SpringSpring Data JPA

Spring Data JPA - 반환 타입

목차

반환 타입

List<Member> findListByUsername(String username); // 반환 타입 : 컬랙션
Member findMemberByUsername(String username); // 반환 타입 : 단건
Optional<Member> findOptionalByUsername(String useranme); // 반환 티입 : 단건 Optional
public interface MemberRepository extends JpaRepository<Member, Long> {
    List<Member> findByUsernameAndAgeGreaterThan(String username, int age);

    @Query("select m from Member m where m.username = :username and m.age = :age")
    List<Member> findUser(@Param("username") String username, @Param("age") int age);

    // 값으로 조회하기
    @Query("select m.username from Member m")
    List<String> findUsernameList();

    // DTO로 조회하기
    @Query("select new com.example.datajpa.dto.MemberDto( m.id, m.username, t.name)from Member m join m.team t")
    List<MemberDto> findMemberByDto();

    @Query("select m from Member m where m.username in :names")
    List<Member> findByNames(@Param("names") Collection<String> names);

    List<Member> findListByUsername(String username); // 반환 타입 : 컬랙션
    Member findMemberByUsername(String username); // 반환 타입 : 단건
    Optional<Member> findOptionalByUsername(String useranme); // 반환 티입 : 단건 Optional
}
@Test
public void returnType(){
    Member member1 = new Member("AAA", 10);
    Member member2 = new Member("BBB", 20);
    memberRepository.save(member1);
    memberRepository.save(member2);

    List<Member> members = memberRepository.findListByUsername("AAA");
    Member member = memberRepository.findMemberByUsername("AAA");
    Optional<Member> optional = memberRepository.findOptionalByUsername("AAA");

    assertThat(members).isInstanceOf(List.class);
    assertThat(member).isInstanceOf(Member.class);
    assertThat(optional).isInstanceOf(Optional.class);
}
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