http://java.sun.com/products/java-media/jai/


　　1. random.jsp (产生四位的随机字符,由0-9,a-z,A-Z构成.并把最终字符串放到session中保存以让后续页面验证真伪)

　　代码如下:

<%@ page autoFlush="false" import="java.util.*,java.awt.*,java.awt.image.*,
com.sun.image.codec.jpeg.*,java.util.*"%>

<%@ page import="" contentType="text/html; charset=gb2312"%>

<%

String chose=
"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
char display[]={'0',' ','0',' ','0',' ','0'},ran[]={'0','0','0','0'},temp;
Random rand=new Random();
for(int i=0;i<4;i++)

{
temp=chose.charAt(rand.nextInt(chose.length()));
display[i*2]=temp;
ran[i]=temp;

}



String random=String.valueOf(display);
session.setAttribute("random",String.valueOf(ran));

%>

<%
out.clear();