J Aaron Farr wrote:
On Mon, 2003-09-01 at 00:19, Niclas Hedhman wrote:
Stephen McConnell said:
This is why I would "promote" the solution of setAbc() for dependency resolution and a more generic lookup() for service discovery.
Niclas
There's no reason we can't have multiple dependency resolution schemes.
Sure.
For example, we could support all three IoC types (as defined by the PicoContainer project). I do something like that in my JingDAO project already. This would also allow us to better support:
- older Avalon components - traditional JavaBeans - Pico-style components
One issue would be determining which dependency scheme to use. It could potentially be done dynamically by first trying the contructor, then any bean properties and finally via the service() method. The meta-info might also be able to store this information, but I would like it to be as automagical as possible, making it easier for component writers.
You would have to include this in meta - the risks are simply too high that the container interacts with the component in an unexpected way.
In the end though, you'll still be stuck with older Avalon components which use the service manager for both dependencies and discovery. I personally would like to see the service manager used more for discovery than dependency resolution.
Frankly I don't think the current ServiceManager interface is a good candidate for dynamic service discovery. It does not provide support for the supply of a selection policy and its exception suite needs to be beefed up a lot.
This could be handled by doing something like:
public interface Locator
{
Object lookup( Criteria criteria ) throws
ServiceUnknownException,
ServiceUnresolvableException,
ServiceUnavailableException;
} public interface ServiceLocator
extends ServiceManager, Locator{}We can easily provide a selectable serviceable strategy such that a ServiceLocator could be supplied directly as in:
public void service( ServiceLocator locator ) trhows ServiceException
{
// stuff
}While enabling different modes of Locator usage as a pure service .. e.g.:
public class HelloComponent
{
public HelloComponent( Logger logger, Locator locator )
{
// constructor stuff
}
}Or, classic service lookup:
public void service( ServiceManager manager )
{
m_locator = manager.get( Locator.class.getName() );
}Steve.
I'm working on some ideas for this now -- should have something a little more concrete tomorrow. Any other thoughts or comments would be appreciated.
--
Stephen J. McConnell mailto:[EMAIL PROTECTED]
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