Hi Swarup,
You will have to write code in getter method to get some value and show it on web UI. You will not be able to write anything in any database field using this approach.
If you want this field to be mapped to some database field then I recommend either of the following two approaches:
1. If it is a custom field then you should be using AET to add the field which would take care of everything.
2. If it is a standard field then you should be adding a model attribute to a custom context node