A variety of different parts of openHAB can be extended, we go through all of them.
openHAB uses git as its version control system and GitHub for hosting the different repositories and source code. You will get in contact with git in many places and it makes sense to get familiar with its basic commands and concepts. There are many pages to learn about Git. Try git - the simple guide as a start.
Add-ons and the core itself are written in Java. Java is not hard to learn, but it helps if you have a general technical understanding of programming languages.
The different guides of this chapter assume that you are somewhat familiar with Java 8 and that you have a rough idea of Git's workflow (eg "checkout", "branches", "push").
Choose the Right Concept
openHAB allows you to build up on the following concepts:
- Bindings: A binding connects to external services or devices,
- Automation engine module: A trigger, condition or action that can be used in automation rules (or scripts),
- Transformation / Profiles: Can be used to transform a Thing Channel value before it is assigned to an Item,
- an IO service: Exposes openHAB internals via a defined interface (for example the REST interface, HomeKit or Hue Emulation Service)
- a Persistence service: Persist item state updates and/or changes and allow them to be retrieved for specific points in time.
- Natural language processing skill: Executes something depending on the understood Intents and returns something back to the user,
- Audio sinks/sources: Extend where audio can be played on or implement audio sources.
- and many more (not covered yet).
Sometimes though its just not worth writing a binding and you are better off just using an http action in a rule or script to retrieve some values.
Therefore: First think what you want to archive! Check our community forum and discuss your concept.
Find the right abstraction and the corresponding link on the left navigation panel. General coding guidelines apply to all types of addon development.
Setup the Development Environment
Development can happen on any of the supported operating systems (Windows, Mac OS, Linux).
Please ensure that you have the following prerequisites installed as well:
- Git For retrieving our source code and push changes back. On Windows: Must be available in %PATH%
- Maven 3.x Our buildsystem tool. On Windows: Must be available in %PATH%
- Java JDK 8, for example from Oracle Oracle JDK 8. On Windows: %JAVA% must be set.
You can use any IDE that is suitable for OSGi/Java development. We have prepared some step-by-step guides for the following IDEs:
Not sure what to choose?: openHAB maintainers use Eclipse IDE.