servlet验证码

web.xml

<servlet>
	<servlet-name>ValidationCodeServlet</servlet-name>
	<servlet-class>org.yingzhuo.servlet.ValidationCodeServlet</servlet-class>
</servlet>

<servlet-mapping>
	<servlet-name>ValidationCodeServlet</servlet-name>
	<url-pattern>/validationcode.jpg</url-pattern>
</servlet-mapping>

package org.yingzhuo.servlet;

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 ValidationCodeServlet extends HttpServlet {

	private static final long serialVersionUID = -5500460293981359815L;

	private static final String CONTENT_TYPE = "image/jpeg";

	// 设置字母的大小,大小
	private Font mFont = new Font("Times New Roman", Font.PLAIN, 17);

	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);
	}

	@Override
	protected void service(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {

		response.setHeader("Pragma", "No-cache");
		response.setHeader("Cache-Control", "no-cache");
		response.setDateHeader("Expires", 0);
		// 表明生成的响应是图片
		response.setContentType(CONTENT_TYPE);

		int width = 100, height = 18;
		BufferedImage image = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);

		Graphics g = image.getGraphics();
		Random random = new Random();
		g.setColor(getRandColor(200, 250));
		g.fillRect(1, 1, width - 1, height - 1);
		g.setColor(new Color(102, 102, 102));
		g.drawRect(0, 0, width - 1, height - 1);
		g.setFont(mFont);

		g.setColor(getRandColor(160, 200));

		// 画随机线
		for (int i = 0; i < 155; i++) {
			int x = random.nextInt(width - 1);
			int y = random.nextInt(height - 1);
			int xl = random.nextInt(6) + 1;
			int yl = random.nextInt(12) + 1;
			g.drawLine(x, y, x + xl, y + yl);
		}

		// 从另一方向画随机线
		for (int i = 0; i < 70; i++) {
			int x = random.nextInt(width - 1);
			int y = random.nextInt(height - 1);
			int xl = random.nextInt(12) + 1;
			int yl = random.nextInt(6) + 1;
			g.drawLine(x, y, x - xl, y - yl);
		}

		// 生成随机数,并将随机数字转换为字母
		String sRand = "";
		for (int i = 0; i < 6; i++) {
			int itmp = random.nextInt(26) + 65;
			char ctmp = (char) itmp;
			sRand += String.valueOf(ctmp);
			g.setColor(new Color(20 + random.nextInt(110), 20 + random
					.nextInt(110), 20 + random.nextInt(110)));
			g.drawString(String.valueOf(ctmp), 15 * i + 10, 16);
		}

		HttpSession session = request.getSession(true);
		session.setAttribute("rand", sRand);
		g.dispose();
		ImageIO.write(image, "JPEG", response.getOutputStream());
	}
}

部署以后访问http://localhost:8080/validation/validationcode.jpg即可看到效果


jsp页面展示图片也很简单

<img id="img" src="validationcode.jpg" /> <a id="a" style="cursor: pointer;">换一个</a>

可以通过javascript(jquery)来变换图片

$(function(){
	$("#a").bind("click", function() {
		$("#img").attr("src", "validationcode.jpg?time=" + new Date());
	});
});