Coding Guidelines

1. General

  • The OpenEMS Coding Guidelines are based on (and complement) the Java Coding Convention.

  • Limit pull requests to a small and closed topic.

2. OpenEMS Edge & Backend

2.1. Java Code

  • Limit Pull-Request to only one bundle/directory preferred

  • Remove unnecessary console.logs

  • Remove unnecessary empty lines

  • Never use System.out.println()

  • Fix all errors & warnings

  • Use precise naming for methods/functions

  • Use narrow scopes for variables; avoid class variables

  • Split code in Interface, Implementation(..Impl) and Config files

  • Use modern Java 21 syntax (e.g. 'var' keyword, streams, etc.)

  • Add readme.adoc to a new bundle

  • Review data in bnd.bnd file

  • Format all files via Eclipse Autoformat, organize Imports, apply Checkstyle suggestions (see below)

  • Avoid unnecessary comments on self explaining code

  • Add comments to code that is difficult to understand

  • Prefer functional programming (e.g. use Lambda expressions)

  • Add JUnit tests.

  • Run ./tools/prepare-commit.sh script

2.2. Tool support

While IntelliJ also works, Eclipse IDE is the officially supported development environment. It also provides tool support for guided assistance via bndtools.

Eclipse Version

Some Eclipse default code formatting rules and warning settings change over time. Therefore, always use the latest Version of the Eclipse IDE for Java Developers (4.30.0 +).

Eclipse Code formatter

Use Eclipse [built-in] code formatting rules

  • Eclipse → Window → Preferences → Java → Code Style → Formatter → ActiveProfile → select → Eclipse [built-in]

Before you commit files, run the Eclipse code formatter on each java source code file (Ctrl + Shift + F).

Eclipse Checkstyle plugin

Use Eclipse checkstyle plugin Eclipse-cs. Install it with

  • Eclipse → Help → Eclipse Marketplace → Find → Eclipse-cs → Install

Configure it with

  • Eclipse → Window → Preferences → Checkstyle → New →

    • Type: Project Relative Configuration

    • Name: OpenEMS

    • Location: /cnf/checkstyle.xml

Later set OpenEMS as default. Enable Checkstyle for every bundle you like in the Bndtools Explorer in the bundles context menu.

3. OpenEMS UI

3.1. TypeScript

  • Act according to the rules above wherever it makes sense to do so.

4. Git-Flow workflow

  • OpenEMS development follows the Git-Flow workflow.

  • Choose precise naming of pull request and its comments when making a pull request

  • After opening the Pull-Request, review for yourself the actual changes line by line in the 'files' tab on Github. Ask for review only after you checked the actual changes again this way.

  • Ask for review when pull request is ready for review (not before)

Note: If you realize, that you added files accidentally, you can always reset them to the current 'develop' state with the command git checkout develop <filename>