Servlet验证码

package com.baiyang.lc.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.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

/**
 * 验证码
 */
public class VerifyCodeServlet extends HttpServlet {
	private final Logger logger = Logger.getLogger(VerifyCodeServlet.class);
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#HttpServlet()
	 */
	public VerifyCodeServlet() {
		super();
	}

	private 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);
		int width = 76, height = 34;
		BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);// 对访问的图片色调为RGB格式
		Graphics g = image.getGraphics();
		Random random = new Random();
		g.setColor(getRandColor(200, 250));
		g.fillRect(0, 0, width, height);
		g.setFont(new Font("Times New Roman", Font.ROMAN_BASELINE, 25));
		g.setColor(getRandColor(160, 200));
		int lineNum = 0;
		while (lineNum < 100) {
			lineNum = random.nextInt(200);
		}
		for (int i = 0; i < lineNum; i++) {
			int x = random.nextInt(width);
			int y = random.nextInt(height);
			int xl = random.nextInt(12);
			int yl = random.nextInt(12);
			g.drawLine(x, y, x + xl, y + yl);
		}
		String sRand = "";
		String chars = "1234567890QWERTYUIPLKJHGFDSAZXCVBNMqwertyuioplkjhgfdsazxcvbnm";
		for (int i = 0; i < 5; i++) {
			String rand = chars.charAt(random.nextInt(chars.length())) + "";
			sRand += rand;
			g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
			g.drawString(rand, 13 * i + 5, 24);
		}
		request.getSession().setAttribute("verifyCode", sRand);
		logger.debug("验证码：" + sRand);
		g.dispose();
		JPEGImageEncoder encode = JPEGCodec.createJPEGEncoder(response.getOutputStream());
		encode.encode(image);
	}
}