1) can we call System.exit(0) in servlet's life cycle methods (eg service)?
What would be the point of that? You'd be trying to force the JVM to quit, and thus the servlet container to stop. That's why servers in a production settings run with a security manager enabled, which prohibits calls to System.exit (amongst other things).
2) Can we call destroy explicitly from service method?[/QB]
init and destroy are servlet lifecycle methods, which are called by the servlet container. You
can call them, but you absolutely
should not.