I\'m aware that hibernate recently redid its type system in 3.6. I think this now allows you do associate a java Class with a Type (or UserType). For example I use joda-ti
Answering my own question.
Simple enough when you know how.
configuration.getTypeResolver().registerTypeOverride( LocalDateTimeType.TYPE, new String[]{ LocalDateTime.class.getName() } );
configuration.getTypeResolver().registerTypeOverride( LocalDateType.TYPE, new String[]{ LocalDate.class.getName() } );
The TypeResolver lookups for unknown types use the class name so registering the full name of the class as the registrationKey does the job.