validcodeimggen.java

用JSP完成根据用户的身份实现登录识别的下载

package com.mypack.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.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ValidCodeImgGen extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		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();
		g.setFont(new Font("Arial", Font.BOLD, 16));

		String validCode = "";
		for (int i = 0; i < 4; i++) {
			g.setColor(new Color(rand.nextInt(128), rand.nextInt(128), rand
					.nextInt(128)));
			int randNum = rand.nextInt(10);
			validCode += randNum;
			g.drawString(String.valueOf(randNum), 6 + i * 13, 16);
		}
		for (int i = 0; i < 100; 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("validCode", validCode);
		ImageIO.write(img, "jpeg", response.getOutputStream());
	}
}