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 may 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 version 10.12 which is fine:

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

If there is a difference such as the following (version 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 in DbVisualizer 13.0 and later

The template driver for Derby includes Maven Artifacts, you can change the version in the Maven editor and download the new version as described the new Driver Manger.

To fix this in previous version of DbVisualizer:

  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