Re: [MO-java-users] any pattern for this?

[J. X. <sou...@ma...>]

Quoting Nat Pryce <nat...@b1...>:

> Your object should make use of interfaces that make sense to it, not
> that are defined by technology that you have chosen.  This is what mock
> objects are good for: in TDD they drive the design of an object's
> *required* interfaces.

Sometimes, it does make sense to define an abstract interface between a client 
and its vendor, but not all the time, especially when the usage of the vendor 
requires strong assumptions.  In this castor case, castor's (rather intrusive) 
usage paradigm has made a lot of impact on my code, e.g., all the classes 
handled by the marshalling engine must have either public getters/setters or 
have their own castor-dependent handlers.  Another example is that I had to 
make special wrapper classes simply because the XML unmarshaller cannot 
effectively unmarshal a map.  From the design point of view, it would be just 
illusional to have an "un/marshaller interface" and pretend to have the ability 
to "plug in" another un/marshaller.

Well, my question is, then, do mock objects drive, or do they actually *force* 
the design? Following this pattern, wouldn't I have to define interfaces for 
every 3rd party class I use that does not support a factory, in order to be 
able to plug in my own mocked version of those classes?

--J.X.

> 
> Your object needs to unmarshall some data from some input stream.  The
> interface should express that.  An implementation of the interface can
> use the castor API.  But if you drive the design of the interface from
> the needs of your object, not from your choice of castor, then it will
> be easy to change your choice of XML API later if you want.  Using mock
> objects to drive the design of the interactions between your objects
> will naturally lead to such "flex points" in your design.
> 
> Cheers,
> 	Nat.
> 
> 
> 
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