Thanks kasq !
Is there any better approach than VanityURL ?
For Information If I am using alias name for the same page then yes I am able to call the page with the alias but one more requirement is that I want to redirect to the alias URL if page requested with the original name .
If you have Apache HTTPD with dipatcher infront of your CQ you can use a Rewrite rule to redirect your SEO friendly url to the correct path in CQ.
You basically do a regex pattern matching and redirect /content/site/article_* to /content/site/article/*
You could also use the Sling mappings for resource resolution tool: http://sling.apache.org/site/mappings-for-resource-resolution.html
An example is in the following page, which is about using multiple domains used with Dispatcher, but the URL mapping applies to any context: http://dev.day.com/docs/en/cq/current/deploying/dispatcher/disp_domains.html#CQ5 Rewrites Incoming URLs
scroll down to the Configure Sling Mapping for Resource Resolution section.
if you want to display only the alias name of a page instead of the "real name", the page must be named incorrectly. Honestly, this requirement does not make any sense.
If you really want to implement it, you should add a check at the very beginning of the page and check if the name under which this resource is being displayed is the name of the alias, and redirect otherwise.