Re: Page flow with some business logic

[Erik Weber]

Yes, having methods along the lines of "ensureXXXX" and "doXXXX" that 
are paired makes sense and I have seen the strategy work well. The 
challenge is that you often want these two methods to be invoked within 
a single transaction context. For example, you don't want to return true 
from ensureXXXX, then something happens which would cause ensureXXXX to 
return false before you invoke doXXXX. (But of course you still want to 
account for the case in which that does happen.) You probably don't want 
your Struts Action to have to worry about managing transactions; so 
probably your Struts Action invokes some delegate method 
(moveIfPossible?) that either returns a success code/value or throws an 
Exception. The delegate encapsulates transactional behavior (or hides 
the fact that atomicity isn't ensured yet ;) ) and interacts with some 
manager layer component on behalf of your Actions. I'm not saying "this 
is how you do it", more just giving you food for thought.

Take a look at "Core J2EE Patterns" (awesome book) and/or the Sun J2EE 
blueprints site for some patterns and idioms.

Erik
Nic Werner wrote:
Hi,
   Big picture, I have a form that gives you the ability to 'move' an 
object. I'd like to check to see if the destination location already 
exists so nothing would be overwritten. If something does exist, I'd 
like to output what object (and its values) is there, and do a 
confirmation screen. Can someone help on how I would do this type of 
logic with Struts?

Would it work if I had a business function called CanMove() that 
returned the object at that destination and null if the destination 
was empty? If null, I would just call my Update() function? If not 
empty, have Struts forward to a confirmation screen? Is this the 
proper convention?

I apologize that this isn't totally Struts related, but this forum has 
been great at ensuring I don't re-invent the wheel.

- Nic.
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