Need some Help on this peculiar issue.

Question

The following code is there in Controller Servlet.
Sometimes in a very random fashion this code fails.
The code is as follows.
========================= CODE START =========================
public void doPost
(HttpServletRequest objRequest, HttpServletResponse objResponse) {
navigate(objRequest, objResponse);
private void navigate
(HttpServletRequest objRequest, HttpServletResponse objResponse) throws IOException,ServletException {
try {
System.out.println("strFromScreen : '" + strFromScreen + "' strAction : '" +
strAction + "'");
objEpsNavigation = hashLookUp(strFromScreen, strAction);
if (objEpsNavigation == null) {
strErrorJSP = "jsp/EpsErrorPage.jsp";
CMUtility.log("Navigation Object is not created");
displayErrorPage
(objRequest,objResponse,"Navigation Object is notcreated !!");
return;
========================= CODE END ==========================
System.out.println("strFromScreen : '" + strFromScreen + "' strAction : '" + strAction + "'");
The above line in the code is printing null. Not everytime. Very often suddenly it gets null value and hashLookUp(strFromScreen, strAction) returns null object.
So, system shows the error page with error message "Navigation Object is notcreated !!".
Please help me in this regards.
It is not happening regularly, it's happening randomly.
Thanks in advance.
- Pratip

Answer 1

Where have you defined and assigned values to 'strFromScreen ' and 'strAction' .
If these are instance variables then, unless you have instructed the servlet engine to create a new servlet instance for each request, near simultanious requests will interfer with one another.
It is normal to make servlets thread safe which, as a starting point, normally means no instance variables.