验证码的生成

做web开发，很多时间需要大量生成难证码，写一个验证码是一件很容易的事，但是写得好不会是一件易事。

以下是我写的一个验证码生成方法，经改进行，性能比初时(我第一次写时)被时提升了40%以上，仅供参考。

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 该方法主要是生成验证码,并返4位回验证码
 * 
 * @author Jacky *
 */
public final class ImageCode {

	/**
	 * 经常用到的作静态常量处理，这样会加快处理速度，减少变量第次都要生成的内存空间浪费，用final使程序不用录找该类是否被继承，减少加载时间
	 * 
	 */

	private static final Random random = new Random();

	// 预定义定义四种字体，并将随机得到
	private static final Font[] CODEFONT = { new Font("宋体", Font.BOLD, 25), new Font("宋体", Font.BOLD, 25), new Font("宋体", Font.BOLD, 25),
			new Font("宋体", Font.BOLD, 25) };

	// 预定义定义字体颜色，并将随机得到色
	private static final Color[] FONTCOLOR = { Color.ORANGE, Color.RED, Color.PINK, Color.BLUE, Color.GREEN };

	// 预定义 图片的背景颜色，并将随机得到
	private static final Color[] BGCOLOR = { Color.BLACK, Color.WHITE };

	// 预定义干扰线的颜色
	private static final Color LINECOLOR = new Color(242, 234, 22);

	// 预定义生随机的字符，用数组取值比String类型取一个值快
	private static final String[] CODE = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "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" };

	// 返回的验证码
	private static StringBuffer CONDENUMBER = null;

	// 预定义图片大小
	private static final int WIDTH = 100, HEIGHT = 25;

	/**
	 * 生成验证码输出，并输出
	 * 
	 * @param request
	 * @param response
	 * @return codeNumber
	 */
	public final String image(HttpServletRequest request, HttpServletResponse response) {
		CONDENUMBER = new StringBuffer();
		BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
		Graphics g = image.getGraphics();
		g.setColor(BGCOLOR[random.nextInt(2)]);
		g.fillRect(0, 0, WIDTH, HEIGHT);
		for (int i = 0; i < 4; i++) {
			drawCode(g, i);
		}
		drawNoise(g, 8);
		g.setColor(Color.gray);
		g.drawRect(0, 0, WIDTH - 1, HEIGHT - 1);
		g.dispose();
		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);
		response.setContentType("image/png");
		ServletOutputStream sos = null;
		try {
			sos = response.getOutputStream();
			ImageIO.write(image, "png", sos);
			sos.flush();
			sos.close();
		} catch (Exception e) {
			e.printStackTrace();
			return null;
		}
		return CONDENUMBER.toString();
	}

	/**
	 * 画验证码
	 * 
	 * @param request
	 * @param response
	 * @return void
	 */
	private final void drawCode(Graphics graphics, int i) {
		String number = CODE[random.nextInt(36)];
		graphics.setFont(CODEFONT[random.nextInt(4)]);
		graphics.setColor(FONTCOLOR[random.nextInt(5)]);
		graphics.drawString(number, 10 + i * 20, 20);
		CONDENUMBER.append(number);
	}

	/**
	 * 画干扰线
	 * 
	 * @param graphics
	 * @param void
	 */
	private final void drawNoise(Graphics graphics, int lineNumber) {
		graphics.setColor(LINECOLOR);
		int pointX1, pointY1, pointX2, pointY2;
		for (int i = 0; i < lineNumber; i++) {
			pointX1 = 1 + (int) (Math.random() * WIDTH);
			pointY1 = 1 + (int) (Math.random() * HEIGHT);
			pointX2 = 1 + (int) (Math.random() * WIDTH);
			pointY2 = 1 + (int) (Math.random() * HEIGHT);
			graphics.drawLine(pointX1, pointY1, pointX2, pointY2);
		}
	}

}

一个调用的例子：

public void image(HttpServletRequest request, HttpServletResponse response) {
		ImageCode ic = new ImageCode();
		String imageCode = ic.image(request, response);
		request.getSession().removeAttribute("imageCode");
                  //转为小写，从页面输入也转为小写，以达到不分大小写作用
		request.getSession().setAttribute("imageCode", imageCode.toLowerCase());
	}

不知觉位对上面的写法有什么建议，谢谢。

评论

4 楼 wuhui 2008-07-12  

还可以，可以学习一下

3 楼 xiyeqing99 2008-07-10  

ding up

2 楼 chenlb 2008-07-10  

依赖Servlet api...

1 楼 yanbingwei 2008-07-09  

还不错.