Typed queries and fetch plans

Reified APIs

findAs<T>, createQueryAs<R>, createSelectionQueryAs<R>, createNamedQueryAs<R>, and createNativeQueryAs<R> remove repeated T::class.java arguments. Hibernate still validates the query text and result mapping.

val books = sessionFactory.withSessionSuspending { session ->
    session.createSelectionQueryAs<Book>(
        "select b from Book b left join fetch b.author"
    ).resultList.awaitSuspending()
}

The tests show findAs returning null for an unknown ID. getReferenceAs may return a proxy immediately, and reading its ID does not imply a database lookup. Initializing other properties still requires a live session and row.

Mutiny and Stage differences

Do not assume that the two packages are identical from their common function names.

• Mutiny Session supports Hibernate LockMode, JPA LockModeType, multiple IDs, natural IDs, EntityGraphs, and graph-name lookup.
• Stage Session supports Hibernate LockMode, multiple IDs, and natural IDs, but has no LockModeType or EntityGraph findAs overload.
• Mutiny StatelessSession likewise has more getAs overloads than Stage.

Fetching lazy associations

Book.author and Author.books in the tests are lazy associations. Resolve required relationships inside the session using one of these approaches:

1. an HQL fetch join;
2. an enabled @FetchProfile;
3. createEntityGraphAs or the named Book.withAuthor graph;
4. explicit Hibernate Reactive fetch().

The Criteria examples use generated JPA metamodel types Author_ and Book_, not Querydsl. The module build deliberately selects the metamodel generator.

Native query and mapping

The type argument to createNativeQueryAs<R> does not guarantee that arbitrary SQL results match R. State whether the result is a scalar, entity, or registered result-set mapping and verify it against the actual database. The AffectedEntities overload supplies synchronization hints for native queries and the persistence context.

Executable evidence

• Mutiny query extensions
• Stage query extensions
• Book.kt
• MutinySessionSupportTest.kt
• StageSessionSupportTest.kt