Version: 3.2.12

Chain Transformation Profile Service

The CHAIN profile allows chaining multiple transformations.


The profile has three configuration parameters:

Empty chains result in pass-through of the original value. Individual transformations are chained with the mathematical intersection character ().

Example: Door lock

A lock that can report its status and accepts commands in JSON. It shall be represented as a Switch item on openHAB.

Incoming values (toItem)

The received value for the status is { "device" : { "status" : { "lock" : "locked" }}} or { "device" : { "status" : { "lock" : "unlocked" }}}. The transformation needs to first extract locked or unlocked and then map those values to ON or OFF.

The first part is done by using the JSONPATH transformation: $.device.status.lock.

The second part is done by using the MAP transformation using a file


So the full toItem transformation is


Outgoing values (toChannel)

For setting the lock's state we need to produce another JSON: {"device" : { "command" : "lock" }} or { "device" : { "command" : "unlock" }}. The transformation needs to do the inverse of the above: first map ON or OFF to lock or unlock and then insert that into a JSON-template.

For the first part we again use the MAP transformation and extend the map from above:


For the second part we use the FORMAT transformation with a doorlock.format:

{ "device" : { "command" : "%1$s" }}

The fulltoChannel transformation is∩FORMAT:doorlock.format

Sidenote: Of course, it would have been easier to just use the MAP transformation and enter the full JSON string as target value.