Re: [xmlblaster] Notifying Clients

[Marcel Ruff <mr at marcelruff.info>]

chris lau wrote:
> Hi,
>
> I am trying to setup a situation where client A publishes a PTP message to client B. Client B
> subscribes for updates using the callback method. The problem I'm running into is that I want
> Client B to get a notification that a message has arrived but I *do not want* to remove the
> message from the queue. Client B will then use the get() method at a later time to retrieve the
> message.
>   
If it is only one message which B is waiting on you could throw a
 "user.update.holdback"
(see 
http://www.xmlblaster.org/xmlBlaster/doc/requirements/interface.update.html)
during update(), like this B is notified and the message remains in the 
servers callback queue.
After retrieving the message with get() you can set the 
dispatcherActive=true again.

Another possibility is that B logs in as B/1 and B/2.
If the PtP is send to B, both session will receive it.
Now B/1 gets it consuming over update() and is 'notified'.
B/2 didn't specify a callback server and did set dispatcherActive=false 
during connect().
Now B/2 uses sync get()s only to retrieve.

Still another solution is to use a receive() call setting consuming=false.
(see 
http://www.xmlblaster.org/xmlBlaster/doc/client-api/org/xmlBlaster/client/I_XmlBlasterAccess.html#receive(java.lang.String,%20int,%20long,%20boolean)
Now B blocks and returns when the message has arrived ("notifiy").
Later, you can call receive() with consumable=true to access and destroy it.

Another possibility is to have another login session to  subscribe on 
the PtP topic
and is like this notified. B has set dispatcherActive=false already 
during connect
and only uses get() or receive() synchronously whenever needed.

Probably there are some more ways to solve it,

regards
Marcel
> What is happening now is that as soon a Client A publishes a message and the update() method of
> Client B is triggered, the message is removed from the queue.
>
> I've tried to set the subscribeQos.setWantContent to false, but that doesn't keep the message in
> the queue.
>
> So, basically, here is the sequence of events.
> 1. Client B connects and subscribes for updates.
> 2. Client A connects and publishes a message.
> 3. Client B receives a notification that a message has arrived. Message remains in queue.
> 4. A period of time elapses...
> 5. Client B retrieves message contents. 
> 6. Client B removes message from queue (if not done automatically)
>
> Is xmlBlaster able to do this?
>
> Thanks.
>
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around 
> http://mail.yahoo.com 
>
>