验证码程序

<%@ page autoFlush="false" import="java.awt.*,java.awt.image.*,com.sun.image.codec.jpeg.*,java.util.*"%>
<%@ page import="org.apache.commons.lang.RandomStringUtils"%>
<% 
RandomStringUtils rs=new RandomStringUtils();
String random=rs.randomAlphanumeric(4);
session.setAttribute("random",random);
%>
<%

out.clear();
response.setContentType("image/jpeg");
response.addHeader("pragma","NO-cache");
response.addHeader("Cache-Control","no-cache");
response.addDateHeader("Expries",0);
int width=100, height=40;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
//以下填充背景?色
g.setColor(Color.GRAY);
Font DeFont=new Font("SansSerif", Font.PLAIN, 32); 
g.setFont(DeFont);
g.fillRect(0, 0, width, height);
//?置字体?色
g.setColor(Color.RED);
g.drawString(random,3,30);
g.dispose();
ServletOutputStream outStream = response.getOutputStream();
JPEGImageEncoder encoder =JPEGCodec.createJPEGEncoder(outStream);
encoder.encode(image);
outStream.close();