Spring Data JPA huondoa boilerplate ya kuandika DAO classes. Unatangaza repository interface; wakati wa kuanza Spring huzalisha proxy implementation inayoungwa mkono na JPA/Hibernate. Huandiki kamwe entityManager.persist(...) kwa CRUD ya kimsingi.
{
Long id;
String email;
active;
}
<User, Long> {
Optional<User> ;
List<User> ;
}
Derived queries husomeka vizuri kwa vigezo rahisi lakini hulipuka kwa urefu kadri masharti yanavyoongezeka. Hilo linapotokea, shuka hadi @Query ya wazi:
@Query("SELECT u FROM User u WHERE u.email = :email") // JPQL, not SQL
Optional<User> lookup(@Param("email") String email);
// Native SQL when you need DB-specific features:
@Query(value = "SELECT * FROM users WHERE active = true", nativeQuery = true)
List<User> findActiveNative();
Page<User> findByActiveTrue(Pageable pageable); // pass PageRequest.of(0, 20)
Wahoji huchunguza kama unaelewa kile kinachozalishwa nyuma ya interface. Ishara imara: kujua derived-query keywords, kuchagua @Query wakati method names zinapokuwa ngumu, kutumia Pageable badala ya kupakia tables nzima, na kuwa na ufahamu kuwa lazy associations zinaweza kuchochea tatizo la N+1 — mada ambayo mara nyingi watasukuma hadi swali linalofuata.
Maktaba ya maswali ya mahojiano ya IT yenye majibu ya kina — kutoka Junior hadi Senior.
Changia