I want to obtain the current base url of an application which usually
What version of Play Framework are you using ?
If you are using Play 1.x, you should manually specify the base url of your application using an application.conf variable. This is the way I do in order to retrieve base url for my applications. For example :
application.baseUrl=http://localhost:9000 %devcloud.application.baseUrl=http://dev-url.com %prod.application.baseUrl=http://prod-url.com
With Play Framework 2.x, you could use additional configuration file (thus variables values depending on the environment - prod, dev, test ...), as explained here : http://www.playframework.com/documentation/2.2.x/ProductionConfiguration
These solutions work especially if you do not want to depend on an Action or a Controller. Else, you can retrieve the absolute URL using the Request within the Action.