Re: component vs. general classes

[Stephen McConnell]

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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Stephen J. McConnell

OSM SARL
digital products for a global economy
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