Shared objects in servlet?

Question

Consider this code snippet
public class MyServlet extends HttpServlet {  
//declare session object
private HttpSession session;
public void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
session = req.getSession(true);
// get a value
String value_of_id = req.getParameter("some_name");
session.setAttribute("myid",value_of_id);
Now the question
Will a new instance of servlet be spawned for each incoming request?
Is the session object declared in servlet level shared among all servlet instances?
If Yes, Is there a possibility that the value of 'my_id' for request#1 will be owerwritten by the value set from request#2?

Answer 1

#1 - No servlets are multithreaded.
So essentailly there is only instance but many threads processing a request?Correct.
#2 - Yes All servlets and JSP's in the same servlet context can access a session.
Will the servletcontext for servlet-thread#1 be the same as servletcontext for servlet-thread#2
Yes. Servlet context is the webapp the servlets are running.
http://localhost:8080/test/servlet/myServlet
Here the context is /test.
#3 - No. The servlet container assigns each session a unigue id so that each request will only access the session associated with requests from a specific browser.
So essentially the concept of shared objects apply to Httpsession objects?
When the servlet encounters request.getSession() it checks the request for a session cookie. It takes the session id from the cookie and retrieves the HttpSession object for that request. The servlet is multi threaded but each thread has it's own copy of the local variables so as long as you do not put the session object in a global variable each request will see a seperate session object. Therefore sessions are not shared objects.
A request is a thread.