["slug" being an entity attribute]
Spring Data offers an existsBy query method, which we can define in the PostRepository, as follows:
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@Repository
public interface PostRepository
extends JpaRepository<Post, Long> {
boolean existsBySlug(String slug);
}
[another] option to emulate existence is using a CASE WHEN EXISTS native SQL query:
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@Repository
public interface PostRepository
extends JpaRepository<Post, Long> {
@Query(value = """
SELECT
CASE WHEN EXISTS (
SELECT 1
FROM post
WHERE slug = :slug
)
THEN 'true'
ELSE 'false'
END
""",
nativeQuery = true
)
boolean existsBySlugWithCase(@Param("slug") String slug);
}
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M. Nowostawski, M. Purvis, and S. Cranefield. Engineering Self-Organising Systems, volume 3464 of Lecture Notes in Computer Science, page 100-122. Springer, (2004)
C. Simmermacher, D. Deng, and S. Cranefield. Industrial Conference on Data Mining, volume 4065 of Lecture Notes in Computer Science, page 444-458. Springer, (2006)
T. Raimbault, D. Genest, and S. Loiseau. Proceedings of the 13th International Conference on Conceptual Structures (ICCS 2005), volume 3596 of Lecture Notes in Computer Science, page 353-366. Springer, (2005)