Many Databases do not natively support the SQL-99 BOOLEAN datatype. Boolean and boolean fields in JPA entities will thus get represented as another type in the database. OpenJPA currently has a hardcoded mapping to int 1/0 in the base DBDictionary.
But many existing databases don't use NUMBER(1) as column type but e.g. CHAR(1) (because it uses less space in the index).
There are also all sorts of possible representations where one of those is usually consistently used throughout a customer application:
- Native Boolean -> PreparedStatement#setBoolean
- Int 0/1 -> PreparedStatement#setInt
- String "Y"/"N" -> PreparedStatement#setString
- String "T"/"F" -> PreparedStatement#setString
- String "y"/"n" -> PreparedStatement#setString
- String "t"/"f" -> PreparedStatement#setString
And I've also seen translated ones: "J"/"N" in german apps for "Ja"/ "Nein" (yes/no).
So it should be possible to even add your own custom BooleanRepresentation.