HSQLDB

HSQLDB is a pure java RDBMS which supports more SQL features than we need for xplanner.
It can be deployed in 4 modes:

1. Standalone (embedded): database runs inside client VM and is only accessible from it, i.e. no multi-user capability. Simple persistence to regular file(s) (By default one, multiple if cached tables are selected).
2. In-memory (embedded): Same as standalone but with no persistence (potentially good to speed up acceptance testing)
3. Server: runs as a regular external server process
4. Web: Runs as a web server or as a servlet in a container. Queries are submitted through http. No transaction.

Guide

Standalone mode

In the default standalone mode everything is kept in memory. In order to save everything to disk a sql shutdown must be issued before shutting the hosting VM to flush it correctly.

XPlanner usage

Use in our standalone install package

We are using the standalone mode. A tomcat instance is pre-loaded with a pre-populated hsqldb instance.

Use in our acceptance testing

Tips

Defining hibernate.connection.database seems to throw the connection settings off. The database path will become <currentpath>/hibernate.connection.database.

References

• Official HSQLDB site
• A good benchmart between embeddable java rdbms
• Unit-testing with HSQLDB
• Embedding HSQLDB for testing