Q:

Can we consider a design pattern as a tier in j2ee application

Recently i got this question in my interview..
He had asked me about N tier ,I was telling him about 3 tier applications Suddenly he asked me Can i have 5 tiers :) I told him may be but i never used that..
IV: Ok now tell me what can be the 5 tiers
ME: BLa bla
After the interview i asked him for the answer and he gave me a example like below
Web or client layer -> delegate(pattern)Ejb layer(business)->value objects(pattern)-Implemenatation of dao layer-then ur db 
He added one more point when your application talks with another application then urs will be N tier application 
Is it so friends?

A:

I think he confused tiers with layers.
In an architecture, tiers are the coarsest building blocks, seperating concerns like presentation, business logic and persistence, sometimes even in a physical manner. However, a design can introduce additional layers for reasons like reusability, but that doesn't affect the number of tiers the architecture is made of.

A:

Here is an example (I'm not saying follow it, only hardware vendors and application servers vendors like to sell this monster):

Client Tier: browser
Presentation Tier: Servlet/JSP
Service Tier: Session Beans
Domain Tier: Entity Beans (writing this makes my eyes bleed).
EIS Tier: database

Now, to answer your question, a design pattern is certainly not a tier in itself. But a tier can be made of components implementing a pattern (e.g. the Session Beans of the Service Tier implement the Facade pattern). 

