JavaDB/Derby is sensitive if using a JDBC driver that is not compatible with the database (server) engine. If there is an incompatibility strange errors and exception will appear in DbVisualizer. When connecting to JavaDB/Derby make sure the major and minor versions for both the database and JDBC driver are the same. In the following both are 10.12 which is fine:

Apache Derby - (1704137)
Apache Derby Embedded JDBC Driver - (1704137)

If there is a difference such as the following (10.10 vs. 10.12), problems may most likely occur while using DbVisualizer:

Apache Derby - (1458268)
Apache Derby Network Client JDBC Driver - (1704137)

To fix this:

  1. Open Tools->Driver Manager in DbVisualizer
  2. Select the corresponding JavaDB/Derby driver entry in the list
  3. Duplicate (Driver->Duplicate Driver) the selected driver to a custom driver
  4. Set a unique name on the custom driver
  5. In the User Specified tab, remove the jar files and load the following files from the database installation: derby.jar, derbyclient.jar, derbynet,jar
  6. In the Connection setup for your database connection, select the new custom driver entry in the Driver (JDBC) drop-down
  7. Connect and verify the versions in the Connection Message text box