Private instance variable in servlet set to null?

Question

In my servlet I start a background thread onContextInitialized() and consequently I need to stop it onContextDestroyed(). So my servlet needs a private instance variable (let's call this daemon) pointing to this daemon thread. The daemon runs fine, but the reference is lost as soon as I exit contextInitialized()! For example, if I implement doGet() to show the status of the thread, it throws a NPE

So the answer is, who can access my servlet private instance variable and set it to null? I remark that the thread runs just fine, just the reference is broken

Answer 1

Just set the reference in Application Context or set it to some static field of some class[less preferable]

Not sure what you want to achieve but this will do

Answer 2

Make it static so all instances can see it:

private static Thread daemon;