Srping DB접근 기술(JDBC, JPA)

스프링 DB 접근 기술 종류

• JDBC
• JDBCTemplate
• JPA
• Spring Data JPA

 

JDBC(Java Database Connectivity)

JDBC는 자바에서 데이터베이스를 접속할 수 잇도록 하는 자바 API이다. JDBC는 데이터 베이스에서 접근을 제공한다.

DataSource는 데이터베이스 커넥션을 획득할 때 사용하는 객체다.

기본적인 조회

@Override
publicMember save(Member member) {
    String sql = "insert into member(name) values(?)";

    Connection conn =null;
    PreparedStatement pstmt =null;
    ResultSet rs =null;
try{
        conn = getConnection();
        pstmt = conn.prepareStatement(sql,
                Statement.RETURN_GENERATED_KEYS);
        pstmt.setString(1, member.getName());
        pstmt.executeUpdate();
        rs = pstmt.getGeneratedKeys();
if(rs.next()) {
            member.setId(rs.getLong(1));
        }else{
throw newSQLException("id 조회 실패");
        }
returnmember;
    }catch(Exception e) {
throw newIllegalStateException(e);
    }finally{
        close(conn, pstmt, rs);
    }
}

@Override
publicOptional<Member> findById(Long id) {
    String sql = "select * from member where id = ?";
    Connection conn =null;
    PreparedStatement pstmt =null;

    ResultSet rs =null;
try{
        conn = getConnection();
        pstmt = conn.prepareStatement(sql);
        pstmt.setLong(1, id);
        rs = pstmt.executeQuery();
if(rs.next()) {
            Member member =newMember();
            member.setId(rs.getLong("id"));
            member.setName(rs.getString("name"));
returnOptional.of(member);
        }else{
returnOptional.empty();
        }
    }catch(Exception e) {
throw newIllegalStateException(e);
    }finally{
        close(conn, pstmt, rs);
    }
}

@Override
publicList<Member> findAll() {
    String sql = "select * from member";
    Connection conn =null;
    PreparedStatement pstmt =null;
    ResultSet rs =null;
try{
        conn = getConnection();
        pstmt = conn.prepareStatement(sql);
        rs = pstmt.executeQuery();

        List<Member> members =newArrayList<>();
while(rs.next()) {
            Member member =newMember();
            member.setId(rs.getLong("id"));
            member.setName(rs.getString("name"));
            members.add(member);
        }
returnmembers;
    }catch(Exception e) {
throw newIllegalStateException(e);
    }finally{
        close(conn, pstmt, rs);
    }
}

@Override
publicOptional<Member> findByName(String name) {
    String sql = "select * from member where name = ?";
    Connection conn =null;
    PreparedStatement pstmt =null;
    ResultSet rs =null;
try{
        conn = getConnection();
        pstmt = conn.prepareStatement(sql);
        pstmt.setString(1, name);
        rs = pstmt.executeQuery();
if(rs.next()) {
            Member member =newMember();
            member.setId(rs.getLong("id"));
            member.setName(rs.getString("name"));
returnOptional.of(member);
        }

returnOptional.empty();
    }catch(Exception e) {
throw newIllegalStateException(e);
    }finally{
        close(conn, pstmt, rs);
    }
}

privateConnection getConnection() {
returnDataSourceUtils.getConnection(dataSource);
}

private voidclose(Connection conn, PreparedStatement pstmt, ResultSet rs) {
try{
if(rs !=null) {
            rs.close();
        }
    }catch(SQLException e) {
        e.printStackTrace();
    }
try{
if(pstmt !=null) {
            pstmt.close();
        }
    }catch(SQLException e) {
        e.printStackTrace();
    }
try{
if(conn !=null) {
            close(conn);
        }
    }catch(SQLException e) {
        e.printStackTrace();
    }
}

private voidclose(Connection conn)throwsSQLException {
    DataSourceUtils.releaseConnection(conn, dataSource);

}

---

JDBC Template

스프링 JdbcTemplate과 MyBatis 같은 라이브러리는 JDBC API에서 본 반복 코드를 대부분 제거해준다. 하지만 SQL은 직접 작성해야 한다.

JDBC Template 구현방식

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

    Map<String, Object> parameters =newHashMap<>();
    parameters.put("name", member.getName());
    Number key = jdbcInsert.executeAndReturnKey(newMapSqlParameterSource(parameters));
    member.setId(key.longValue());
returnmember;
}

@Override
publicOptional<Member> findById(Long id) {
    List<Member> result = jdbcTemplate.query("select * from member where id = ? ", memberRowMapper(), id);
returnresult.stream().findAny();
}

@Override
publicList<Member> findAll() {
returnjdbcTemplate.query("select * from member", memberRowMapper());
}

@Override
publicOptional<Member> findByName(String name) {
    List<Member> result = jdbcTemplate.query("select * from member where name = ? ", memberRowMapper(), name);
returnresult.stream().findAny();
}

privateRowMapper<Member> memberRowMapper() {
return(rs, rowNum) -> {
        Member member =newMember();
        member.setId(rs.getLong("id"));
        member.setName(rs.getString("name"));
returnmember;
    };
}

---

JPA

JPA(Java Persistence API)는 자바 진영의 ORM 기술 표준

ORM → Object-relational mapping

객체는 객체대로 설계를 진행하고 관계형 DB는 독립적으로 설계한다.

ORM은 중간에서 매핑시켜준다.

private finalEntityManager em;

publicJpaMemberRepository(EntityManager em) {
this.em = em;
}

@Override
publicMember save(Member member) {
    em.persist(member);
returnmember;
}

@Override
publicOptional<Member> findById(Long id) {
    Member member = em.find(Member.class, id);
returnOptional.ofNullable(member);
}

@Override
publicOptional<Member> findByName(String name) {
    List<Member> result = em.createQuery("select m from Member m where m.name = :name", Member.class)
            .setParameter("name", name)
            .getResultList();

returnresult.stream().findAny();
}

@Override
publicList<Member> findAll() {
returnem.createQuery("Select m from Member m", Member.class).getResultList();
}

---

Spring Data JPA

JPA기반 데이터 액세스 계층에 대한 향상된 지원을 해준다. 데이터 액세스 기술을 사용하는 spring 기반 애플리케이션을 나은 방향으로 구축 할 수 있다.

Spring Data JPA

Spring Data JPA

public interfaceSpringDataJpaMemberRepositoryextendsJpaRepository<Member,Long>, MemberRepository {

//select m from Member m where m.name = ?
@Override
Optional<Member> findByName(String name);

}

---

마무리

JPA를 공부하기로 마음을 먹어서 JPA를 공부하고 Spring Data JPA를 더 깊이 있게 다루기로 하였다.

 

 

출처 : Inflearn - 김영한 강사님 스프링 입문 - 코드로 배우는 스프링 부트, 웹 MVC, DB 접근 기술