HTTP binding send JSON body in PUT request (restful api)

Add-ons Bindings
1

I’m trying to configure a switch on a Hue behaviour. Reading works, writing does not. I tried the documentation, but even as a software engineer, I do not understand how this is supposed to work.

I simply need it to post {"enabled": true} or {"enabled": false} depending on the switch state. There’s a only a single example in the docs for dynamic urls, but that’s a GET edge case. Can somebody please provide an example on how to work a REST API?

UID: http:url:sz_wakeup_light
label: HTTP URL Thing
thingTypeUID: http:url
configuration:
  authMode: BASIC
  headers:
    - hue-application-key=<hidden>
  ignoreSSLErrors: true
  baseURL: https://<hidden>/clip/v2/resource/behavior_instance/adc2736e-f3fd-465c-8206-f061ae50115c
  delay: 0
  stateMethod: GET
  refresh: 30
  commandMethod: PUT
  contentType: application/json
  timeout: 3000
  bufferSize: 2048
channels:
  - id: enabled
    channelTypeUID: http:switch
    label: enabled
    description: ""
    configuration:
      onValue: "true"
      stateContent: '{"enabled": %2$}'
      offValue: "false"
      stateTransformation: JSONPATH:$.data[0].enabled

Toggling a switch on this thing leads to an internal object reference to be posted. Is this a bug or a missing configuration? I cannot see which configuration item might produce this.

Requesting 'https://<hidden>/clip/v2/resource/behavior_instance/adc2736e-f3fd-465c-8206-f061ae50115c' (method='PUT', content='org.eclipse.jetty.client.util.StringContentProvider@1acd7f1') failed: 400 Bad Request

1 Like
2

you want to have a commandTransformation

Maybe try

commandTransformation: JSONPATH:$.enabled

3

JSONPATH extracts data from JSON, it does not hav a reverse function.

I think you’re fighting the onValue/offValue, these are bi-directional and apply to outbound commands too.

4

There is an enhancement request in for a formatBeforePublish parameter, akin to the one in the MQTT binding. That would do the trick, if implemented.

5

IMO this should be done by a proper transformation. If the required format is more complex than the one presented above, it’s not so easy to put it in one input field.

6

Thanks. So the stateContent is only used to build a request body in the Pull-Case, but commandTransformation forms the body in the reverse direction.
I put in a jinja transformation JINJA:{"enabled": {{value}} }. This works for my case.

The Jinja transformation has value_json for json-structured values. Leaves the question how more complex states would be represented (e.g. brightness, color) towards the transformation plugin.

This part should be documented both better and with a more complex example.

7

Oh, this is interesting: could you share your updated full Thing YAML?

1 Like
8 
UID: http:url:wakeup_light
label: HTTP URL Thing
thingTypeUID: http:url
configuration:
  authMode: BASIC
  headers:
    - hue-application-key=<hidden>
  ignoreSSLErrors: true
  baseURL: https://<hidden>/clip/v2/resource/behavior_instance/adc2736e-f3fd-465c-8206-f061ae50115c
  delay: 0
  stateMethod: GET
  refresh: 30
  commandMethod: PUT
  contentType: application/json
  timeout: 3000
  bufferSize: 2048
channels:
  - id: enabled
    channelTypeUID: http:switch
    label: enabled
    description: ""
    configuration:
      onValue: "true"
      commandTransformation: 'JINJA:{"enabled": {{value}} }'
      offValue: "false"
      stateTransformation: JSONPATH:$.data[0].enabled

There is no authentication since this is using a preshared key, disabling authMode is not available but basic with no username/password works.

The uuid of the behaviour needs to be looked up through https://<hidden>/clip/v2/resource/behavior_instance/.

1 Like
9

Just a warning. The OpenHab Jinja transformation “JinJava” seems to be very limited, if not crippled. Most functions or even string formatting doesn’t work. So while Jinja would be a good and powerful tool for this kind of problem, the Jinja transformation seems not to be.
The Javascript transformation is working for other cases but you have to create a file per snippet and plain Javascript is very inefficient to write.

10

I have a need to POST a string from a String Item, but embedded within some JSON. I’m currently doing this with a proxy Item and a rule, but am looking to get rid of these extras. This JINJA transformation might be what I need, so thanks for sharing!

I’m trying to avoid JS transformation as you can’t define this within the UI, as you say.

EDIT: Well, that worked a treat! Thanks again for sharing this - I’ve put in a PR to the JINJA documentation to give an outgoing transformation example.

1 Like
11

Hello, thanks for sharing this… Do you think it will work for a JSON like this (for an elgato light) ?

{
    "numberOfLights": 1,
    "lights": [
        {
            "on": 1,
            "brightness": 20,
            "temperature": 200
        }
    ]
}```
12

Well, it seems it does work, i can turn on and off the elgato light… Now I need to refine a bit the state side of the story.

13

Hello

I ma using openhab since more than a yer now, and i would be interested in this type of command sending (i acquired a oekofen boiler, which is working through json api). Could you post the JINJA path you used for this “complex” elgato thing ?

Regards
J