Question

I am new to Spring MVC and would like to know how it handles requests, more specifically:

1. I would like to know how a Spring
   @Controller’s life cycle relates to
   that of a Servlet?
2. I would also like to better
   understand what are the best
   practices for multi-threaded
   enviornments (e.g. like in Servlets,
   are class attributes visible to
   multiple HTTP requests as objects are
   reused from the pool)?

Answer 1

A controller (as any spring bean) has a scope.

At best your controllers should be of scope singleton. In that case it is very much like servlets, and:

• they are created only once, during the application context startup (and destroyed when the context is destroyed)
• you should not use any instance variables (as this is not thread-safe)

If your controller scope is request or session, then you can have instance variables, and an instance of the controller is created on each new request/session.