() {Random random = new Random();Font font[] = new Font[5];font[0] = new Font("Ravie", Font.PLAIN, 24);font[1] = new Font("Antique Olive Compact", Font.PLAIN, 24);font[2] = new Font("Forte", Font.PLAIN, 24);font[3] = new Font("Wide Latin", Font.PLAIN, 24);font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, 24);return font[random.nextInt(5)];}protected void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {// 设置响应头 Content-type类型resp.setContentType("image/jpeg");// 以下三句是用于设置页面不缓存resp.setHeader("Pragma", "No-cache");resp.setHeader("Cache-Control", "No-cache");resp.setDateHeader("Expires", 0);OutputStream os = resp.getOutputStream();int width = 83, height = 30;// 建立指定宽、高和BufferedImage对象BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);Graphics g = image.getGraphics(); // 该画笔画在image上Color c = g.getColor(); // 保存当前画笔的颜色，用完画笔后要回复现场g.fillRect(0, 0, width, height);char[] ch = "abcdefghjkmnpqrstuvwxyz23456789".toCharArray(); // 随即产生的字符串 不包括 i l(小写L) o（小写O） 1（数字1）0(数字0)int length = ch.length; // 随即字符串的长度String sRand = ""; // 保存随即产生的字符串Random random = new Random();for (int i = 0; i < 4; i++) {// 设置字体g.setFont(getFont());// 随即生成0-9的数字String rand = new Character(ch[random.nextInt(length)]).toString();sRand += rand;// 设置随机颜色g.setColor(new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)));g.drawString(rand, 20 * i + 6, 25);}//产生随即干扰点for (int i = 0; i < 20; i++) {int x1 = random.nextInt(width);int y1 = random.nextInt(height);g.drawOval(x1, y1, 2, 2);}g.setColor(c); // 将画笔的颜色再设置回去g.dispose();//将验证码记录到sessionreq.getSession().setAttribute("safecode", sRand);// 输出图像到页面ImageIO.write(image, "JPEG", os);}protected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {doGet(req, resp);}}?xml 代码：
<servlet><servlet-name>code</servlet-name><servlet-class>SafeCode</servlet-class></servlet><servlet-mapping><servlet-name>code</servlet-name><url-pattern>/servlet/safecode</url-pattern></servlet-mapping>?
jsp代码：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" %><%String action = request.getParameter("action");String safecodeText = request.getParameter("safecodeTest");if("action".equals(action)){String safecode = (String)session.getAttribute("safecode");if(safecode.equals(safecodeText)){out.print("验证码正确！");}else{out.print("验证码错误！请重新输入！");}}%><html> <head> <title>验证码测试</title> </head> <body> <form action="index.jsp" method="post"> <input type="hidden" name="action" value="action"/> <img alt="java servlet 兑现验证码" src="servlet/safecode"> <input type="text" name="safecodeTest"> <input type="submit" value="go"> </form> </body></html>?