本例使用一个JavaBean，名为Image.java，包com.zempty.bean下;
三个JSP文件，分别为image.jsp、login.jsp、check.jsp。其中login.jsp是登录页，image.jsp用来调用JavaBean显示图片，check.jsp用来检测输入的验证码是否正确。
Image.java代码如下：
package com.zempty.bean; import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.IOException; import java.io.OutputStream; import java.util.Random; import javax.imageio.ImageIO; public class Image { // 验证码图片中可以出现的字符集，可根据需要修改 private char mapTable[] = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' }; /** * 功能：生成彩色验证码图片 参数width为生成图片的宽度，参数height为生成图片的高度，参数os为页面的输出流 */ public String getCertPic(int width, int height, OutputStream os) { if (width <= 0) width = 60; if (height <= 0) height = 20; BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); // 获取图形上下文 Graphics g = image.getGraphics(); // 设定背景色 g.setColor(new Color(0xDCDCDC)); g.fillRect(0, 0, width, height); // 画边框 g.setColor(Color.BLACK); g.drawRect(0, 0, width - 1, height - 1); // 取随机产生的认证码 String strEnsure = ""; for (int i = 0; i < 4; ++i) { strEnsure += mapTable[(int) (mapTable.length * Math.random())]; } // 将认证码显示到图像中，如果要生成更多位的验证码，增加drawString语句 g.setColor(Color.BLACK); g.setFont(new Font("Atlantic Inline", Font.PLAIN, 18)); String str = strEnsure.substring(0, 1); g.drawString(str, 8, 17); str = strEnsure.substring(1, 2); g.drawString(str, 20, 15); str = strEnsure.substring(2, 3); g.drawString(str, 35, 18); str = strEnsure.substring(3, 4); g.drawString(str, 45, 15); // 随机产生10个干扰点 Random rand = new Random(); for (int i = 0; i < 10; i++) { int x = rand.nextInt(width); int y = rand.nextInt(height); g.drawOval(x, y, 1, 1); } // 释放图形上下文 g.dispose(); try { // 输出图像到页面 ImageIO.write(image, "JPEG", os); } catch (IOException e) { System.out.println(e.getMessage()); return ""; } return strEnsure; } }
image.jsp代码如下：
<%--注意：contentType为image/jpeg--%>
<%@ page contentType="image/jpeg" pageEncoding="UTF-8"%> <jsp:useBean id="image" class="com.zempty.bean.Image" scope="session" /> <% String str = image.getCertPic(0, 0, response.getOutputStream()); //将验证码存入session session.setAttribute("certCode", str); out.clear(); //这句和下面那句要加上，否则会出现getOutputStream() has already been called for this response的错误。 out = pageContext.pushBody(); %>
login.jsp代码如下：
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>登录页面</title> </head> <body> <form name="form1" action="check.jsp" method="post"> 用户名：<input type="text" name="username" /> <br /> 密 码：<input type="password" name="password" /> <br /> 验证码：<input type="text" name="certCode" /><img src="image.jsp" /> <br /> <input type="submit" value="确定" /> </form> </body> </html>
check.jsp代码如下：
<%@ page pageEncoding="UTF-8"%> <% String certCode = request.getParameter("certCode"); if (certCode.equals((String) session.getAttribute("certCode"))) { out.print("验证码输入正确！"); } else { out.print("验证码输入错误！"); } %>
演示界面如下：
