Platform information: Hardware: Windows 10 Laptop OS: Windows 10 Java Runtime Environment: Zulu Java 8 openHAB version: 2.5.6 I would like to create a HTML form that consists of a button, that when clicked, posts to the REST API and sets the temperature of a thermostat to 20 degrees Celcius. O…

I think most browsers will not allow you to post form data without it being in key=value format. You might need a little javascript to do what you want. If you must use an HTML form, you could post to an interim String type Item and have a rule parse out the bits you are interested in.