import java.io.*;

import javax.servlet.*;
import javax.servlet.http.*;
import java.util.Random;
import java.awt.*;
import java.awt.image.*;
import javax.imageio.*;
import javax.jms.Session;

public class SafeCode extends HttpServlet {
	//产生随即的字体
	private Font getFont() {
		Random random = new Random();
		Font font[] = new Font[5];
		font[0] = new Font("Ravie", Font.PLAIN, 24);
		font[1] = new Font("Antique Olive Compact", Font.PLAIN, 24);
		font[2] = new Font("Forte", Font.PLAIN, 24);
		font[3] = new Font("Wide Latin", Font.PLAIN, 24);
		font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, 24);
		return font[random.nextInt(5)];
	}

	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		// 设置响应头 Content-type类型
		resp.setContentType("image/jpeg");
		// 以下三句是用于设置页面不缓存
		resp.setHeader("Pragma", "No-cache");
		resp.setHeader("Cache-Control", "No-cache");
		resp.setDateHeader("Expires", 0);

		OutputStream os = resp.getOutputStream();
		int width = 83, height = 30;
		// 建立指定宽、高和BufferedImage对象
		BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);

		Graphics g = image.getGraphics(); // 该画笔画在image上
		Color c = g.getColor(); // 保存当前画笔的颜色，用完画笔后要回复现场
		g.fillRect(0, 0, width, height);
		

		char[] ch = "abcdefghjkmnpqrstuvwxyz23456789".toCharArray(); // 随即产生的字符串 不包括 i l(小写L) o（小写O） 1（数字1）0(数字0)
		int length = ch.length; // 随即字符串的长度
		String sRand = ""; // 保存随即产生的字符串
		Random random = new Random();
		for (int i = 0; i < 4; i++) {
			// 设置字体
			g.setFont(getFont());
			// 随即生成0-9的数字
			String rand = new Character(ch[random.nextInt(length)]).toString();
			sRand += rand;
			// 设置随机颜色
			g.setColor(new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)));
			g.drawString(rand, 20 * i + 6, 25);
		}
		//产生随即干扰点
		for (int i = 0; i < 20; i++) {
			int x1 = random.nextInt(width);
			int y1 = random.nextInt(height);
			g.drawOval(x1, y1, 2, 2);
		}
		g.setColor(c); // 将画笔的颜色再设置回去
		g.dispose();

		//将验证码记录到session
		req.getSession().setAttribute("safecode", sRand);
		// 输出图像到页面
		ImageIO.write(image, "JPEG", os);

	}

	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doGet(req, resp);
	}

}