Archive for August, 2016

Serving Assets with Selectors

12.08.2016
Ben Zahler

In a project, we recently had the requirement to serve assets with a selector. The reason for adding the selector was that all CUG protected assets need to be served from an specific dispatcher farm.

Unfortunately, the extension of assets is part of the node name in AEM. A sample geometrixx asset is stored as node “GeoCube_Datasheet.pdf” under /content/dam/geometrixx/documents .

When we try to access this with a selector /content/dam/geometrixx/documents/GeoCube_Datasheet.secure.pdf, the resource cannot be resolved, resulting in a 404.

After checking the Sling source code, we’ve found a way to get to the document with the selector: add all the selectors after the extension, and then add extension .res.

Why? that’s quite complicated:

  • adding the selectors after the original extension makes sure that the resource is actually found during resource resolution
  • rendering of resources needs to be done by the org.apache.sling.servlets.get.impl.helpers.StreamRendererServlet, but the servlet only accepts resources without an extension or with .res

But our troubles are not quite over yet: If we render this as a .res resource, Apache will serve this as content type application/x‐dtbresource+xml

The following rewrite rule should take care of that for pdf documents:

With this rewrite rule, the asset is actually available for end users at the desired url /content/dam/geometrixx/documents/GeoCube_Datasheet.secure.pdf, hiding the .res extension workaround from the end user.