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：
时间： 2024-10-13 01:53:55