You can create a regular spring bean exposing a method which loads the data you require from the database and stores it in your map. Annotate this method with @PostConstruct and spring will ensure that it is called when your application context starts, hence loading your map.
You could use springs JdbcTemplate to load your data within this method
See Spring PostConstruct doco for information on the @PostConstruct annotation
See JdbcTemplate doco for information on JdbcTemplate