What is the purpose behind building of Apache Sling, Felix, Jackrabbit projects

Question

I am asking a very basic question here.

Question is

I am using Apache Sling , Apache Jackrabbit, Apache Felix in my project as said by my in

Answer 1

I had the same doubts. The best response I was able to find is in the official Sling page (https://sling.apache.org/)

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(What is) Apache Sling, in a hundred words:

Apache Sling is a web framework that uses a Java Content Repository, such as Apache Jackrabbit, to store and manage content.

Sling applications use either scripts or Java servlets, selected based on simple name conventions, to process HTTP requests in a RESTful way.

The embedded Apache Felix OSGi framework and console provide a dynamic runtime environment, where code and content bundles can be loaded, unloaded and reconfigured at runtime.

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So, resuming it:

• Sling is a web framework --> using jackrabbit --> based/supported on JCR API.
• You can see Apache Felix like a container with its manager.

Note that Sling started as an internal project at Day Software. It's the reason why some bundles/libraries are named like com.day, but in the ends they are two names for the same.

Also, if you want to be clear about Jackrabbit and JCR API you can visit the Jackrabbit's official page http://jackrabbit.apache.org/jcr/jackrabbit-architecture.html