Typical Java applications involve access to a database system. Database systems store data according to their type system, even object-oriented databases generally have their own storage structures. It is therefore necessary to convert Java objects as they are stored in a database, and to re-convert them when they are read. Ideally, this should be done behind the scenes by a support package. Our paper presents an approach that automates the conversion process without involving pre- or post-processing of Java code: we use a reflection mechanism, where Java code is inspected at run-time and changed to include the convert and re-convert effort. The result is a flexible and transparent Java database access.