Developing Sudoku program in web application

I am working on a case study to develop a sudoku program in java web application.I am confused with the approach to follow for it.Can any body help to clear questions.

1. How i can filled some valid cells with numbers in sections so user can get a flow to fill sudoku. Is there any inbuild API available?


2. Once display sudoku game in web application which approach is good to go for allow user to fill it?

Appreciating you comments...