validcodeimggen.java

Servlet习题课 系统名称：登录及识别身份的下载

package com.mypack;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
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;

public class ValidCodeImgGen extends HttpServlet {

	public ValidCodeImgGen() {
		super();
	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		response.setHeader("Cache-Control", "no-cache");
		response.setHeader("Pragma", "no-cache");
		response.setDateHeader("Expires", 0);

		BufferedImage img = new BufferedImage(60, 20,
				BufferedImage.TYPE_INT_RGB);
		Graphics g = img.getGraphics();
		g.setColor(Color.WHITE);
		g.fillRect(0, 0, 60, 20);
		Random rand = new Random();
		String strRand = "";
		for (int i = 0; i < 4; i++) {
			int num = rand.nextInt(10);
			g.setFont(new Font("Arial", Font.BOLD, 16));
			g.setColor(new Color(rand.nextInt(128), rand.nextInt(128), rand
					.nextInt(128)));
			g.drawString(String.valueOf(num), i * 13 + 6, 16);
			strRand += num;
		}
		for (int i = 0; i < 200; i++) {
			g.setColor(new Color(rand.nextInt(255), rand.nextInt(255), rand
					.nextInt(255)));
			g.drawOval(rand.nextInt(60), rand.nextInt(20), 1, 1);
		}

		g.dispose();

		request.getSession().setAttribute("strRand", strRand);
		ImageIO.write(img, "jpeg", response.getOutputStream());
	}

}