Re: [RT] Merlin & Persistence (was: [RT] Component Persistence)

[Stephen McConnell]

Alexis Agahi wrote:

I'll explain below.

   

Should home define method that
will be used by provider to establish persitence? (if yes, then this
sounds nice ,))
     

Here is a move detailed breakdown of the terms I'm using:

 * identifiable component - an instance of a identifiable component type
 * identifiable component type - a type that includes an <indentifiable>
      elements declaring a home interface
 * home - a component implementing a home interface
 * home interface - defintion of storage value creation, query
      and destruction operations
 * home component - a component that implements the home interface
      and handles storage value creation query and destruction
      using some persistence solution
So for example, lets imagine we have something called a User and that
we maintain multiple users.  From this we would need:
Interfaces:

 * User - an service interface
 * UserStorage - an interface defining operation on a user storage
     value instance
 * UserHome - the home interface
Classes:

 * DefaultUser - an identifiable component
 * DefaultUserStorage - a class implementing UserStorage using a
     particular persistence solution
 * DefaultUserHome - implementation of the UserHome
A container on deploying a identifiable component would locate and
deploy a component implementing the UserHome service, get an instance of
UserStorage from the home and add this to the identifiable
components context.
   



Ok so here, UserStorage/DefaultUserStorage are here to define persistence 
methods for the component User/DefaultUser? (right?)

Correct.

Dont you think compent (User/DefaultUser) could implement itself the 
appropriate method (of DefaultUserStorage) to persiste itself and 
Home/interface/Impl would find directly the appropriate component?

One could do that - however - I have found that it is a good idea to 
seperate the persistent object from the functional object.  This enables 
different types of user components that use a common persistent model.

Cheers, Steve.

(this remind me a scene from MontyPython HolyGrail ;))

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Stephen J. McConnell
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