Single Thread Model

[sitaram irrinki]

A servlet implements Single Thread model
public class BasicServlet extends HttpServlet implements SingleThreadModel {

int number = 0;
public void service(HttpServletRequest req, HttpServletResponse res) {
}
}
Which is thread safe ?
(a) Only the variable num
(b) Only the HttpServletRequest object req
(c) Both the variable num & the HttpServletRequest object req

[David O'Meara]

Sounds like a homework question.
Answer this one first please: What do you think?

[Makarand Parab]

Sitaram
It's Deprecated. As of Java Servlet API 2.4, with no direct replacement.

public interface SingleThreadModel
Ensures that servlets handle only one request at a time. This interface has no methods.

If a servlet implements this interface, you are guaranteed that no two threads will execute concurrently in the servlet's service method. The servlet container can make this guarantee by synchronizing access to a single instance of the servlet, or by maintaining a pool of servlet instances and dispatching each new request to a free servlet.

Note that SingleThreadModel does not solve all thread safety issues. For example, session attributes and static variables can still be accessed by multiple requests on multiple threads at the same time, even when SingleThreadModel servlets are used. It is recommended that a developer take other means to resolve those issues instead of implementing this interface, such as avoiding the usage of an instance variable or synchronizing the block of the code accessing those resources. This interface is deprecated in Servlet API version 2.4.

So David what u think.