AEM - Understanding the Sling Resolution Process!

AEM – Understanding the Sling Resolution Process!

March 20, 2020 satishkchoudhary@gmail.com 0 Comments

In this blog, I will explain how Sling maps URLs to a script or and servlet.

Scripts and servlets are itself resources in Sling and thus have a resource path: this is either the location in the JCR repository, the resource type in a servlet component configuration or the “virtual” bundle resource path (if a script is provided inside a bundle without being installed into the JCR repository).

Understanding Sling Resolution Process

Sling is resource oriented
Resources are maintained as Virtual tree
Resource is generally mapped to JCR node

URL ->Resource = JCR Structure

Basic Steps of Processing URL

Each Content item in JCR repository is exposed as an HTTP resource.

Decompose the URL
Search for respective Node
Resolve the Resource
Resolve Script/Servlet
Create Rendering Chain
Invoke Rendering Chain

Decomposing The URL

Lets take a sample url: http://learnaem.com/aem/slingresolution.printable.a4.html/a/b?x=true and try to decompose it. This URL can be decomposed as below:

http://learnaem.com – Protocol followed by Host name
aem/slingresolution – Content Path
.printable.a4 – Selector(s) – Alternate presentation
. html – Extension – Content Format

Lets take a sample url: http://learnaem.com/aem/slingresolution.printable.a4.html/a/b?x=true and try to decompose it.

This URL can be decomposed as below:

http://learnaem.com – Protocol followed by Host name
aem/slingresolution – Content Path
.printable.a4 – Selector(s) – Alternate presentation
. html – Extension – Content Format
a/b – Suffix – Additional information
x=true – Parameters – for dynamic content

Resolving Requests to Resources

Check if node exits at the location specified in the request

No node is found, search without file extension

If no node is found, return status code 404

If node is found, read node property to identify resource type and locate respective script to build the response

```
Respond with output
```

Locating and Rendering Scripts

Locate:

Identify the resource from the request and locate its resource type, and extract the values

Render Default, if no matching Script:

If no matching script is found, default script is rendered

Multiple Match – More selector matches the better

The script name with best match is selected

e.g. http://learnaem.com/aem/slingresolution.print.a4.html