Spring @Controller lifecycle

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.