Session variable incorrect value

Hi

I have a drop down <select> in jsp having city names. Current city value comes from session attribute.
On change Java script function is called which through AJAX calls second jsp which updates the session
attribute value with new city.

From it's response I can see correct city value is being passed and attribute is being reset correctly.

But after the first jsp reloads, it is not using correct attribute value.

When I change from Delhi to Gurgaon, it stays Delhi
If I change to Noida, it changes
But then if I try to change to anything else it just stays at Noida

I have spent few hours trying to diagnose but I am not able to get the underlying issue

Kindly suggest what may be wrong

Code

First jsp

// Purpose Sets user city

function setCity ()

{
              var xmlHttp;

try
  {

// Firefox, Opera 8.0+, Safari  xmlHttp=new XMLHttpRequest();

xmlHttp=new XMLHttpRequest();

}

catch (e)
  {  // Internet Explorer  try
       xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");

{    try
      {      xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");      }
    catch (e)
      {            return false;      }    }  }

xmlHttp.onreadystatechange=function()
    {

// alert (xmlHttp.readyState);
        if(xmlHttp.readyState==4)
      {
        alert (xmlHttp.responseText) ;
        window.location.reload () ;

}
    }

var ele = document.getElementById('usercity') ;
  //alert (ele.selectedIndex + ' , ' + ele.options [ele.selectedIndex].text) ;
  var city = ele.options [ele.selectedIndex].text ;

xmlHttp.open("GET","index1.jsp?city=" + city  ,true);
  xmlHttp.send(null);

}     // setCity ends

</script>

</head>
    <body>

<%

// user city drop down list generation, current city shown as selected

String cityList [] = {"Delhi","Gurgaon","Noida"} ;   // pick from database after scaling up
                String defaultCity = "Delhi" ;   // default city

// if at start session attribute is not created, it would be created and initilized with default city

if (session.getAttribute("userCity") == null)
                    {
                     //out.println ("Null check in city drop down") ;
                     session.setAttribute("userCity",defaultCity) ;

}
                else
                    {
                    // out.println ("2 session attribute not null") ;
                    }

String currentCity = (String) session.getAttribute("userCity") ;
                //out.println ("2 current city is " + currentCity) ;
                for (String city : cityList)

{
                  //  out.println ("Inside for loop " + currentCity) ;
                        if (city.equals (currentCity))

{
                                out.println ("<option selected=\"true\">" + city + "</option>") ;
                            }

else
                            {
                            out.println ("<option>" + city + "</option>") ;
                            }

}

%>
                        </select>

Second jsp

Your browser is caching the responses to your ajax calls. You can see this if you add logging into your second JSP.
The first couple work, but after that, it just returns a cached response without actually invoking the server.

Suggestion:
Change

to

The rules of caching are different for get and post requests.
GET is assumed to be cachable.
POST for the most part is not.
If you are actually changing something (which you are) you should POST, rather than GET.

If that doesn't work then take a look at the JSP FAQ: No-Cache Headers

Thanks a lot Stefan Evans.

By changing request type to POST , it's working fine.