Mule MEL check for NullPayload vs null

Question

According to the following ticket: https://www.mulesoft.org/jira/browse/MULE-6427 For NullPayload I should be able to use :

<when expression="#[payload == null]">

but that fails. So instead I have to use:

<when expression="#[payload is NullPayload]">

Am I doing something wrong? Or is this the correct way for checking for null or NullPayload?

score 9 · Answer 1 · answered Jan 12 '15 at 20:30

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In theory, this should be fixed, but it doesn't looks like so. I'm using CE 3.4.0 and the expression #[payload == null] doesn't work for NullPayload.

I've found this link that shows how to check if payload is NullPayload correctly:

#[payload is org.mule.transport.NullPayload]

I actually needed to know if payload was not NullPayload, so my expression was:

#[!(payload is org.mule.transport.NullPayload)]

Works like a charm. :)

answered Jan 12 '15 at 20:30

mathielo

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Thanks @mathielo, I was going crazy. The [MULE-6427](https://www.mulesoft.org/jira/browse/MULE-6427) said it was fixed and even their [MEL expression page](http://www.mulesoft.org/documentation/display/current/Mule+Expression+Language+Tips) says you should be able to use `#[payload == null]` but only your solution works for me. Many thanks again! – Doug Ayers Apr 02 '15 at 19:34
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Thanks, you helped me :) Mulesoft is very poor documented :( – Dariusz Mydlarz Apr 09 '15 at 14:17

score 4 · Answer 2 · edited Mar 20 '16 at 11:52

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In Mule 3.7, (Studio 5.2) for a NullPayload, #[payload == null] now returns true. Interestingly, #[payload is NullPayload] returns false.

edited Mar 20 '16 at 11:52

eebbesen

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answered Jul 15 '15 at 21:13

user1274293

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Anirban Sen Chowdhary · Answer 3 · 2017-11-01T19:45:03.627

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Try this to check:

#[payload == empty]

edited Nov 01 '17 at 19:45

answered Dec 05 '14 at 15:50

Anirban Sen Chowdhary

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As in Collection.isEmpty() ? My payload is not a collection so there will be no method isEmpty(). Do you have the same issue with == null then? I can get around the issue by using instanceof. The main issue is that I should be able to use == null – jon lee Dec 05 '14 at 16:31

score 1 · Answer 4 · edited Mar 20 '16 at 11:53

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This works on version 3.5: #[payload is NullPayload]

edited Mar 20 '16 at 11:53

eebbesen

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answered Jun 05 '15 at 14:55

Miguel Martinez

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score 0 · Answer 5 · answered Dec 05 '14 at 15:24

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This seems to be still true in the very lastest version of Mule as per this code.

This won't work if you are at a version < than 3.4

answered Dec 05 '14 at 15:24

Víctor Romero

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I'm using 3.5.1. #[payload == null] fails if the payload is NullPayload – jon lee Dec 05 '14 at 15:33

score 0 · Answer 6 · answered Apr 11 '19 at 11:38

This is quite interesting.

The expression which is not working for you is working for me:

<when expression="#[!(payload == null)]">

and interestingly the other suggestions (listed below) are not giving the expected results:

<when expression="!(payload instanceof org.mule.transport.NullPayload)">
<when expression="#[!(payload is org.mule.transport.NullPayload)]">
<when expression="#[!(payload is NullPayload)]">

Mule MEL check for NullPayload vs null

6 Answers6