Hi mnkumar,
This problem is may be due to the fact that your view may contain null values in any of the columns specified in COMPOSITE-ID section of the configuration.
Hibernate is fetching the null records which contain null values in the composite primary key,
So two solutions,
1) Change your hbm.xml and class files to make sure that the columns specified in the composite-id will always have not-null values
or
2) Create a primary key for your view. (If you are using any tools to generate the hbm files, try running the tool after creating the primary key on the view)
you can check
http://psoug.org/reference/views.html for creating a primary key on the view.
Hope this helps.