Specifications(명세)

• Specifications
• Query By Example
• Projections
• 네이티브 쿼리

Specifications을 지원하는데 JPA Criteria를 활용해서 개념을 사용할 수 있도록 지원해준다.

=> 실무에서 잘 사용하지 않는다.

 

술어(predicate)

• 참 또는 거짓으로 평가
• AND OR 같은 연산자로 조합해서 다양한 검색조건을 쉽게 생성(디자인 패턴을 컴포지트 패턴으로 생성)
• 예) 검색 조건 하나하나
• 스프링 데이터 JPA는 `org.springframework.data.jap.domain.Specification` 클래스로 정의

 

사용방법을 보고 간단하게 넘어가자.

// MemberRepository Interface

public interface MemberRepository extends JpaRepository<Member, Long>, MemberRepositoryCustom, JpaSpecificationExecutor<Member> {

    List<Member> findByUsernameAndAgeGreaterThan(String username, int age);

 

아래와 같이 테스트 케이스를 작성해주고

@Test
public void specBasic() {
    // given
    Team teamA = new Team("teamA");
    em.persist(teamA);

    Member m1 = new Member("m1", 0, teamA);
    Member m2 = new Member("m2", 0, teamA);
    em.persist(m1);
    em.persist(m2);

    em.flush();
    em.clear();

    // when
    memberRepository.findAll();
}

 

MemberSpec을 만든 후에

아래와 같이 코드 작성

// MemberSpec

package study.datajpa.repository;

import org.springframework.data.jpa.domain.Specification;
import org.springframework.util.StringUtils;
import study.datajpa.entity.Member;
import study.datajpa.entity.Team;

import javax.persistence.criteria.*;

public class MemberSpec {


    // teamName 검색조건으로 넣을 것이다.
    public static Specification<Member> teamName(final String teamName) {
        return (root, query, builder) -> {

            if (StringUtils.isEmpty(teamName)) {
                return null;
            }

            // JPA Criteria 문법 => JPQL 만듬
            Join<Member, Team> t = root.join("team", JoinType.INNER);// 회원과 조인
            return builder.equal(t.get("name"), teamName);
        };
    }

    public static Specification<Member> username(final String username) {
        return (Specification<Member>) (root, query, builder) ->
                builder.equal(root.get("username"), username);
    }
}

 

테스트 코드에 when절을 작성후에 실행시키면

@Test
public void specBasic() {
    // given
    Team teamA = new Team("teamA");
    em.persist(teamA);

    Member m1 = new Member("m1", 0, teamA);
    Member m2 = new Member("m2", 0, teamA);
    em.persist(m1);
    em.persist(m2);

    em.flush();
    em.clear();

    // when

    Specification<Member> spec = MemberSpec.username("m1").and(MemberSpec.teamName("teamA"));
    List<Member> result = memberRepository.findAll(spec);

    Assertions.assertThat(result.size()).isEqualTo(1);
}

 

쿼리 나가는 걸 보면 아래와 같다.

select
        member0_.member_id as member_i1_1_,
        member0_.age as age2_1_,
        member0_.created_date as created_3_1_,
        member0_.tema_id as tema_id5_1_,
        member0_.username as username4_1_ 
    from
        member member0_ 
    inner join
        team team1_ 
            on member0_.tema_id=team1_.team_id 
    where
        member0_.username=? 
        and team1_.name=?
2022-04-19 15:50:34.661  INFO 71773 --- [           main] p6spy                                    : #1650351034661 | took 0ms | statement | connection 3| url jdbc:h2:tcp://localhost/~/datajpa
select member0_.member_id as member_i1_1_, member0_.age as age2_1_, member0_.created_date as created_3_1_, member0_.tema_id as tema_id5_1_, member0_.username as username4_1_ from member member0_ inner join team team1_ on member0_.tema_id=team1_.team_id where member0_.username=? and team1_.name=?
select member0_.member_id as member_i1_1_, member0_.age as age2_1_, member0_.created_date as created_3_1_, member0_.tema_id as tema_id5_1_, member0_.username as username4_1_ from member member0_ inner join team team1_ on member0_.tema_id=team1_.team_id where member0_.username='m1' and team1_.name='teamA';

 

• 실무에서는 JPA Criteria를 거의 안쓴다! QueryDSL을 사용하자.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

<출처 김영한: 실전! 스프링 데이터 JPA >

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