jsp验证码加无刷新更新

JSP做无刷新的验证码：
一共两个页面：
第一个image.jsp
一下是Image.jsp源代码
[java]
<%@ page language="java" import="java.util.*,java.awt.image.*,java.awt.*,javax.imageio.*" pageEncoding="GBK" contentType="image/jpeg"%>

<%!
Color getRandColor(int start,int end,long seed)
{
    if(start>255)
    {
        start=255;
    }
    Random random=new Random(seed);
    int r=start+random.nextInt(end+1-start);
    int g=start+random.nextInt(end+1-start);
    int b=start+random.nextInt(end+1-start);
    return new Color(r,g,b);
}
%>
<%
int width=60;
int height=20;
//随机产生的验证码中的字母,可以设置多一点
String[] str={"1","a","A","B","c","2","I","8","U","y"};
BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
//这就算是有纸了，需要知道宽度高度
Graphics g=image.getGraphics();
//这就算有笔了

g.setColor(getRandColor(230,250,System.currentTimeMillis()));
//这就算把笔蘸上颜色了
g.fillRect(0,0,width,height);
//填充底色
Random random=new Random(System.currentTimeMillis());
//画干扰线
g.setColor(getRandColor(160,200,System.currentTimeMillis()));
for(int i=0;i<50;i++)
{
    g.drawLine(random.nextInt(6),random.nextInt(15),
    random.nextInt(6)+random.nextInt(56),random.nextInt(7)+random.nextInt(17));
}

String check=new String();

g.setFont(new Font("Times new Roman",Font.PLAIN,18));
for(int i=0;i<4;i++)
{
    g.setColor(getRandColor(20,110,System.currentTimeMillis()+i*1000));
    //String ran=String.valueOf(random.nextInt(10));
    int temp=random.nextInt(10);
    String ran=str[temp];
    check+=ran;
    g.drawString(ran,6+i*13,16);//分别往上写数字
}
//可以通过session来获取随机产生的验证码
session.setAttribute("check",check);

g.dispose();
//使图像生效
//response.setCharacterEncoding("GBK");
//request.setCharacterEncoding("GBK");
ImageIO.write(image,"JPEG",response.getOutputStream());
//将图像输出，三个参数分别为纸，格式，服务器相应的输出流

out.clear();
out=pageContext.pushBody();
//加上这两句，tomcat就没有异常信息

%>

然后在其他地方使用。
[html]
<body>
    <img src="image.jsp" id="code"/> <a href="#" onclick="reload()">刷新</a>
     <script>
    function reload(){
        document.getElementById("code").setAttribute("src","image.jsp?a="+new Date().getTime());
    }
    </script>
</body>

补充：Web开发 , Jsp ,