HttpSession invalidate issue + serialization

Question

The set up of my code is as follows:
* Applet communicates with Servlet(s)
* ServletA keeps a HashMap of session objects with an attribute as key.
* Once logout is called in applet - a call comes to servlet in form of a seriallized request object.
* After sessions is invalidated, second line of code is to send back a serialized response object back
* This is where I receive what seems to be a java.io.EOF exception
Reading up on invalidate() didn't seem to shed any light on anything similar happening except for the fact that the object's bindings are lost. Would that mean that I am not able to write on the response from servlet back to applet once I destroy session inside sevlet??
Thank you in advance.

Answer 1

My code here:
HttpSession session = this.getRequest().getSession();This is the current session. The new one.
//sessionID - getting existing session ID from DBHow you get this is unstated, but let that pass.
HttpSession oldSession = (HttpSession)session.getAttribute(sessionID);As I said before, this is nonsense. How can the old session possibly get into the attributes of the new session? Who put it there? Magic? What makes you think a session is available by sessionID from any servlet API at all? Hint: it isn't.
oldSession.invalidate(); //getting exception hereTrivially that's because 'oldSession' is null and you're not even checking it. You should have figured that out for yourself. You don't seem to have even considered the possibility that it is null, let alone the probability that the reason is that the previous line of code which set it is invalid. Instead you are just asking for a workaround to make your preconceived code work, when what you should be doing is asking about the validity of your preconceptions.
I find all that pretty strange frankly.
I also find the underlying requirement pretty strange. What if the user is logged in at two workstations simultaneously? Logging in at the second one will forcibly log him out of the first one. Why?