JPA AttributeConverter works unexpectedly

[Francois Green]

I've implemented an AttributeConverter which works but seems that it shouldn't.   By adding the convert annotation to the target attribute, without specifying a converter class, the attribute converter just works.

shared abstract class Role(String role) of host | guest {
  string => role;
}
shared object host extends Role("HOST") {}
shared object guest extends Role("GUEST") {}

entity
shared class Person(firstname, lastname, middle, role) {
 
  id generated { strategy = auto; }
  shared Int? id = null;
  shared variable String firstname;
  shared variable String lastname;
  shared variable String middle;
  convert//NOTE: Converter not specified
  shared variable Role role;
}

converter//NOTE: autoApply not set and should false
shared class RoleConverter() satisfies AttributeConverter<Role, JString> {
 
  convertToDatabaseColumn(Role role) => javaString(role.string);
 
  convertToEntityAttribute(JString string) => if (string == "HOST") then host else guest;
}

At least none of the documentation I've read shows anything similar in Java.  While I'm happy with the behavior, as trying to follow the Java EE 7 documentation only yielded errors, I want know if it's correct and I can rely on it.

I'm using Ceylon 1.2.2 with EclipseLink 2.6.2

[Gavin King]

Sounds like an EclipseLink question to me.

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[Francois Green]

You're right!  I recreated the project in Java and got the same behavior.  In fact, the basic string conversion works with this:

converter

shared class RoleConverter() satisfies AttributeConverter<Role, JString> {


 
  convertToDatabaseColumn(Role role) => nothing;
 
  convertToEntityAttribute(JString string) => nothing;
}


I can't find any documentation on this feature, but it seems to be a part of JPA 2.1.  Thanks for putting me on the right track.