Spring supports

Spring Boot AutoConfigure

Kotlin JDSL supports Spring Boot AutoConfigure. If your project has both Spring Boot and com.linecorp.kotlin-jdsl:spring-data-jpa-support or com.linecorp.kotlin-jdsl:spring-batch-support dependencies, AutoConfiguration automatically creates the JpqlRenderContext bean.

If you declare your JpqlSerializer or JpqlIntrospector as a bean, it will be included with the JpqlRenderContext bean.

Spring Data Repository

If your JpaRepository extends KotlinJdslJpqlExecutor, you can use the extension provided by Kotlin JDSL.

interface BookRepository : JpaRepository<Book, Isbn>, KotlinJdslJpqlExecutor

val result: List<Isbn?> = bookRepository.findAll {
    select(
        path(Book::isbn),
    ).from(
        entity(Book::class),
    )
}

val result: Page<Isbn?> = bookRepository.findPage(pageable) {
    select(
        path(Book::isbn),
    ).from(
        entity(Book::class),
    )
}

val result: Slice<Isbn?> = bookRepository.findSlice(pageable) {
    select(
        path(Book::isbn),
    ).from(
        entity(Book::class),
    )
}

val result: Stream<Isbn?> = bookRepository.findStream {
    select(
        path(Book::isbn),
    ).from(
        entity(Book::class),
    )
}

If you want to use KotlinJdslJpqlExecutor in @DataJpaTest, you need to import KotlinJdslAutoConfiguration in the test. Since @DataJpaTest is a slice test, it only creates minimal beans. And the minimal bean does not include KotlinJdslAutoConfiguration. So if you want to use the features of Kotlin JDSL in @DataJpaTest, you need to import KotlinJdslAutoConfiguration directly in your test.

Spring Batch

Spring Batch provides JpaPagingItemReader and JpaCursorItemReader for querying data with JPQL. Kotlin JDSL provides KotlinJdslQueryProvider so that a JPQL query created in DSL can be executed in it.

@Auwoired
lateinit var queryProviderFactory: KotlinJdslQueryProviderFactory

val queryProvider = queryProviderFactory.create {
    select(
        path(Book::isbn)
    ).from(
        entity(Book::class),
    )
}

JpaCursorItemReaderBuilder<Isbn>()
    .entityManagerFactory(entityManagerFactory)
    .queryProvider(queryProvider)
    .saveState(false)
    .build()