[Data JPA] 기본적인 사용법과 Dto 조회하기, 파라미터 바인딩

사용법

실습용 Member Entity

// Member Entity
package study.demo.Entity;

import jakarta.persistence.*;
import lombok.*;

@Entity
@Setter @Getter
@NoArgsConstructor(access = AccessLevel.PROTECTED)
@ToString(of = {"id","username","age"})
public class Member {

    @Id @GeneratedValue
    @Column(name = "member_id")
    private Long id;
    private String username;
    private int age;

    @ManyToOne
    @JoinColumn(name = "team_id")
    private Team team;

    public Member(String username){
        this.username = username;
    }
    public void changeTeam(Team team){
        this.team = team;
        team.getMembers().add(this);
    }

}

Member Repository

• interface를 만들어준 뒤 JpaRepository를 extends 해준다. 
• 제네릭엔 클래스와 Entity의 Id 타입을 넣어주면 됨. 
• 메서드 이름으로 쿼리 생성

// Repository
package study.demo.repository;

import org.springframework.data.jpa.repository.JpaRepository;
import study.demo.Entity.Member;

import java.util.List;

public interface MemberRepository extends JpaRepository<Member,Long> {
    List<Member> findAll();
}

 

• 쿼리를 이용할 수도 있음.
• @Param("age") => 파라미터 바인딩
  • :age 에 값을 넣어주는 작업임. 

@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);

// List를 파라미터 값으로 넣을 수도 있다.
@Query("select m from Member m where m.username in :names)
List<Member> findByNames(@Param("names") List<String> names);

---

// 기존 방식
@Repository
public class MemberJpaRepository {
    @PersistenceContext
    private EntityManager em;
    

    public Member find(Long id){
        return em.find(Member.class,id);
    }
}

 

---

@Query 값, DTO 조회하기 

MemberDto

package study.demo.dto;

public class MemberDto {
    private Long id;
    private String username;
    private String teamname;
}

Member Repository

• Jpa에서 쓰던 방식과 거의 비슷하다.

@Query("select new study.demo.dto.MemberDto(m.id, m.username, t.name) from Member m join m.team t")
List<MemberDto> findMemberDto();