Dennis Kang wrote:
If compared with J2EE, could we say components in
Avalon is similiar with J2EE conceptually? For
example, if we have a Avalon version of Pet store
compared with J2EE version, should we design most of
the entities such as ShoppingCart, Product, Customer,
etc. as components?
In a word - Yes.
At the level of granularity your talking about I would
expect to see these abstractions as services exposed by
a set of classicv components.
Steve.
Dennis.
--- Stephen McConnell <[EMAIL PROTECTED]> wrote:
Dennis Kang wrote:
Is there any design principle when to use
components
and when to use general classses?
I tend to view things in less absolute terms:
1. there are objects that have no component
notions
2. there are object that leverage component
notions
but are not pure compoennts (i.e. not
deployable
within a particular "standard" container
3. there are pure components which are typiclly
targetted towards deployment under a "standard"
containment environment
Example of case 2:
public class MyClassLoader extends URLClassLoader
implements LogEnabled
{
Logger m_logger;
public MyClassLoader( URL[] urls )
{
super( urls );
}
public void enableLogging( Logger logger )
{
m_logger = logger;
}
public Logger getLogging()
{
return m_logger;
}
}
However, it does not take much to turn our example
classloader object
into a full component. All that is needed is a null
argument constructor.
In reality you have
OOP -- grey zone -- COP/SOP
Being grey should not be considered a bad thing -
sometime you need a
little tone in life.
:-)
Cheers, Steve.
Thanks.
Dennis.
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