posted 20 years ago
There are many other ways of connecting to databases, but they all need extra work, and all are specific to particular databases or database interfaces. For example, you could implement Oracle's SQL.NET protocol yourself, rather thna using Oracle's thin drivers, or write code to parse the data structures in an Access MDB file. You would need to deal with threading issues and data integrity yourself, but it could theoretically be done.
When JDBC is so easily available, powerful, and implemented for such a wide range of databases there seems little reason other than personal interest to do any of this, though. If you are interested in this sort of thing, there is a book "Java Database Programming" by Brian Jepson, published by Wiley, which describes in detail the implementation of an SQL database which uses plain text files for data storage, and includes all the source code.