[jira] [Created] (SLING-6559) Sling is hiding / ignoring Parameter / Query String changes from Filters ahead of Sling

["Andreas Schaefer (JIRA)" <ji...@apache.org>]

Andreas Schaefer created SLING-6559:
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             Summary: Sling is hiding / ignoring Parameter / Query String changes from Filters ahead of Sling
                 Key: SLING-6559
                 URL: https://issues.apache.org/jira/browse/SLING-6559
             Project: Sling
          Issue Type: Bug
          Components: Engine
         Environment: Sling 9, JDK 1.8
            Reporter: Andreas Schaefer
         Attachments: ticket-sling-parameter-problem-example.zip

Any changes to parameters or the query string in a Servlet Filter ahead of Sling (before Sling Main Servlet) are ignore in Sling due to the usage of the Parameter Support class.

This means that any such filter will not receive the parameters in the request, cannot wrap the request and add, change or delete them and cannot change the query string.

I attached a sample project that will showcase that (see the ReadMe.markdown) file in the root folder. The project can be built with **mvn clean install** and if Composum is installed and whitelisted you can auto deploy it with (mvn clean install -P auto-deploy-all.

I know this is an edge case but I had at least two clients in the last two years
that required to change parmaeters and / or query strings before the Sling resource
is resolved.

But even without that Sling based on javax.servlet specification should adhere to
that and with it support and respect filters and their changes.

The reason why this goes wrong is that the Parameter Support is created during the
authentication phase way ahead of "regular" filters and with it the parameters
are fixed into place.

For a client I created a fixe by intercepting the getAttribute() for the Parameter
Support attribute and return null to create a new Parameter Support instance. To
make this work I had to read out all parameters from the original Parameter Support
instance to carry them over as well as set the flag for additional parameters.
This is working in AEM 6.2 SP1 but this is for sure not a good and generic solution.



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