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From Andrew Timberlake <and...@ddd.co.za>
Subject [Fwd: Re: Mailet API]
Date Mon, 22 Apr 2002 16:00:05 GMT
Thanks Dave for the response
I'm forwarding this thread back into the list as I would like to hear
the main developers, and others, feedback and insight into this.

Thanks

Andrew

-----Forwarded Message-----

From: Dave Morris <dave.morris@codon.demon.co.uk>
To: Andrew Timberlake <andrew@ddd.co.za>
Subject: Re: Mailet API
Date: 22 Apr 2002 16:19:22 +0100

Yep.
Quite true.
However, kind of makes the Matcher redundant if all the Mailets start doing their
own matching.

I kind of like the separation of functionality, a Matcher filters the messages
and a Mailet does stuff with the messages. What I want to add is a way of the
Mailet an Matcher to talk to each other, mainly to share configuration
information.

This came up when I was experimenting with designing some of my own custom
Mailets.
In each case, the Mailet needed to process emails to one or more addresses in a
list or group.
Both the Mailet and Matcher needed to be configured to access the same list of
addresses.

I kept ending up with an odd situation where both the Mailet and Matcher share
the same list of addresses, but they can't communicate directly with each other.

Much like the current RecipientIsLocal Matcher and LocalDeliver Mailet, both have
to use an Avalon lookup to get a reference to the local reporistory, but they
can't talk to each other.

You are right, it is possible to implement using the current API, just a few
extra hoops to jump through.
The proposed change would just make it a little easier to design Matcher and
Mailet combinations.
If it causes too many side effects, then it isn't worth it.

Thanks,
Dave


Andrew Timberlake wrote:

> Just a quick question.
> A mailet can perform the function of a matcher just by virtue of
> checking the mail message as it processes it. Therefore could you not
> achieve what you are looking for with the match="ALL" and then write
> "matching" information into the mailet?
>
> Andrew
>
> On Mon, 2002-04-22 at 14:21, Dave Morris wrote:
> > Hi,
> >
> > I would like to propose a change to the Mailet API, and would be
> > interested in thoughts and ideas.
> >
> > At the moment, Mailets have no access to their Matcher.
> > I appreciate that this is probably by design.
> > However ..... I would like to suggest adding the following to the Mailet
> > API.
> >
> >      /**
> >       * Create a Matcher for this Mailet.
> >       * Default is to return null and let the container create the
> > Matcher.
> >       * Advantage is that the Mailet can use it's internal data to
> > generate and configure a suitable Matcher.
> >       * Disadvantage is that the Mailet interface becomes tied to the
> > Matcher interface.
> >       *
> >       */
> >      public Matcher getMatcher() ;
> >
> > And changing the code which loads the Mailets and Matchers in
> > JamesSpoolManager to this.
> >
> >     Mailet mailet = null;
> >     Matcher matcher = null;
> >     //
> >     // Allow blank 'match' attribute in config XML.
> >     String matcherName = c.getAttribute("match", null);
> >     //
> >     // Load the Mailet.
> >     mailet = loadMailet(mailetClassName, mailetcontext, c) ;
> >     //
> >     // If the config specified a Matcher.
> >     if (null != matcherName)
> >         {
> >         matcher = loadMatcher(matcherName, mailetcontext) ;
> >         }
> >     //
> >     // If not, see if the Mailet has it's own Matcher.
> >     else {
> >         matcher = mailet.getMatcher() ;
> >         }
> >     //
> >     // If we still don't have a Matcher.
> >     if (null == matcher)
> >         {
> >     //
> >     // Two possible options.
> >     // a) Throw an Exception saying "No Matcher specified for Mailet".
> >     // b) Add a default 'All' Matcher.
> >     // Depends which people think makes more sense ....
> >     //
> >         }
> >
> > This does not break any of the existing Maliets or configuration.
> > All of the existing mailets can implement the new method and return
> > null, leaving the container to configure the Matcher.
> > All of the exisiting configuration stays the same, any Matcher specified
> > in the config will override the Matcher generated by a new Mailet.
> >
> > As an example of what this change would gain, consider the local
> > delivery Mailet and Matcher.
> >
> >     <mailet match="RecipientIsLocal" class="LocalDelivery"/>
> >
> > In order to check if the recipient is a local user, the Matcher needs to
> > access the local repository.
> > In order to store the mail, the Mailet needs to access the local
> > repository.
> >
> > Two separate components, both of which need be configured to access the
> > local repository.
> >
> > If the LocalDelivery Mailet was able to generate it's own Matcher, then
> > the configuration could be changed to this.
> >
> >     <mailet class="LocalDelivery"/>
> >
> > In this example, the Mailet would create it's own RecipientIsLocal
> > Matcher.
> > Not much of an advantage as yet.
> > However, the domain for the Mailet could be configurable, so we could
> > have this.
> >
> >     <mailet class="LocalDelivery">
> >         <domain>mydomain.com</domain>
> >     </mailet>
> >
> >     <mailet class="LocalDelivery">
> >         <domain>myother.com</domain>
> >     </mailet>
> >
> > In each case, the Mailet would generate it's own Matcher, configured to
> > match recipients for the specified domain.
> > Yes, I know it is possible to implement this example using the current
> > API.
> >
> >     <mailet match="RecipientIsInDomain=mydomain.com"
> > class="LocalDelivery">
> >         <domain>mydomain.com</domain>
> >     </mailet>
> >
> >     <mailet match="RecipientIsInDomain=myother.com"
> > class="LocalDelivery">
> >         <domain>myother.com</domain>
> >     </mailet>
> >
> > However, providing a link between the Mailet and Matcher would make it
> > easier to create more complicated Matcher/Mailet combinations to handle
> > dynamic lists of addresses.
> >
> > Any thoughts ?
> >
> > Thanks,
> > Dave
> >
> >
> >
> >
> > --
> > To unsubscribe, e-mail:   <mailto:james-dev-unsubscribe@jakarta.apache.org>
> > For additional commands, e-mail: <mailto:james-dev-help@jakarta.apache.org>
> >
> --
> Andrew Timberlake
> Digital Design Development
> http://www.ddd.co.za
> mailto:andrew@ddd.co.za
> 011 705 1737
> 082 415 8283
>
> "If debugging is the process of removing bugs,
> then programming must be the process of putting them in."


-- 
Andrew Timberlake
Digital Design Development
http://www.ddd.co.za
mailto:andrew@ddd.co.za
011 705 1737
082 415 8283

"If debugging is the process of removing bugs, 
then programming must be the process of putting them in."


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