javascript实现验证码

henujava 2009-12-04 05:23:10

平时的登录验证码怎么实现的呢，是通过java的ＡＰＰＬＥＴ程序实现的吗？

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henujava 2009-12-06

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呵呵！谢啦！

singlion 2009-12-05

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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;

import javax.servlet.http.HttpSession;



public class ImageVerifier extends HttpServlet {

	private static final long serialVersionUID = 663333838518622898L;

	//验证码图像的大小，最小50*20，建议保持比例

	private static final int width = 100, height = 40;

	private static final String allchar = "23456789" +

			""+

			"AaBbCcDdEeFfGgHhJjKkMmNnPpQqRrSsTtUuVvWwXxYyZz";

	//0123456789

	//AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz

	public Color getRandColor(int fc, int bc) {

		Random random = new Random();

		if (fc > 255)

			fc = 255;

		if (bc > 255)

			bc = 255;

		int r = fc + random.nextInt(bc - fc);

		int g = fc + random.nextInt(bc - fc);

		int b = fc + random.nextInt(bc - fc);

		return new Color(r, g, b);



	}



	public void service(HttpServletRequest req, HttpServletResponse rep)

	throws IOException, ServletException {

		// 设置页面不缓存

		rep.setHeader("Pragma", "No-cache");

		rep.setHeader("Cache-Control", "no-cache");

		rep.setDateHeader("Expires", 0);

		rep.setContentType("image/jpeg");

		// 在内存中创建图象

		BufferedImage image = new BufferedImage(width, height,

				BufferedImage.TYPE_INT_RGB);

		// 获取图形上下文

		Graphics g = image.getGraphics();

		// 生成随机类

		Random random = new Random();

		// 设定背景色

		g.setColor(getRandColor(200, 250));

		g.fillRect(0, 0, width, height);

		// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到

		for (int i = 0; i < 50; i++) {

			g.setColor(getRandColor(100, 200));

			int x = random.nextInt(width);

			int y = random.nextInt(height);

			int xl = random.nextInt(width);

			int yl = random.nextInt(height);

			g.drawLine(x, y, x + xl, y + yl);

		}

		// 取随机产生的认证码(4位数字)

		String sRand = "";

		for (int i = 0; i < 4; i++) {

			String rand = "" + allchar.charAt(random.nextInt(allchar.length()));

			sRand += rand;

			// 将认证码显示到图象中

			g.setColor(new Color(random.nextInt(200), random

					.nextInt(200), random.nextInt(200)));// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成

			g.setFont(new Font("dd", Font.PLAIN, new Random().nextInt(height/2) + 16));

			g.drawString(rand, (width*11/50) * i + (width*6/50), 

					new Random().nextInt(height/2) + height/2);

		}

		// 将认证码存入SESSION

		HttpSession session = req.getSession();

		session.setAttribute("verify", sRand);

		// 图象生效

		g.dispose();

		// 输出图象到页面

		ImageIO.write(image, "JPEG", rep.getOutputStream());

	}

}