Hi Rajiv,
mentioned method sets only genIL attribute properties. Those are used for display options in the UI only. They do NOT include an actual check whether you've entered something or not!
Options:
1) You could use the generic web dynpro checks (see UIBB customizing, there's a flag for "check mandatory fields").
2) Implement specific validation as described by SAP note 2308424.
Recommendation:
Go for 2) although this means more effort. The benefit surely is that 2) is always executed in all places that shall check BP data (meaning: not only in SOM UI, but in DIF, data replication, and so on).
Cheers
Michael