java验证码实例

1.servlet, ImageServlet.java

package com.bc.servlet;import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class ImageServlet extends HttpServlet {       public void doGet(HttpServletRequest request, HttpServletResponse response)                     throws ServletException, IOException {              this.doPost(request, response);       }       // 生成数字和字母的验证码       public void doPost(HttpServletRequest request, HttpServletResponse response)                     throws ServletException, IOException {              BufferedImage img = new BufferedImage(68, 22,                            BufferedImage.TYPE_INT_RGB);              // 得到该图片的绘图对象              Graphics g = img.getGraphics();              Random r = new Random();              Color c = new Color(200, 150, 255);              g.setColor(c);              // 填充整个图片的颜色              g.fillRect(0, 0, 68, 22);              // 向图片中输出数字和字母              StringBuffer sb = new StringBuffer();              char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toCharArray();              int index, len = ch.length;              for (int i = 0; i < 4; i ++) {                     index = r.nextInt(len);                     g.setColor(new Color(r.nextInt(88), r.nextInt(188), r.nextInt(255)));                     g.setFont(new Font("Arial", Font.BOLD | Font.ITALIC, 22));// 输出的字体和大小                                      g.drawString("" + ch[index], (i * 15) + 3, 18);//写什么数字，在图片的什么位置画                     sb.append(ch[index]);              }              request.getSession().setAttribute("piccode", sb.toString());              ImageIO.write(img, "JPG", response.getOutputStream());       }    }

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2.web.xml配置servlet

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<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://java.sun.com/xml/ns/javaee?

http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

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<servlet>??<servlet-name>ImageServlet</servlet-name>??<servlet-class>com.bc.servlet.ImageServlet</servlet-class></servlet>
<servlet-mapping> ?<servlet-name>ImageServlet</servlet-name> ?<url-pattern>/servlet/ImageServlet</url-pattern></servlet-mapping>
</web-app>

3.AdminLogin.jsp调用

<script language="javascript" > // 重载验证码    function reloadVerifyCode(){               var timenow = new Date().getTime();                                  document.getElementById("safecode").src="<%=request.getContextPath()%>/servlet/ImageServlet?d="+timenow;    } </script><td> <img alt="java验证码范例" id="safecode" src="<%=request.getContextPath()%>/servlet/ImageServlet"/>              <a href="javascript:reloadVerifyCode();"><br/>看不清楚,换一个</a>              </td>

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