Seeking Clarification on Implementation of The Business Logic Com ponents

["Goldberg, Joel S" <jo...@eds.com>]

> In the Struts User Guide at
> <http://jakarta.apache.org/struts/userGuide/introduction.html>  The
> statement is made:
> 
> "For the simplest applications, an Action object may sometimes handle the
> business logic associated with a request. However, in most cases, an
> Action object should invoke another object, usually a JavaBean, to perform
> the actual business logic. This lets the Action focus on error handling
> and control flow, rather than business logic. To allow reuse on other
> platforms, business-logic JavaBeans should not refer to any Web
> application objects. The Action object should translate needed details
> from the HTTP request and pass those along to the business-logic beans as
> regular Java variables. "
> 
> It seems clear that the author advocates the business logic to be
> separated from, and ignorant of, web environment classes (even Struts
> classes) to maximize reusability.   But we need help to settle a
> misunderstanding of what is meant by the term "JavaBeans" in this passage.
> 
> 
> Question 1: Which interpretation is correct:
>     1.  The Business Logic should be in vanilla Java Classes that perform
> the business logic and follow Java Bean protocol (such as using getters
> and setters).  
>          It doesn't seem that introspection to allow visual development is
> relevant here - hence the confusion over the meaning of "JavaBean."  
>     2.  All business logic that has been factored out of the Action should
> be in EJBs.  
>     3.  Either 1 or 2 depending on what makes sense to make into EJBs.
> 
> Then if  the answer to Question 1 is  1 or 3,  I have two follow on
> questions:
> 
> Question 2:   Is it okay for the business logic classes to run on the same
> tier (JVM) as the Action?
> Question 3:   Is it okay to create separate instances of the business
> logic classes to remain thread safe or should they be Singletons (as the
> Actions are).  If they are JavaBeans, this seems to imply the are instance
> based (i.e. not singletons) and thus can have instance variables as
> needed. 
>  
> One last question,  if the answer is that they could be EJBs,  what
> criteria do you apply to determine good candidates for EJBs? 
> 
> Please elaborate on any of the above as you see fit.
> 
>  
> 			Joel Goldberg 
> 
> 

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