The document provides an overview of Apache Sling, a REST-based web framework that utilizes a JCR content repository and is designed for content-driven applications. It details Sling's unique resource resolution approach, its features, and a demo project for creating a blog using Sling, including setup instructions and development steps. The document also highlights the scripting capabilities within Sling and includes various development considerations and challenges.

1. Content-Centric Web Development with
Apache Sling
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07/09/2017
Koen Van Eeghem

2. Who am I?
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3. Copyright © Capgemini 2017. All Rights Reserved
Koen Van Eeghem
DCX Consultant @ Capgemini - Atlas Copco Project since 09/2016
cown_ cown_ koenvaneeghem koen.van-eeghem@capgemini.com
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4. Copyright © Capgemini 2017. All Rights Reserved
Planning
• What is Apache Sling?
• What makes Sling unique?
• Demo: Blog
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5. What is Apache Sling?
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6. Copyright © Capgemini 2017. All Rights Reserved
What is Apache Sling?
• REST based web framework
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7. Copyright © Capgemini 2017. All Rights Reserved
What is Apache Sling?
• Content-driven, using a JCR1
content repository
• Implementation of the JSR 170 / 283 standard
• “best of both worlds”
• Hierarchically structured storage (node structure)
• Queryable
• != Content Management System
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1 More on JCR: http://jackrabbit.apache.org/jcr/jcr-api.html

8. Copyright © Capgemini 2017. All Rights Reserved
What is Apache Sling?
• Content-driven, using a JCR1
content repository
• Implementation of the JSR 170 / 283 standard
• “best of both worlds”
• Hierarchically structured storage (node structure)
• Queryable
• != Content Management System
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1 More on JCR: http://jackrabbit.apache.org/jcr/jcr-api.html

9. Copyright © Capgemini 2017. All Rights Reserved
What is Apache Sling?
• Powered by OSGi2
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2 More on OSGi: https://www.osgi.org/developer/architecture

10. Copyright © Capgemini 2017. All Rights Reserved
What is Apache Sling?
• Scripting inside, multiple languages (JSP, ESP, Scala, etc.)
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What is Apache Sling?
• Apache Open Source project (since 2007)
• Originally developed by “Day Software”
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12. What makes Sling unique?
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13. Copyright © Capgemini 2017. All Rights Reserved
What makes Sling unique?
• “normal” frameworks resolve a servlet from the URL then try to load data
• localhost:8080/hello?name=Koen
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14. Copyright © Capgemini 2017. All Rights Reserved
What makes Sling unique?
• Sling resolves a resource from the URL and renders it based on parameters
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15. Copyright © Capgemini 2017. All Rights Reserved
What makes Sling unique?
• Sling resolves a resource from the URL and renders it based on parameters
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16. Copyright © Capgemini 2017. All Rights Reserved
What makes Sling unique?
• Sling resolves a resource from the URL and renders it based on parameters
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17. Copyright © Capgemini 2017. All Rights Reserved
What makes Sling unique?
• Sling models map a JCR node to a POJO
• Servlets can be defined on a certain resource or on a certain path
• Useful info can be provided by selectors
• Templates can be defined in multiple languages: HTL, JSP, ESP, …
• Html Templating Language (HTL1): easy binding between Java and front-end
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1 More on HTL: https://sling.apache.org/documentation/bundles/scripting/scripting-htl.html

18. Demo: Blog
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Demo: Blog
• Basic blog with blogposts
• Sling Model for rendering blog posts
• Sling Servlet for returning a JSON list of blog posts without content
• All code can be found on GitHub
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20. Copyright © Capgemini 2017. All Rights Reserved
Demo: Blog - Part 1; setting up your environment
• Download the Sling launchpad
• Start up the launchpad:
java -jar org.apache.sling.launchpad-9.jar
• localhost:8080/system/console/bundles
• Default credentials: admin / admin
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Demo: Blog - Part 1; Setting up your environment
• Generate a maven project: sling-bundle-archetype
• Delete whatever Java classes that were automatically created
• Create a run configuration to deploy your bundle:
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Demo: Blog - Part 2; Developing your bundle
• Create a folder for your models and a folder for your services
• Update your POM
• Specify the models’ location: <Sling-Model-Packages>
• Add the dependencies to use Sling Models:
• org.apache.sling.bnd.models
• org.apache.sling.models.api
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Demo: Blog - Part 2; Developing your bundle
• BlogPostModel.java
• @Model(adaptables = Resource.class): shows we’re mapping a resource
• @Inject: injected at runtime from the JCR resource
• @Optional: is not required for a “successful” instantiation
• @Named: has another name than the Java variable
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Demo: Blog - Part 3; Developing your HTL Template
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Demo: Blog - Part 4; Create some sample content
• 3 ways of administering content on your server:
1. WebDav client: good overview, limited options
2. HTTP methods: no feedback, but you can view/add
3. Deploy files: good overview and you can view/add
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Demo: Blog - Part 5; Extending your bundle with a servlet
• GetAllPostsServlet.java
• @SlingServlet(resourceTypes = "capgemini/blog", methods =
"GET", extensions = “json")
• extends SlingSafeMethodsServlet
• uses BlogPostService.java for getting projects
• uses Gson to return JSON (excludeFieldsWithoutExposeAnnotation())
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/content/blog.json

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Demo: Blog - Part 6; Some final challenges
• Some articles were originally published somewhere else
→ add this in the model and template
• A customer wants webpages with “inspirational quotes” in a specific color
→ create a model and template for this
• A customer wants to be able to get the 3 most recent articles, with or without
details
→ adjust the JSON servlet to enable this with selectors
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28. Thanks for your attention!
Questions?
25Don’t want to ask your question for the group? Just e-mail it to koen.van-eeghem@capgemini.com and i’ll be happy to reply!