Re: [xmlblaster] New to xmlBlaster and have questions...

[Heinrich Götzger <goetzger at gmx.net>]

Kelli,

On Thu, 21 Nov 2002, Kelli Fuller wrote:

>I am involved in developing an interface between 2 systems using xmlBlaster
>with Java and a publish/subscribe architecture. Being new to xmlBlaster, I
>have some pretty basic questions that I am hoping someone can answer for me:
>
>1. Is it possible to edit the content of a message that has been published
>and is sitting in the xmlBlaster queue? Or would I have to subscribe to that
>message, create an XML file containing the message's contents plus the edit
>I need to make, then publish that message again?

You just need to (re)publish it with the new content.
The previous content will be overridden then.

The content does not necessarily have to be XML-Data. All data you can
convert to bytes can be a content.

see
http://www.xmlblaster.org/whatis.html
for more details.


>
>2. What exactly does unsubscribe do for me? What are some uses for it? Is
>there a way to call unsubscribe on a message that will then prevent a
>subsequent subscribe call from seeing the unsubscribed message?

You 'll have to erase the message.


But, there is some nice feature, if you subscribe to some message,
unsubscribe, disconnect, connect and then (re)subscrbe to the same
message, you will get the latest message in the queue.

excerpt from the Requirements:
http://www.xmlblaster.org/xmlBlaster/doc/requirements/engine.qos.subscribe.initialUpdate.html

On subscribe you can prevent the initial message update for existing messages.

Description

Imagine a message exists already in xmlBlaster. If you subscribe for this
message you will receive an initial update for this existing message
(default behavior). In some cases you want to prevent this to only receive
an update when a new message is published after subscription.

If you set the subscribe QoS to

<qos>
   ...
   <initialUpdate>false</initialUpdate>
</qos>


you won't receive the initial update triggered by the subscription.

Heinrich