生成验证码

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
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;

public class CodeServlet extends HttpServlet {

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

			// 使用java图形界面技术绘制一张图片

			int charNum = 4;
			int width = 30 * 4;
			int height = 30;

			// 1. 创建一张内存图片
			BufferedImage bufferedImage = new BufferedImage(width, height,
					BufferedImage.TYPE_INT_RGB);

			// 2.获得绘图对象
			Graphics graphics = bufferedImage.getGraphics();

			// 3、绘制背景颜色
			graphics.setColor(Color.YELLOW);
			graphics.fillRect(0, 0, width, height);

			// 4、绘制图片边框
			graphics.setColor(Color.BLUE);
			graphics.drawRect(0, 0, width - 1, height - 1);

			// 5、输出验证码内容
			graphics.setColor(Color.RED);
			graphics.setFont(new Font("宋体", Font.BOLD, 20));

			// 随机输出4个字符
			Graphics2D graphics2d = (Graphics2D) graphics;
			 String s = "ABCDEFGHGKLMNPQRSTUVWXYZ23456789";
			Random random = new Random();
			//session中要用到
			String msg="";
			int x = 5;
			for (int i = 0; i < 4; i++) {
				int index = random.nextInt(32);
				String content = String.valueOf(s.charAt(index));
				msg+=content;
				double theta = random.nextInt(45) * Math.PI / 180;
				//让字体扭曲
	            graphics2d.rotate(theta, x, 18);
				graphics2d.drawString(content, x, 18);
				graphics2d.rotate(-theta, x, 18);
				x += 30;
			}

			// 6、绘制干扰线
			graphics.setColor(Color.GRAY);
			for (int i = 0; i < 5; i++) {
				int x1 = random.nextInt(width);
				int x2 = random.nextInt(width);

				int y1 = random.nextInt(height);
				int y2 = random.nextInt(height);
				graphics.drawLine(x1, y1, x2, y2);
			}

			// 释放资源
			graphics.dispose();

			// 图片输出 ImageIO
			ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
		

		}
	

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

	}

}