When is a Servlet class loaded and instantiated?

[Timothy Sam]

I'm passed through the Servlet chapter in HFSJ but I think I didn't get how the Servlet class is first loaded. I get the impression that the idea of the Servlet class being loaded on the first deploy/startup of the container is somehow vendor-dependent.

Also, is possible for the init() method not to be called when the Servlet is instantiated? Thanks!

[Tarun Yadav]

AFAIK, the specification doesn't mandate when the container should load a servlet ( unless using <load-on-startup> ).

So the container can load and instantiate the class whenever it needs to. By using <load-on-startup>, you can be sure that your servlets will be loaded when the app is starting up and be available. Otherwise, the order is pretty much random and on a need-to basis. A servlet may be ready and waiting for requests, or it may be loaded and initialized only when a request comes for it.

And I'm not very sure about this but yes, I don't think it's necessary for the init() to be called immediately when the servlet is instantiated. But it must be called before the servlet can service any requests.

[Timothy Sam]

Hi Tarun

Thank you very much. I think I'm very satisfied with your explanation. Thanks!