# Building ELK

ELK is built using Apache Maven in conjunction with Tycho to tell Maven how to build Eclipse projects. There are two parts that can be built: the Eclipse Layout Kernel itself, and the metadata compiler used by the main ELK build. The remainder of this page assumes that you have opened a shell in the `build/` directory inside your clone of the ELK repository.

Note: We have had reports of people not being able to build ELK with Maven 3.3.9. We are building with Maven 3.0.5, so please try downgrading if you experience build problems where classes cannot be found although they are quite obviously there.

## The Main Build Process

Execute Maven using the following command line (note that the command line is split in order to improve readability):

    mvn
        --define elkMeta.repositoryUrl=META_REPOSITORY_URL
        clean
        ADDITIONAL_PHASES

`clean` is not strictly necessary.

For `META_REPOSITORY_URL`, insert the URL of the Maven repository where the ELK Metadata compiler can be found. If you have not touched the thing (if in doubt, this is the case), the Downloads section will tell you which repository to use to build different releases (to build the current development version, use the nightly build repository). If you have touched the metadata compiler, the repository URL should be the same as in the metadata compiler build (see below).

For `ADDITIONAL_PHASES`, the following are typical choices:

Phase | Description
--- | ---
`package` | Simply compile everything. You will find the result in the update site placed in the `org.eclipse.elk.repository/target/` directory.
`verify` | Compile ELK and execute the unit tests.

## Building the Metadata Compiler

Execute Maven using the following command line (note that the command line is split in order to improve readability):

    mvn
        -P elk-meta
        --define elkMeta.repositoryUrl=META_REPOSITORY_URL
        --define elkMeta.publishUrl=META_REPOSITORY_URL
        clean
        ADDITIONAL_PHASES

`clean` is not strictly necessary.

Maven will build a Maven repository that can be used by the main build to compile `.elkm` files. For `META_REPOSITORY_URL`, insert the URL where you want that repository to be placed. If you’re building locally, this should be a path on your local file system. For example:

    --define elkMeta.repositoryUrl=file:///home/user/elkmetarepository
    --define elkMeta.publishUrl=file:///home/user/elkmetarepository

For `ADDITIONAL_PHASES`, the following are typical choices:

Phase | Description
--- | ---
`deploy` | Compile the metadata compiler and put it into a Maven repository at `META_REPOSITORY_URL`.

## Building the Documentation

The documentation website is our source of documentation. The main build can be configured to generate the reference documentation which is part of the website from our metadata files. To do so, add the following command-line argument to the main build call:

    --define elk.metadata.documentation.outputPath=/path/to/docs/folder

The documentation website itself is built with Hugo, a static website generator. The website is setup in a way to be browsable both online and offline. To actually build the documentation website, go to the repository’s `docs/` folder and simply execute the following command:

    hugo

To edit the website, start a Hugo server instance in the repository’s `docs/` folder:

    hugo server

You can then direct your browser to `http://localhost:1313/elk/`. As you edit the website’s files and save them, the browser’s content is dynamically updated.

- Tool Developers
- Graph Data Structure
- Coordinate System
- Layout Options
- JSON Format
- ELK Text Format
- Using Algorithms Directly
- Using Plain Java Layout
- Using Eclipse Layout
- Connecting to ELK
- Advanced Configuration
- Layout View Support
- Dependency Injection
- Algorithm Developers
- Getting Eclipse Ready
- Creating a New Project
- ELK Metadata Language
- Automatic Builds
- Algorithm Implementation
- Structuring Algorithms
- Algorithm Debugging
- Unit Tests
- ELK Contributors
- Development Setup
- Development Workflow
- Installing With Oomph
- Building ELK