Hi,
Just a quick note to say thanks for the input. I'm going to have to brush up
on my Avalon knowledge before I can understand the impact of such an
approach - gains, losses, level of effort, etc - and make any meaningful
comments.
One thing that immediately troubles me is how Mailet pipelining would work.
Currently we have a Linear Processor that is responsible for workflow;
invoking Mailets based on a mail's state. I'm guessing that you guys would
advocate a workflow service to provide the equivalent function?
-- Steve
> From: Albert Kwong wrote:
> Sent: 22 June 2004 08:57
> To: Stephen McConnell; James Developers List
> Subject: Re: My Status, and James RoadMap
>
>
> > >>Albert Kwong recently sent to me a patch detailing
> > a
> > >>MailetRegistry that
> > >>handles the registration of merlin based mailet
> > >>implementations (without
> > >>touching the mailet api). This is consistent with
> > the ideas I've
> > >>discussed with Alexis Agahi (Open IM) - basically
> > that the really
> > >>interesting scenario is the ability to move james
> > from
> > >>"application" to
> > >>"service" and once that is achieved - to be able
> > to use james as just
> > >>another service available to any other component.
> > >
> > >
> > > That would be something worth examining. Any links
> > to the conversations?
> >
> > It was off-list so I can't quote anything but I have
> > pinged Albert to
> > let him know that I'm talking about him and this
> > subject. What I can
> > say is that he has come up with a modified james
> > assembly model which
> > ties in a mailet registry - which is kind of cool.
> > It does not impact
> > the mailet api but enables component based mailets.
> > After looking at
> > the code (which is based on Merlin 3.2 I think we
> > can improve/simplify
> > this using the composition spi in Merlin 3.3.
>
> As Steve said, the proposed solution uses a mediator
> with the following interfaces:
>
> public interface RegistryService
> {
> public void register (String name, Object
> plugin);
> public Object resolve (String name);
>
> public void addListener (String name, Listener
> listener);
> }
>
> public interface Listener
> {
> public void registryReady () throws Exception;
> }
>
> A Mailet component will implement the standard Mailet
> interface as well as Avalon lifecycle interfaces. In
> particular, during service(), it looks up the
> RegistryService and then registers itself during
> initialize().
>
> The JamesSpoolManager component will implement the
> Listner interface and adds itself to the registry
> during initialize(). When the RegistryService
> confirms that all components are ready, it calls the
> listener's registryReady() method, where actual
> initialization can take place.
>
> The block.xml will contain the following:
>
> <component name='mailet-registry'
> class='RegistryService'>
>
> <plugin-type>org.apache.mailet.Mailet</plugin-type>
> <plugin>CustomAvalonMailet</plugin>
> <listener>JamesSpoolManager</listener>
> </component>
>
> <component name='custom-mailet'
> class='CustomAvalonMailet'>
> <configuration>...</configuration>
> </component>
>
> <component name='transport'
> class='org.apache.james.transport.JamesSpoolManager'>
> <!-- ... -->
> <mailet name='CustomAvalonMailet' type='avalon'>
> <!-- ... -->
> </mailet>
> </component>
>
> When the JamesSpoolManager sees that a mailet is of
> type avalon, it can use the RegistryService to lookup
> the component instead of looking it up from the
> predefined mailet packages.
>
> Benefits: the CustomAvalonMailet can make use of any
> avalon services, such as a datapath we have designed.
> The datapath can be shared between the web tier and
> the SMTP tier (and potentially many other tiers),
> making code highly reusable. In our case, we did not
> call any James Avalon services from our servlets.
>
> Albert
>
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