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MQSeries.net Forum Index » WebSphere Message Broker (ACE) Support » Element existence check, followed by empty value test

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Mut1ey
PostPosted: Wed Mar 16, 2011 9:10 am    Post subject: Element existence check, followed by empty value test Reply with quote

Acolyte

Joined: 07 Oct 2005
Posts: 74
Location: England
A general query. Based on an XSD we have some optional elements in the XML(NSC) tree, surprise surprise.

We want to execute path A if the element either does not exist or has a null/ empty string value, or execute path B otherwise. So path A if element does not exist in incoming tree or does exist but is empty. Path B only if element exists and has a non-zero length value.

In ESQL I would use IF EXISTS syntax to confirm that the element exists and then check the element value for the empty string (""). A colleague is using the IF element IS NOT NULL syntax which seems to do both the check for existence and also for null/ empty string value. This is during a debug session, so the debug may be doing something additional. Either way, what approach do you use in this case?

Using broker toolkit and runtime 6.1.4 on windows XP.
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kimbert
PostPosted: Wed Mar 16, 2011 10:34 am    Post subject: Reply with quote

Jedi Council

Joined: 29 Jul 2003
Posts: 5542
Location: Southampton
Those are three separate conditions, and your code should check for them separately.
- IF EXISTS to see whether the field is in the message tree
- IS NULL / IS NOT NULL to check whether it has an explicit null value
( for XMLNSC this is only possible if xsi:nil=true in the xsd )
- FIELDVALUE(fieldref)="" to check whether the field is the empty string.
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