在response中使用Cookie，求助！
<%@page   import= "javax.servlet.http.Cookie.java.util.* "%>
<%
String   username= "liuning "
Cookie[]   cookie=request.getCookies();
Cookie   cookie_response=null;
List   list=Arrays.asList(cookie);//query   List,Attays
Iterator   it=list.iterator();//query   Iterator
while(it.hasNext())
{
Cookie   temp=(Cookie)it.next();
if(temp.getName().equals(userName+ "_access_time "))
{
cooke_response=temp;
break;

}
}
out.println( "now "+new   java.util.Date()+ " <br> ");
if(cookie_response!=null)
{
out.println( "last   time   you   visited: "+cookie_response.getValue());
cookie_response.setValue(new   Date().toString());
}
else
{
cooke_response=new   Cookie(username+ "_access_time ",new   java.util.Date().toString());
}
response.addCookie(cookie_response);
response.setContentType( "test/heml ");
response.flushBuffer();
%>

报错：
HTTP   Status   500   -  

--------------------------------------------

type   Exception   report

message  

description   The   server   encountered   an   internal   error   ()   that   prevented   it   from   fulfilling   this   request.

exception  

org.apache.jasper.JasperException:   Exception   in   JSP:   /response.jsp:6

3:   String   username= "liuning ";
4:   Cookie[]   cookie=request.getCookies();
5:   Cookie   cookie_response=null;
6:   List   list=Arrays.asList(cookie);//query   List,Attays
7:   Iterator   it=list.iterator();//query   Iterator
8:   while(it.hasNext())
9:   {


Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:506)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:395)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


root   cause  

java.lang.NullPointerException
java.util.Arrays$ArrayList. <init> (Arrays.java:3357)
java.util.Arrays.asList(Arrays.java:3343)
org.apache.jsp.response_jsp._jspService(response_jsp.java:50)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:334)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)


note   The   full   stack   trace   of   the   root   cause   is   available   in   the   Apache   Tomcat/5.5.20   logs.

请高手赐教！


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