Re: Publisher - Subscriber pattern for Tapestry Service

On Sun, Jun 18, 2017 at 12:52 PM, abangkis <[email protected]> wrote:

> Lets say I have a hashtag entity that i stored in the database and managed
> by HashtagDAO (a tapestry service).  And then i have a TwitterParserService
> that check if a tweet contain a hashtag that i saved in the database. The
> problem, if someone add or changed the hashtag in the database i want the
> TwitterParserService to immediately know about the change and check the
> tweet using the new hashtags.
>
> In j2se it will be a straight forward pub-sub/observer pattern. Just create
> an interface for the listener, let the TwitterParserService implement it
> and set as the default listener, and invoke it from HashtagDAO. But i don't
> think it would work with tapestry services class.
>

Why wouldn't it work? Tapestry itself uses this: LinkCreationHub,
RegistryStartup, InvalidationEventHub, RegistryShutdownHub,
UpdateListenerHub, and that's just the ones I've found in a two-minute
search. It would all be synchrononous, though, and messaging services, as
far as I know, are asynchronous.

--
Thiago