生成随机验证码图片

package com.gnnuit.response;

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;

//生成验证码图片
public class ServletResponseDemo3 extends HttpServlet {
	private static final long serialVersionUID = 1L;
	private static int WIDTH = 120;
	private static int HEIGHT = 25;

	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		//设置客户端不要缓存
		response.setHeader("Expires", "-1");
		response.setHeader("Pragma", "no-cache");
		response.setHeader("Cache-Control", "no-cache");
		// 1、创建内存图片，BufferedImage
		BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
				BufferedImage.TYPE_INT_RGB);
		// 2、通过图片获得画笔Graphics
		Graphics g = image.getGraphics();
		// 2.1画边框
		g.setColor(Color.BLUE);
		g.drawRect(0, 0, WIDTH, HEIGHT);
		// 2.2画背景颜色
		g.setColor(Color.GRAY);
		g.fillRect(1, 1, WIDTH - 2, HEIGHT - 2);
		// 2.3画干扰线9条
		g.setColor(Color.YELLOW);
		Random r = new Random();
		for (int i = 0; i < 9; i++) {
			g.drawLine(r.nextInt(WIDTH), r.nextInt(HEIGHT), r.nextInt(WIDTH),
					r.nextInt(HEIGHT));
		}
		// 2.4画验证码数字4个
		g.setColor(Color.RED);
		g.setFont(new Font("宋体", Font.BOLD, 20));
		int x = 7;
		for (int i = 0; i < 4; i++) {
			g.drawString(r.nextInt(9) + "", x, 20);
			x = x + 30;
		}
		// 3、输出内存图像到客户端ImageIO
		ImageIO.write(image, "jpeg", response.getOutputStream());
	}

	protected void doPost(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {

	}
}