So how do we get from all those bundles to something that actually starts, creates a repository and listens to incoming HTTP requests?

While it is possible to deploy a Sling Web Application Archive (.war) file on any Servlet Container like Tomcat, that's not what we do here.

Instead it's a standalone Java application. Prior to Sling 12 an executable launchpad.jar was created with the 'provisioning model'. Now, the Sling OSGi Feature Model combines bundles, settings, content, and setup scripts into a single unit called a Sling-Feature. The corresponding Maven Plugin checks if all dependencies are fulfilled. It then creates feature files in JSON format or feature-archive files (.far), which are started using the feature-launcher. Although you could package everything into a single executable uber-jar (with the kickstarter), we instead build a Docker image directly..

Initially I went with a fork of the Sling Starter in order to add more features (Peregrine CMS) here in src/main/features/app into a working launcher. I later found that the starter project provides a new type of build output called 'osgifeature'. It's basically json with maven coordinates to bundle-jars and content-zips plus repo-init scripts.

Let's say you already have a Sling running inside a docker container on the internet. In a corporate environment that is probably more of an organizational issue to be honest.

Now someone has quickly vibe-coded a TypeScript app, reaching the famous 80% completion, and you want to demonstrate it on your mobile device during lunch. The app comes as a zip-file containing an index.html and the rest is compressed JavaScript. You extract the files into a content package project and install it  via package-manager. Done.

^{Well, almost. The URL might be cumbersome, and the app may be designed to run without a context path. For example, a path like /apps/playground/my-awesome-app/index.html might not function correctly..We have not yet discussed reverse proxy and caching solutions like Apache, Nginx, or Traefik.}

Alternatively, if you have HTML and CSS and want a templating solution other than PHP, review the reverse CSS Zen Garden example to see how it is implemented.. _{We need a link to a beginner's-guide here.}

Or you have a react/angular/vue app running somewhere else, that needs a content/business API? Sling Models Exporter is your friend. Or any combination of the above, Sling does not really enforce an architecture.

This approach of combining a single-page application with a content API is now known as a "Headless CMS". Sling was one before it was cool. Downside is, the lack of a polished user interface may be why it has not been widely adopted.

Finally let's add the Composum-Pages CMS. The page you're currently reading is made with it.

It might seem insane to run two CMSs in the same Docker image. I mean learning one is already a task. But it makes a point about the architecture of Sling! The fact that this is even possible is both logical and surprising.

Unlike nodes-browser/package-manager/user-manager explained above, it's not part of the official Sling Starter. Instead there is an official Sling CMS, but that is not used here, three would be really silly.

Again it has it's own WYSIWYG editor, too many OOTB components, asset-management and publishing concept. Publishing involves copying content nodes from the '/content' path to the '/public' path within the JCR repository. It would also support publisher-author distribution.

We're also just running the default theme here. The look and feel isn't as nice a Peregrine's default-theme and the mobile-view lacks some responsiveness.

However, the default appearance may not reflect its full capabilities, it's probably made by backend developers. The aim would actually be to explore further and to come up with an own app on top, with custom html and own components in the future.

When generative AI came along, out of the need for a logo it was given the silly task to create an image of a "Two Headed Sling". That was the result.

AI has evolved, so have the prompts. Here is an inspiration, in case you feel to evolve that style.

A photo-realistic image of a two-headed sling catapult launching a laptop, set in a clean and organized, steampunk-styled laboratory. The catapult is the primary focus. A jackrabbit is present. Three signs are present in the background with the words Sling, Jackrabbit, and Content. The lighting is dominated by a blue hue.

Create a humorous, 16x9 image of a two-headed sling catapult launching a laptop in a laboratory setting. The artistic style is cyberpunk and "the matrix". A cute, white jackrabbit is present. Three signs are in the background with the words "Sling" "Jackrabbit" and "Content". The lighting has a dominant blue hue; the catapult and laptop are the primary focus.