Say I have an entity that contains an element collection of an embeddable type. The embeddable has an attribute that is an enumeration. I want to represent/encode values of the enumeration in the database as a single character, which is why I wrote a converter to do this. Modulo renaming of classes and attributes, the code looks like this:

@Entity
class Entity {
   // ...
   @ElementCollection
   @CollectionTable(name="entity_l", joinColumns=@JoinColumn(name="entity_id"))
   private List<Embeddable> list;
   // ...
}

@Embeddable
class Embeddable {
   @Column(nullable=false, updatable=false)
   @Convert(converter=MyEnumConverter.class)
   private MyEnum field;
}

class MyEnumConverter implements AttributeConverter<MyEnum, Character> { /*...*/ }

Using Postgres, when Hibernate creates that database schema, it will map the embeddable's field to type `integer` rather than `character(1)`.

I have also tried the following, without any difference (still `integer` used in the database):

@Entity
class Entity {
   // ...
   @ElementCollection
   @CollectionTable(name="entity_l", joinColumns=@JoinColumn(name="entity_id"))
   @Convert(attributeName = "field", converter=MyEnumConverter.class)
   // Using @Convert(attributeName = "list.field", converter=MyEnumConverter.class) neither works.
   private List<Embeddable> list;
   // ...
}

@Embeddable
class Embeddable {
   @Column(nullable=false, updatable=false)
   private MyEnum field;
}

class MyEnumConverter implements AttributeConverter<MyEnum, Character> { /*...*/ }

My first question is whether the JPA spec covers this use case. I could not find any explicit statement that this would not be allowed. In fact, the JPA Wikibook makes the following statement:

Another option, if converting a custom type, is to have the Converter applied to any mapped attribute that has that type.

As a last comment, I have other enumeration attributes in entities (rather than embeddables) where conversion to a single character works well and where the type in the database is indeed `character(1)`.