Read data from URL

Setup, Configuration and Use Beginners
1

Hi,

I have a water protection device which has a web API presumably returning JSON data. Unfortunately I have no clue how to get it into OpenHab 3.

The URL is http://192.168.20.18:5333/safe-tec/get/BAR and results in

<html>
<head>
  <meta name="color-scheme" content="light dark">
</head>
<body>
  <pre style="word-wrap: break-word; white-space: pre-wrap;">
    {"getBAR":"4900 mbar"}
  </pre>
</body>
</html>

I’ve tried to create a Thing with the HTTP Binding and then a channel and an item via the GUI. Code looks as follows:

UID: http:url:31c960574b
label: Syr SafeTech Connect
thingTypeUID: http:url
configuration:
  authMode: BASIC
  ignoreSSLErrors: false
  baseURL: http://192.168.20.18:5333/safe-tec/
  delay: 0
  stateMethod: GET
  refresh: 30
  commandMethod: GET
  contentType: application/json
  timeout: 3000
  bufferSize: 2048
channels:
  - id: SyrWaterPressure
    channelTypeUID: http:number
    label: Water Pressure
    description: ""
    configuration:
      mode: READONLY
      stateExtension: get/BAR

What am I doing wrong here?

Thanks,
Klayman

2

The result you have shown is JSON wrapped in XML.

What do your logs say?

3

The logs are rather quiet. I now changed the channel type to String just to see if any data arrives. Seems to work, now I get {“getBAR”:“4800 mbar”} as the value of my item. How can I parse this now into a numerical value of 4.80? This is how my code looks like:

UID: http:url:e6162a0ae4
label: Syr SafeTech Connect
thingTypeUID: http:url
configuration:
  authMode: BASIC
  ignoreSSLErrors: true
  baseURL: http://192.168.20.18:5333/safe-tec/
  delay: 0
  stateMethod: GET
  refresh: 3
  commandMethod: GET
  timeout: 3000
  bufferSize: 2048
channels:
  - id: SyrPressure
    channelTypeUID: http:string
    label: Water Pressure
    description: ""
    configuration:
      mode: READONLY
      stateExtension: get/BAR

Thank you!

4

Step one is to extract the 4800 mbar

Install the JSONPATH Transformation Service, then add

stateTransformation: JSONPATH:$.getBAR

to your Thing Channel configuration.

Your Item should now contain 4800 mbar after the next update/refresh.

5

Done, now it shows 4900 mbar. What next, how can I strip the mbar and divide by 1000?

6

REGEX:(.*BAR":"([0-9]+).*)∩JS:(| parseFloat(input) / 1000)
(install REGEX and JS transformations) might work (untested).

7

You could leave it, define your Item as a Number:Pressure and set the state description pattern on the Item as %.0f µbar. OH will do the conversion in units for you.

8

Ok, I now defined the item as Number:pressure and applied “%.0f µbar” as a pattern

value: " "
config:
  pattern: "%.0f µbar"
  readOnly: true

It now shows “4900 µbar” but when I click on Analyze, there is no data in the diagram…

9

I think I found it: Because I changed the item from string to float, the persistence cannot work with the new data format under the same item. Unfortunately I don’t know how to delete old data fields from influxdb, even if I delete the item itself and recreate it under the same name, the error remains…

10

I haven’t used InfluxDB in some time but I do know they have excellent docs.

11

Answer to self: Log on to linux console, start influxdb and then issue “drop measurement itemname”

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