一个用JAVA实现验证码的实例

package com.gyhqq.web.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.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 = 20 * 4;
		int height = 28;
		// 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.GRAY);
		graphics.drawRect(0, 0, width - 1, height - 1);
		// 5、设置字体颜色和属性
		graphics.setColor(Color.RED);
		graphics.setFont(new Font("宋体", Font.BOLD, 22));		
		// 随机输出4个字符
		String s = "ABCDEFGHGKLMNPQRSTUVWXYZ23456789";
		Random random = new Random();		
		// session中要用到
		String msg = "";		
		int x = 5;
		for (int i = 0; i < charNum; i++) {
			int index = random.nextInt(32);
			String content = String.valueOf(s.charAt(index));			
			msg += content;
			graphics.setColor(new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255)));
			graphics.drawString(content, x, 22);
			x += 20;
		}
		// 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 {
	}
}