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From Eddie Bush <>
Subject Re: Architecture advice....
Date Mon, 29 Jul 2002 21:37:44 GMT
David Graham wrote:

> Now we're onto "how to design a factory method" :-).  So if you have 
> many different service objects you could just compose your 
> ServiceFacade of these objects and publish their interfaces.  This is 
> the true use of the facade pattern so your code doesn't need to know 
> about all of the objects behind the facade.  You would do this like so:
> ServiceFacade{
> private SpecialServiceClass special;
> public doService(){
>   special.doService(); //delegate call to internal service object
> }
> }
> Notice that all interaction with SpecialServiceClass is done through 
> the facade leaving you free to rip out SpecialServiceClass in the 
> future and replace it with something else.
> If you really want to do the factory thing you have 2 options:
> 1.  A factory method for each service class
>  public SpecialServiceClass createSpecialServiceClass()...
>  public SpecialService2 createSpecialService2()...
> 2.  One factory method with parameter telling which type of service 
> class to return.  public Object create("SpecialServiceClass")
> I would go for the facade pattern so most of your code only knows 
> about the facade and not the implementation classes.
> I hope this helps. 

Why not name your services.  Then, use a properties file to figure out 
what the actual class is.  If all you ever programmed to was an 
interface, you could switch implementations out very easily.  Just edit 
the properties file and restart you app!


... then ...

public ServiceInterface create("serviceName")

Ummmm - I believe that addresses any concerns you may have, but I sure 
welcome suggestions! ;-)

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