How to take previous value during refresh of a servlet

Question

I hava a servelt. I am using the following code to refresh.

res.addHeader("Refresh", "10");

But before I am reading the date using a form.

For the first time, it works fine. But after 10 sec, during refresh I am getting null pointer exception as date is null.

How to take the previous value of date even after refresh.

thanks in advance, Mahes

Answer 1

The simplest solution is probably to save the date in the session.

If the value is present on the request (post) store the value in the session.

session.setAttribute("queryDate",theDate);

When reloading, check if getParameter() returns null and use the date from the session using getAttribute().

Answer 2

Putting the value in session is one valid option.

Another option is, on the first submission, to add a hidden field to the form that contains the previously submitted date. On refresh, the hidden field will be submitted, so the date will still be part of the request parameters.