26 Apr
2009
26 Apr
'09
2:06 a.m.
Tharindu Madushanka wrote:
Hi,
I have been looking at how to notify when an event has been finished. Here
what I have currently understood and I got some confusion.
In order to get notified when login event finished, I think I have to do the
following things.
1. Create a LoginListener class that implements EventListener
Yes
2. Create object of DefaultObservationManager class
(DefaultObservationManager implements ObservationManager)
No, the component manager
will give you the right instance. You should
read about this here: http://en.wikipedia.org/wiki/Inversion_of_control
and here:
http://platform.xwiki.org/xwiki/bin/view/DevGuide/WritingComponents
All you need to do is declare a dependency on the ObservationManager
component.
3. Define class UserLoginEvent similar to
DocumentSaveEvent
Yes
4. call addListener() of ObjectManager interface
(using
DefaultObjectManager) with parameters - object of UserLoginEvent and
reference to login listener.
Yes. This is done by the client that wants to be
notified of login
events, which is different from the class sending those events.
5. get reference to DefaultObjectManager instance
See the observation on 2.
6. call notify() of DefaultObjectManager instance when
user successfully
logged in, with parameters - object of UserLoginEvent, doc and context
Yes. The
tricky part is knowing when this happened, or what is the code
that knows that.
7. Implement notify() in LoginListener class.
Yes.
Q. But I have several confusions when I looked at
XWiki class,
saveDocument()
1. Where does it create and add a listener to ObservationManager object??
2. And also it takes ObservationManager object from Util.getComponent()but
where does this observationManager instance is added or set ?
The component manager takes care of instantiating objects. There are
several component frameworks, from the heavier Spring and OSGi to the
lightweight picocontainer and Guice. We're currently using Plexus for this.
So, com.xpn.xwiki.XWiki does not create an instance of
ObservationManager, it gets one from the ComponentManager through the
Util class. Normally, other components should just declare a dependency
on the needed component, and the CM would automatically inject it,
without any calls to Util.getComponent, but the XWiki class is not a
component yet, so it is not managed by the component manager. The code
inside the xwiki-core module is not made of components yet, while most
of the other core modules are 100% components, with a few exceptions
(xwiki-webdav and xwiki-rest).
Please clarify me on what I currently understood and
let me know if its the
right steps to go with.
Yes, the steps are almost right. Good job so far.
--
Sergiu Dumitriu
http://purl.org/net/sergiu/