Precheck the MQTT payload / problem with jsonpath

[NoLimit (Niko)]

Hi Folks,

i have a small issue using Xiaomi Sensors with Sonoff ZbBridge and receiving the sensor date via MQTT in OpenHAB 3.

The Thing and Channel configuration is working fine i can receive the data.
Im Using JSONPATH to receive the needed value from the json string.

transformationPattern: JSONPATH:$.ZbReceived.Tp_GstKlo.Contact

But…
…one of the behavior of Tasmota is that it is sending payloads for different “events” on the same MQTT topic!
The result is, that there are not always the expected values in the payload.

Here is an example:
Expected payload with the needed “Contact” value:
{ "ZbReceived": { "Fr_GsKlo": { "Device": "0xA8D1", "Name": "Fr_GsKlo", "Contact": 1, "Endpoint": 1, "LinkQuality": 92 } } }

and then there are sometimes payloads like this:
{ "ZbReceived": { "Fr_GsKlo": { "Device": "0xA8D1", "Name": "Fr_GsKlo", "BatteryVoltage": 3, "BatteryPercentage": 98, "Endpoint": 1, "LinkQuality": 63 } } }

As you can see there is no “Contact” value.
The result is that i get a lot of warnings like this:
Executing the JSONPATH-transformation failed: Invalid path '$.ZbReceived.Fr_GsKlo.Contact' in '{"ZbReceived":{"Fr_GsKlo": "Device":"0xA8D1","Name":"Fr_GsKlo","BatteryVoltage":3,"BatteryPercentage":98,"Endpoint":1,"LinkQuality":63}}}'

Now my question is:
is it somehow possible to “pre-check” the payload and discard the payload in case the needed value is not there?
I would really like to get rid of these warnings.

Cheers
Niko

[hafniumzinc (T)]

@NoLimit

is it somehow possible to “pre-check” the payload and discard the payload in case the needed value is not there?

Yes, use the REGEX Transformation Service, then chain the JSONPATH Transformation Service afterwards.

MQTT 2.5 M1+ How to implement the equivalent to MQTT1 REGEX filters

Problem In the MQTT1 binding there was a feature that let us filter messages published to a given topic and only pass those that match a given REGEX to the transformation and/or on to the Item. This was useful to handle devices that publish messages to a single well known topic for all their devices. For example, the official firmware from the vendor of Shelly devices have a request/response protocol over MQTT to get meta data about the devices (IP address, MAC address, firmware version, whethe…

[Joerg_Schreiner (Jörg Schreiner)]

Hi,
you have to chain with REGEX transformation.
First a REGEX transformation of the payload and then the JSON transformation afterwards.
I don’t have the exact nomenclature at hand, but if Noone else can support, I will look into it tomorrow.
Joerg

[NoLimit (Niko)]

Hey guys,

many thanks for the replay!
And dear god it seems like i was to stupid to search for the the right stuff here.
Sorry for creating double threads…

Anyway the hint with REGEX seems to work fine:
transformationPattern: REGEX:(.*Contact.*)∩JSONPATH:$.ZbReceived.Tp_GstKlo.Contact

Cheers
Niko