A library like Apache POI can read Excel files. Then you'd use the
JDBC API (via an appropriate driver for your DB of choice) to insert the data into the DB.
This being a web app, Access would probably not be a good choice, though - the JDBC/ODBC bridge driver is buggy, not maintained, and not thread-safe. It will also be removed from the JRE in
Java 8. A commercial driver would be a better alternative, or -of course- a proper multi-user DB like MySQL, PostgreSQL, Derby etc.