java embedded database w/ ability to store as one file

Question

I need to create a storage file format for some simple data in a tabular format, was trying to use HDF5 but have just about given up due to some issues, and I'd like to reexamine the use of embedded databases to see if they are fast enough for my application.

Is there a reputable embedded Java database out there that has the option to store data in one file? The only one I'm aware of is SQLite (Java bindings available). I tried H2 and HSQLDB but out of the box they seem to create several files, and it is highly desirable for me to have a database in one file.

edit: reasonably fast performance is important. Object storage is not; for performance concerns I only need to store integers and BLOBs. (+ some strings but nothing performance critical)

edit 2: storage data efficiency is important for larger datasets, so XML is out.

Answer 1

Nitrite Database http://www.dizitart.org/nitrite-database.html

NOsql Object (NO2 a.k.a Nitrite) database is an open source nosql embedded document store written in Java with MongoDB like API. It supports both in-memory and single file based persistent store.

Answer 2

H2 uses only one file, if you use the latest H2 build with the PAGE_STORE option. It's a new feature, so it might not be solid.