自己实现一个验证码功能

用Servlet技术实现验证码功能，（画出一个验证码）

公司中一般用写好的验证码（jar包），很少使用自己去画验证码 。

package chensi.com;

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.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet 用Servlet实现输出验证码   (自己画出的验证码)
 */
@WebServlet("/ResponseDemo8")
public class ResponseDemo8 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
                //告诉客户端不使用缓存
                response.setHeader("pragma", "no-cache");
                response.setHeader("cache-control", "no-cache");
                response.setIntHeader("expires", 0);

                //自己画出一个验证码
                int width = 110;
                int height = 25;

                //在内存中创建一个图像对象
                        BufferedImage img = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

                        //创建一个画笔
                        Graphics g = img.getGraphics();

                        //给图片添加背景色
                        g.setColor(Color.PINK);//设置一个颜色
                        g.fillRect(1, 1, width-2, height-2);//填充颜色

                        //给边框一个色
                        g.setColor(Color.RED);
                        g.drawRect(0, 0, width-1, height-1);//设置边框的显示坐标

                        //设置文本样式
                        g.setColor(Color.BLUE);
                        g.setFont(new Font("宋体", Font.BOLD|Font.ITALIC, 15));

                        //给图片添加文本
                        Random rand = new Random();
                        int position = 20;
                        for (int i = 0; i < 4; i++) {
                            g.drawString(rand.nextInt(10)+"", position, 20);//给图片填充文本
                            position+=20;
                        }

                        //添加9条干扰线
                        for (int i = 0; i < 9; i++) {
                            g.drawLine(rand.nextInt(width), rand.nextInt(height), rand.nextInt(width), rand.nextInt(height));
                        }
                        //将图片对象以流的方式输出的客户端
                        ImageIO.write(img, "jpg", response.getOutputStream());

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}