JSONPATH transformation in item

Setup, Configuration and Use Beginners
1

I’m configuring JSONPATH transformation for the first time and seems to be missing something basic. Please advise.
This is the item:
String Sonoff1info "Sonoff #1 startup info [%s]" { mqtt="<[broker:tele/sonoff1/RESULT:state:JSONPATH($.Info1.Version)]" }

And this is the raw JSON received from the broker:
{"Info1":{"AppName":"Sonoff 8266 Module", "Version":"3.2.13", "FallbackTopic":"DVES_XXXXXX", "GroupTopic":"sonoffs"}}

My goal is to extract:
a) single value like "3.2.13"
b) name with value like “Version”:"3.2.13"
c) the whole string like it was before the firmware author switched to JSON

At the moment I’m getting:
[WARN ] [pse.smarthome.core.items.GenericItem] - failed notifying listener '[org.eclipse.smarthome.core.persistence.internal.PersistenceManagerImpl@ee100e1, Sonoff1info, null]' about state update of item java.lang.NullPointerException: {}

2

have you tried

String	Sonoff1info "Sonoff #1 startup info [%s]" { mqtt="<[broker:tele/sonoff1/RESULT:state:default]" }

and do you see the complete message in the item?

1 Like
3

Yes, but… Here is the thing - in fact I’m getting 2 responses:

tele/sonoff1/RESULT {"Info1":{"AppName":"Sonoff 8266 Module", "Version":"3.2.13", "FallbackTopic":"DVES_XXXXXX", "GroupTopic":"sonoffs"}}
tele/sonoff1/RESULT {"Info2":{"WebserverMode":"Admin", "Hostname":"sonoff1-XXXX", "IPaddress":"192.168.X.X"}}

Without transform I see the 2nd result only.

4

You migh have success getting only from the message containing Info1 if you use the optional REGEX filter documented here.

5

Do you mean REGEX instead of JSONPATH or in addition to JSONPATH?

6

In addition to. It’s an optional additional section after the transform.

7

No error and no update of the item. Added per example from the docs:
String Sonoff1info "Sonoff #1 startup info [%s]" { mqtt="<[broker:tele/sonoff1/RESULT:state:JSONPATH($.Info1.Version):REGEX(.*\"Info1\".*)]" }

Oops, works without REGEX word.
Thanks!

1 Like
8

So this worked?

String	Sonoff1info "Sonoff #1 startup info [%s]" { 
  mqtt="<[broker:tele/sonoff1/RESULT:state:JSONPATH($.Info1.Version):.*\"Info1\".*]" 
}
9

Yes, this works, but I was not able to harden the filter by checking for leading {
Constructions like \{*\"Info1\".* or .*\{\"Info1\".*are not working, but I can live with this.

Currently I can grab the individual values as well as the whole string by using JSONPATH($.Info1)

{AppName=Sonoff 8266 Module, Version=3.2.13, FallbackTopic=DVES_XXXXXXX, GroupTopic=sonoffs}
How can I get rid of {} ?