怎么样通过java代码得到页面上的验证码

<%@ page contentType="image/png" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %><%
//设置页面不缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

int width=40; //设置图片宽度
int height=20; //设置图片高度

//创建缓存图象
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics(); //获取图形

g.setColor(new Color(000, 102, 153)); //设置背景色
g.fillRect(0, 0, width, height); //填充背景

g.setColor(new Color(000, 000, 000)); //设置边框颜色
g.drawRect(0, 0, width-1, height-1); //绘制边框

g.setFont(new Font("Arial", Font.PLAIN, 16)); //设定字体

Random random = new Random(); //生成随机类

//随机产生3位