Thank you for clarifying it.  You can use any HTML Parser library(eg: JSoup HTML Parser) to do that. Include that dependency in pom.xml file and then use it to read HTML content or even links on any internal page. Sample Reference code can be found here:https://mkyong.com/java/java-how-to-get-all-li...

You can write a groovy script that crawls over your /content/<site> looking for strings that start with /content. Then, use ResourceResolver to verify whether those paths exist. The following links may be helpful:a) Sample Groovy Script => https://gist.github.com/trekawek/72b3515a6641ca5f4b29b) Reso...

Can you please enable DEBUG logging for error.log loggers and see whether you get any requests for custom servlet in error.log file?

Verify the CRUD permissions for those groups in /useradmin console.Also check their ACLs in crx, if it's specific to any node.These might help figure out the reason.

You can check how your request is being processed/forwarded in /system/console/requests console. You can also check the incoming requests in request.log, access.log and the reason for failure in error.log. Also try enabling DEBUG logger for your custom servlet. That may also help. Hope these help.  ...

In addition to it, since AEM 6.4 onwards, Repository Restructuring occurred.The following doc may be helpful in finding the correct locations/paths of nodes in AEM 6.5:https://docs.adobe.com/content/help/en/experience-manager-65/deploying/restructuring/repository-restructuring.html

It is recommended to create and maintain the configuration file by making actual changes in the web console. The following doc may be helpful:https://docs.adobe.com/content/help/en/experience-manager-64/deploying/configuring/configuring-osgi.html#osgi-configuration-with-configuration-files Hope it h...

Enable DEBUG logging to error.log file on ROOT logger.Then, try to save the config, and share what you find in that log file. Moreover, what do you see in stderr.log & stdout.log files?

Try referring to the following doc:https://docs.adobe.com/content/help/en/experience-manager-learn/getting-started-wknd-tutorial-develop/project-setup.html It may be helpful.

I would also like to share the Best Practices for Querying and Indexing doc provided by Adobe. https://docs.adobe.com/content/help/en/experience-manager-64/deploying/practices/best-practices-for-queries-and-indexing.html