MemberJpaRepository

package study.querydsl.repository;

import com.querydsl.jpa.impl.JPAQueryFactory;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Repository;
import study.querydsl.entity.Member;

import javax.persistence.EntityManager;
import java.util.List;
import java.util.Optional;

import static study.querydsl.entity.QMember.member;

@Repository
@RequiredArgsConstructor
public class MemberJpaRepository {

    public final EntityManager em;
    private final JPAQueryFactory queryFactory;

    public void save(Member member) {
        em.persist(member);
    }

    public Optional<Member> findById(Long id) {
        Member member = em.find(Member.class, id);
        return Optional.ofNullable(member);
    }

    public List<Member> findAll() {
        return em.createQuery("select m from Member m", Member.class)
                .getResultList();
    }

    public List<Member> findAll_Querydsl() {
        return queryFactory
                .selectFrom(member)
                .fetch();
    }

    public List<Member> findByUsername(String username) {
        return em.createQuery("select m from Member m where m.username = :username", Member.class)
                .setParameter("username", username)
                .getResultList();
    }

    public List<Member> findByUsername_Querydsl(String username) {
        return queryFactory
                .selectFrom(member)
                .where(member.username.eq(username))
                .fetch();
    }


}

• JPQL과 Querydsl를 사용하여 2가지 버전으로 메소드를 구현하였다.

• JPQL은 파라미터를 바인딩할때 setParameter()를 사용해야하지만
  Querydsl은 where() 조건안에서 eq()와 함께 사용해줘서 더욱 편리하다.

MemberJpaRepositoryTest

package study.querydsl.repository;

import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.transaction.annotation.Transactional;
import study.querydsl.entity.Member;

import javax.persistence.EntityManager;

import java.util.List;

import static org.assertj.core.api.Assertions.*;

@SpringBootTest
@Transactional
class MemberJpaRepositoryTest {

    @Autowired EntityManager em;

    @Autowired MemberJpaRepository memberJpaRepository;

    @Test
    public void basicTest() {
        Member member = new Member("member1", 10);
        memberJpaRepository.save(member);

        Member findMember = memberJpaRepository.findById(member.getId()).get();
        assertThat(member).isEqualTo(findMember);

        List<Member> all = memberJpaRepository.findAll();
        assertThat(all).containsExactly(findMember);

        List<Member> byUsername = memberJpaRepository.findByUsername(member.getUsername());
        assertThat(byUsername).containsExactly(member);
    }

    @Test
    public void basicTest_Querydsl() {
        Member member = new Member("member1", 10);
        memberJpaRepository.save(member);

        List<Member> findMember = memberJpaRepository.findAll_Querydsl();
        assertThat(findMember).containsExactly(member);

        List<Member> byUsernameQuerydsl = memberJpaRepository.findByUsername_Querydsl(member.getUsername());
        assertThat(byUsernameQuerydsl).containsExactly(member);
    }
}

• JPQL과 Querydsl로 test코드를 짠 결과 값은 동일했다.

Spring bean 주입

QueryFactory와 EntityManager를 사용하려면 아래와 같이 생성자를 주입해줘야 한다.

@Repository
public class MemberJpaRepository {

    public final EntityManager em;
    private final JPAQueryFactory queryFactory;

    public MemberJpaRepository(EntityManager em) {
        this.em = em;
        this.queryFactory = new JPAQueryFactory(em);
    }
}

하지만 이런식으로 하기보다는 편리하게 하는 방법이 있다.

package study.querydsl;

import com.querydsl.jpa.impl.JPAQueryFactory;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

import javax.persistence.EntityManager;

@SpringBootApplication
public class QuerydslApplication {

	public static void main(String[] args) {
		SpringApplication.run(QuerydslApplication.class, args);
	}

	@Bean
	JPAQueryFactory jpaQueryFactory(EntityManager em) {
		return new JPAQueryFactory(em);
	}
}

SpringBootApplication에서 @Bean으로 주입하면 편리하다.

@Repository
@RequiredArgsConstructor
public class MemberJpaRepository {

    public final EntityManager em;
    private final JPAQueryFactory queryFactory;
}

@RequiredArgsConstructor를 사용하여 생성자를 생성할 수 있다.