Parimala,
First things first. The Page Object Model pattern doesn't mandate that you have to have your locators passed in via any specific mechanism. Page Object Model merely states that you would need to visualise your actual page as a Java object and use the Java Object to interact with your page via mechanisms that the java object provides for the interaction.
The most commonly used ones by everyone which relies on PageFactory relies on annotations to pass in the locators for every element.
Sometime back I was doing some research around Page Factory and I stumbled into a mechanism using which you can decouple page factory [ which initializes page objects via reflection and helps find web elements ] and an external data source which would house the locators.