[Smartfrog-developer] RE: Finding components...

[Guijarro, J. <jul...@hp...>]

> -----Original Message-----
> From: Glenn Hisdal [mailto:hi...@st...]
> Sent: 18 June 2004 11:14
> To: Guijarro, Julio
> Cc: sma...@li...
> Subject: Re: Finding components...
> 
> Hello,
> 
> Guijarro, Julio wrote:
> 
> >>>> Did you try to advertise SF references?
> >>>
> >>> No, didn't try that. Since a reference can be built from a canonical
> >>> name, I guess I could advertise them in the same way and just rebuild
> >>> the reference from the canonical name when it is received ?
> >>>
> >>> [JULIO] Yes, but sometimes can be better to send the Reference
> >>> object.
> >>> The
> >>> most important feature is that References can contain indirections.
> >>> And
> >>> these indirections can be completely dynamic. It is also easier to
> >>> work with
> >>> native Refs than Strings ;-)
> 
> So the Reference object can contain information that will not be
> included when it is converted to a canonical name String ?

Not, with its actual implementation there is a one to one mapping. But
creating a reference from a string implies loading the parser and it is a
heavy operation. Also, when using the SF language it could be that the data
that you want to adv. is a Ref or a String or a Int or a RMI stub, ... you
don't know in advances and it should not be hard coded.

Example: using "advertise" attribute to select what to advertise:
       advertise 1; -> advertises Integer 
       advertise LAZY x; -> advertises RMI stub to a component;
       advertise LAZY extends ComponentDescription; -> advertises a
component description
       advertise "hola"; -> advertises a string;

       advertise LAZY sfCannonicalName; -> I will make this available;
                                         -> advertises cannonicalName;
       advertise LAZY sfProcessComponentName; -> advertises processName
       advertise LAZY sfHost; -> advertises host name;
       advertise [1,2,3]; -> advertises vector.


> In order to just locate the Component, the canonical name should always
> work, right ?

Yes unless something changes in its parentage chain.

> So, I could have something like this:
> Advertise component:
> service:sf-prim:///<canonical_name_string>
> Advertise SF reference to component:
> service:sf-reference:///<string_encoded_reference_object>
> 
> This could probably be handled by the PrimAdvertiser component. An
> attribute could say if it should advertise the component, the reference
> or both.
> A ReferenceLocator could be written to find and return a reference to a
> component. i.e:
> refLoc extends ReferenceLocator;
> primLoc extends PrimLocator;
> sfConfig extends Compound {
> 	theReference LAZY refLoc:result;
> 	theComponent LAZY primLoc:result;
> }
> 
> It would probably also be useful if the components could return a
> Vector of all the discovered components/references ?

It should be up to the component to select what to advertise.
> 
> > Can you advertise any arbitrary object in the same way you advertise
> > rmi
> > stubs?
> 
> It should be possible to make a String representation of any
> serializable object and add that to the URL path.
> This would be similar to the Reference advertisement:
> service:<some_type>:///<string_encoded_object>
> 
> I could make some extensions to the ServiceURL class allowing it to
> handle objects in an easy way:
> - contructor which can take an object and automatically convert it to a
> String.
> - A method getURLPathObject() which will convert the URLPath to an
> object and return the object (if possible).
> 
> 
> - glenn