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Which tier does Business Delegate belong to?

Felix Sima
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Joined: Feb 06, 2008
Posts: 42

I am using maven to build my web application. Maven suggests to have a separate project for each artifact (ear, war, ejb-jars).
My doubt is where to place my business delegates?
The J2EE core design patterns catalog places the business delegate in the business tier, but then, in the "solution" chapter of the business delegate it says "The Business Delegate acts as a client-side business abstraction...".
Should I place my business delegate in the war or in a jar(beside the ejb-jars)?
By the way, what is the difference between a tier and a layer? Is it correctly to say that the business delegate belongs to the business tier but not to the business layer?

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Jimmy Clark
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Joined: Apr 16, 2008
Posts: 2187
My doubt is where to place my business delegates?

A Presentation-tier Business Delegate implementation which acts as a client-side business abstraction should be part of the web application and placed in a WAR file with the other Presentation-tier code.

It is possible to have a Business-tier Business Delegate (this is what is described in the design pattern documentation also.) If the business logic in your application interacted with another application, it would encapsulate access to that other application's business methods via Business Delegate. Here your application is a client of the other application.

In my experience, Presentation-tier Business Delegates are the norm, and the other type is rare.

The J2EE programming model is based on three-tier programming. The tiers are: Presentation, Business and Integration.

The term "layer" is another term that is used with other technologies and designs and pre-dates the J2EE programming model. It causes a lot of confusion and does not have a concise definition.
Ronald Wouters
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Joined: Apr 28, 2005
Posts: 190
The difference between tiers and layers is clearly defined in the
This white paper describes Sun's own "version" of the unified process and the image of "the cube" (url above, on page 12) will make things much clearer.

[ December 08, 2008: Message edited by: Ronald Wouters ]

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Sun Certified Enterprise Architect for the Java Platform, Enterprise Edition 5
I agree. Here's the link:
subject: Which tier does Business Delegate belong to?
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