【JPA/Querydsl】OneToManyなテーブルから必要なカラムだけDTOにマッピングする（transform,groupBy）

CREATE TABLE book (
    id VARCHAR(255) PRIMARY KEY,
    title VARCHAR(255) NOT NULL,
    author VARCHAR(255) NOT NULL,
    release_date DATETIME NOT NULL //この行は今回取得したくない！！！
);

CREATE TABLE rental (
    id VARCHAR(255) PRIMARY KEY, //この行は今回取得したくない！！！
    user_id INT NOT NULL,
    book_id VARCHAR(255) NOT NULL,
    rental_date TIMESTAMP NOT NULL,
    return_deadline DATETIME NOT NULL //この行は今回取得したくない！！！
);

import java.time.LocalDateTime
import javax.persistence.Entity
import javax.persistence.Id
import javax.persistence.JoinColumn
import javax.persistence.OneToMany
import javax.persistence.Table

@Entity
@Table(name = "book")
class BookEntity(
    @Id
    var id: String? = null,
    val title: String? = null,
    val author: String? = null,
    val releaseDate: LocalDateTime? = null,
    @OneToMany
    @JoinColumn(name = "book_id")
    val rentals: Set<RentalEntity>? = null,
)

import java.time.LocalDateTime
import javax.persistence.Entity
import javax.persistence.Id
import javax.persistence.Table

@Entity
@Table(name = "rental")
class RentalEntity(
    @Id
    var id: String? = null,
    val userId: Int? = null,
    val rentalDate: LocalDateTime? = null,
    val returnDeadline: LocalDateTime? = null,
)

data class BookWithRentalDto(
    val id: String,
    val title: String,
    val author: String,
    val rentals: List<RentalDto>
)

data class RentalDto(
    val userId: Int,
    val rentalDate: LocalDateTime,
)

import com.querydsl.core.types.Projections
import com.querydsl.jpa.impl.JPAQueryFactory
import com.sample.infra.jpa.entity.QBookEntity //自動生成されるQEntity
import com.sample.usecase.query.BookDto

val queryFactory: JPAQueryFactory  = JPAQueryFactory(entityManager); //entityManagerはjavax.persistence.EntityManager
val book = QBookEntity.bookEntity //自動生成されるQEntity
val result = queryFactory
    .from(book)
    .leftJoin(book.rentals, rental)
    .where(book.id.eq(id))
    .transform(
        groupBy(book.id).`as`(
        Projections.constructor(
            BookWithRentalDto::class.java,
            book.id,
            book.title,
            book.author,
            list(
                Projections.constructor(
                RentalDto::class.java,
                rental.userId,
                rental.rentalDate
            )
        )
        )
    )
)
val bookWithRental = result[id]