Apache Sling Starter Application

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Apache Sling

Build Status Test Status Sonarcloud Status JavaDoc Maven Central License

Apache Sling Starter

This module is part of the Apache Sling project.

The starter project produces feature artifacts that can be launched using the Feature Launcher.

It is not meant to be a production-ready setup, more as a way to facilitate experimenting and learning Sling.

See Releasing a new version of the Sling starter for how to create a release of this module.

How to run the Sling Starter module in Standalone mode

Note This is a note “mvn clean” deletes the “launcher” work directory in the project base directory. It is advisable to use a work directory outside of the project directory.

  1. Build the Sling Starter using

    mvn clean install

    in the current directory.

    Hint You can defer stopping the instance after running the ITs with argument -Dfeature-launcher.waitForInput=true to do some manual checks.

  2. Start Sling backed by

    • Oak SegmentStore with
      target/dependency/org.apache.sling.feature.launcher/bin/launcher -f target/slingfeature-tmp/feature-oak_tar.json
    • Oak MongoDB DocumentStore with
      target/dependency/org.apache.sling.feature.launcher/bin/launcher -f target/slingfeature-tmp/feature-oak_mongo.json
      This expects a MongoDB server to be running, search for mongodb:// in the feature files for the expected URL (currently mongodb://localhost:27017).
  3. Browse Sling in localhost:8080

How to run the Sling Starter Docker image

The following tags are supported

Tag nameSupported platformsLinks
12, latestamd64Dockerfile, Release notes
11amd64Dockerfile, Release notes
10amd64Dockerfile, Release notes
9amd64Dockerfile, Release notes
snapshotamd64, arm64Dockerfile
  1. Start Sling Docker image backed by
    • Oak SegmentStore with
      docker volume create sling-launcher
      docker run --rm -p 8080:8080 -v sling-launcher:/opt/sling/launcher apache/sling:snapshot
    • Oak MongoDB DocumentStore with
      docker volume create sling-launcher
      docker run --rm -p 27017:27017 mongo:4.4.6
      docker run --rm -p 8081:8080 -v sling-launcher:/opt/sling/launcher apache/sling:snapshot oak_mongo

The docker/ directory contains sample files related to container-based development.


The Sling Starter will execute two suites of tests using the maven-surefire-plugin:

  1. A small set of smoke tests, embedded in the project, that verify the basic functionality of the Starter
  2. An extensive set of end-to-end tests that verify the overall functionality of the Starter and the bundles that are embedded into it

By default, these are both executed when building the project against an Oak SegmentNodeStore backend.

Additionally, when the ci profile is enabled the smoke tests are also executed in against an Oak DocumentNodeStore backend. For technical resons, the full end-to-end tests are not executed.


The Sling Starter Docker image is only for testing/learning purposes. For your custom applications, please configure your Feature model and build your image with all dependencies and configurations built in.

Our example Docker image uses /opt/sling/bin/launch.sh script as the entrypoint. It supports the following environment variables:

Environment variableDescriptionExample
JAVA_DEBUG_PORTRun Sling Starter in Java debug mode5005
EXTRA_JAVA_OPTSExtra java options e.g Xmx or Xms.-Xms256m -Xmx2048m

Example running Sling Starter in debug mode with custom memory settings

docker run -p 8080:8080 -p 5005:5005 -e JAVA_DEBUG_PORT=5005 -e EXTRA_JAVA_OPTS='-Xms256m -Xmx2048m' apache/sling:snapshot

Building the Docker image

This module can optionally build a Docker image. This is achieved by running a build with the -Ddocker.skip=false argument. By default, the image is built as apache/sling:snapshot. The tag can be overrriden using the docker.image.tag Maven property.

$ mvn clean package -Ddocker.skip=false -Ddocker.image.tag=local
$ docker run --rm -p 8080:8080 apache/sling:local

Extending the Sling Starter

If you wish the extend the Sling Starter but would like to keep various application-level features out, you can start with the nosample_base aggregate, which contains:

  • all the base features
  • Oak base features, without the NodeStore setup
  • No applications ( Composum, Slingshot, etc )

For instance, launching an empty Sling Starter with segment persistence can be achieved by running

target/dependency/org.apache.sling.feature.launcher/bin/launcher -f target/slingfeature-tmp/feature-nosample_base.json,target/slingfeature-tmp/feature-oak_persistence_sns.json

Your own feature files can be added to the feature list.

Helper scripts

The scripts directory contains helper scripts that will aid with local development by simplifying the use of tools external to the Sling Starter.