Specifies the logon name used to establish the connection. This property is used in conjunction with the ij.password property to authenticate a connection. If authentication is not active then these properties are ignored.
When a username is supplied you need to be aware of the database schema. When you connect using ij.user, the default database schema applied to all SQL statements is the same as the user id provided even if the schema does not exist. Use the SET SCHEMA statement to change the default when the schema does not match the username. Alternately you can fully qualify the database objects referred to in the SQL statements . If no user is specified, no SET SCHEMA statement has been issued, or SQL statements do not include the schema name, all database objects are assumed to be under the APP schema.
java -Dij.user=me -Dij.password=mine org.apache.derby.tools.ij ij version 10.8 ij> connect 'jdbc:derby:sampleDB'; ij> set schema finance; ij> select * from accounts;