💡 순수 JDBC

어마 무시하게 복잡 하므로 그냥 이런게 있구나 하고 넘어가도록 하자..

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💡 Jdbc Template

스프링 JdbcTemplate과 MyBatis 같은 라이브러리는 순수 JDBC의 반복 코드를 대부분 제거해준다.
하지만 SQL은 직접 작성해야 한다.

• JdbcTemplateMemberRepository

public class JdbcTemplateMemberRepository implements MemberRepository {
    private final JdbcTemplate jdbcTemplate;
    public JdbcTemplateMemberRepository(DataSource dataSource) {
        jdbcTemplate = new JdbcTemplate(dataSource);
    }

    @Override
    public Member save(Member member) {
        SimpleJdbcInsert jdbcInsert = new SimpleJdbcInsert(jdbcTemplate);
        jdbcInsert.withTableName("member").usingGeneratedKeyColumns("id");

        Map<String, Object> parameters = new HashMap<>();
        parameters.put("name", member.getName());

        Number key = jdbcInsert.executeAndReturnKey(new MapSqlParameterSource(parameters));

        member.setId(key.longValue());
        return member;
    }
    
    @Override
    public Optional<Member> findById(Long id) {
        List<Member> result = jdbcTemplate.query("select * from member where id = ?", memberRowMapper(), id);
        return result.stream().findAny();
    }
    
    @Override
    public List<Member> findAll() {
        return jdbcTemplate.query("select * from member", memberRowMapper());
    }
    
    @Override
    public Optional<Member> findByName(String name) {
        List<Member> result = jdbcTemplate.query("select * from member where name = ?", memberRowMapper(), name);
        return result.stream().findAny();
    }
    
    private RowMapper<Member> memberRowMapper() {
        return (rs, rowNum) -> {
            Member member = new Member();
            member.setId(rs.getLong("id"));
            member.setName(rs.getString("name"));

            return member;
        };
    }
}

• SpringConfig

@Configuration
public class SpringConfig {
    private final DataSource dataSource;
    private final EntityManager em;

    public SpringConfig(DataSource dataSource, EntityManager em) {
        this.dataSource = dataSource;
        this.em = em;
    }

    @Bean
    public MemberService memberService() {
        return new MemberService(memberRepository());
    }

    @Bean
    public MemberRepository memberRepository() {
//        return new MemoryMemberRepository();
//        return new JdbcMemberRepository(dataSource);
  	      return new JdbcTemplateMemberRepository(dataSource);
//        return new JpaMemberRepository(em);
    }
}

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💡 JPA

기존의 반복 코드는 물론이고, 기본적인 SQL도 JPA가 직접 만들어서 실행한다.
SQL과 데이터 중심의 설계에서 객체 중심의 설계로 패러다임을 전환

개발 생산성을 크게 높일 수 있다.

• JpaMemberRepository

public class JpaMemberRepository implements MemberRepository {

    private final EntityManager em;
    public JpaMemberRepository(EntityManager em) {
        this.em = em;
    }
    public Member save(Member member) {
        em.persist(member);
        return 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 Optional<Member> findByName(String name) {
        List<Member> result = em.createQuery("select m from Member m where m.name = :name", Member.class)
                .setParameter("name", name)
                .getResultList();
        return result.stream().findAny();
    }

}

• SpringConfig

@Configuration
public class SpringConfig {
    private final DataSource dataSource;
    private final EntityManager em;

    public SpringConfig(DataSource dataSource, EntityManager em) {
        this.dataSource = dataSource;
        this.em = em;
    }

    @Bean
    public MemberService memberService() {
        return new MemberService(memberRepository());
    }

    @Bean
    public MemberRepository memberRepository() {
//        return new MemoryMemberRepository();
//        return new JdbcMemberRepository(dataSource);
//        return new JdbcTemplateMemberRepository(dataSource);
        return new JpaMemberRepository(em);
    }
}

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💡 스프링 데이터 JPA

👉 스프링 데이터 JPA가 SpringDataJpaMemberRepository 를 스프링 빈으로 자동 등록해준다.

• SpringDataJpaMemberRepository

public interface SpringDataJpaMemberRepository extends JpaRepository<Member, Long>, MemberRepository{

    @Override
    Optional<Member> findByName(String name);
}

• SpringConfig

@Configuration
public class SpringConfig {

    private final MemberRepository memberRepository;

    @Autowired
    public SpringConfig(MemberRepository memberRepository) {
        this.memberRepository = memberRepository;
    }

    @Bean
    public MemberService memberService() {
        return new MemberService(memberRepository);
    }
}

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강의 출처

[인프런 - 김영한] 스프링 입문 - 코드로 배우는 스프링 부트, 웹 MVC, DB 접근 기술