Jooq convert subset of selected columns to entity

Question

If I have two tables with a simple many-to-one relationship:

CREATE TABLE parent (
  id BIGINT PRIMARY KEY,
  name VARCHAR(255)
)

CREATE TABLE child (
  id BIGINT PRIMARY KEY,
  name VARCHAR(255),
  parent_id BIGINT FOREIGN KEY REFERENCES parent (id)
)

How can I query on the child table and convert the rows corresponding to the parent table to a Java Record easily with Jooq?

    var a = dslContext.select(
        PARENT.ID,
        PARENT.NAME,
        DSL.field(DSL.row(
            PARENT.child().ID,
            PARENT.child().NAME)
            .convert(???)) // How can I convert sub-entities like this?
        .fetch(Records.mapping(ChildDTO::new)); // This works fine for the top-level

It seems like something along those lines ^ should work, but I haven't been able to find it. Am I on the right track, or is there another approach I should be taking?

Answer 1

I think there's just a problem of reversed relationships here, where child and parent were confused. This should work?

dslContext
    .select(
        CHILD.ID,
        CHILD.NAME,
        row(CHILD.parent().ID, CHILD.parent().NAME).mapping(ParentDTO::new))
    .from(CHILD)
    .fetch(Records.mapping(ChildDTO::new))

THis example is using Row2.mapping(Function2), which is just convenience for an ad-hoc converter placed on the Row2 expression, which is a SelectField<Record2<T1, T2>> (there's no need to wrap it in DSL.field(...), explicitly)