随机验证码
2010-08-25 16:26:14| 分类:
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package com.web;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class ImageServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
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
{
response.setContentType("image/jpeg");
HttpSession session = request.getSession();
int width = 60;
int height = 20;
//设置浏览器不要缓存此图片
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
//创建内存图像并获得其图形上下文
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
//产生随机验证码
//定义验证码的字符表
String chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
char[] rands = new char[4];
for(int i = 0; i < 4; i++) {
int rand = (int) (Math.random() * 36);
rands[i] = chars.charAt(rand);
}
//产生图像
//画背景
g.setColor(new Color(0xDCDCDC));
g.fillRect(0, 0, width, height);
// 随机产生120个干扰点
for(int i = 0; i < 120; i++) {
int x = (int)(Math.random() * width);
int y = (int)(Math.random() * height);
int red = (int)(Math.random() * 255);
int green = (int)(Math.random() * 255);
int blue = (int)(Math.random() * 255);
g.setColor(new Color(red, green, blue));
g.drawOval(x, y, 1, 0);
}
g.setColor(Color.BLACK);
g.setFont(new Font(null, Font.ITALIC|Font.BOLD, 18));
//在不同的高度上输出验证码的不同字符
g.drawString("" + rands[0], 1, 17);
g.drawString("" + rands[1], 16, 15);
g.drawString("" + rands[2], 31, 18);
g.drawString("" + rands[3], 46, 16);
g.dispose();
//将图像输出到客户端
ServletOutputStream sos = response.getOutputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ImageIO.write(image, "JPEG", baos);
byte[] buffer = baos.toByteArray();
response.setContentLength(buffer.length);
sos.write(buffer);
baos.close();
sos.close();
// 将验证码放到 session 中
session.setAttribute("checkCode", new String(rands));
}
}
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