[Spring] 스프링 DB 1편 06

김영한님의 스프링 DB 1편 을 공부하여 정리한 글입니다.

런타임 예외 적용

Interface

public interface MemberRepository {
    Member save(Member member);
    Member findById(String memberId);
    void update(String memberId, int money);
    void delete(String memberId);
}

Exception

public class MyDbException extends RuntimeException {
    public MyDbException() {
    }

    public MyDbException(String message) {
        super(message);
    }

    public MyDbException(String message, Throwable cause) {
        super(message, cause);
    }

    public MyDbException(Throwable cause) {
        super(cause);
    }
}

Repositoty

@Slf4j
public class MemberRepositoryV4_1 implements MemberRepository {

    private final DataSource dataSource;

    public MemberRepositoryV4_1(DataSource dataSource) {
        this.dataSource = dataSource;
    }

    @Override
    public Member save(Member member) {
        String sql = "insert into member(member_id, money) values(?,?)";

        Connection con = null;
        PreparedStatement pstmt = null;

        try {
            con = getConnection();
            pstmt = con.prepareStatement(sql);
            pstmt.setString(1, member.getMemberId());
            pstmt.setInt(2, member.getMoney());
            pstmt.executeUpdate();
            return member;
        } catch (SQLException e) {
            throw new MyDbException(e);
        } finally {
            close(con, pstmt, null);
        }
    }

    @Override
    public Member findById(String memberId) {
        String sql = "select * from member where member_id = ?";

        Connection con = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;

        try {
            con = getConnection();
            pstmt = con.prepareStatement(sql);
            pstmt.setString(1, memberId);

            rs = pstmt.executeQuery();
            if (rs.next()) {
                Member member = new Member();
                member.setMemberId(rs.getString("member_id"));
                member.setMoney(rs.getInt("money"));
                return member;
            } else {
                throw new NoSuchElementException("member not found memberId=" + memberId);
            }
        } catch (SQLException e) {
            throw new MyDbException(e);
        } finally {
            close(con, pstmt, rs);
        }
    }

    @Override
    public void update(String memberId, int money) {
        String sql = "update member set money=? where member_id=?";

        Connection con = null;
        PreparedStatement pstmt = null;

        try {
            con = getConnection();
            pstmt = con.prepareStatement(sql);
            pstmt.setInt(1, money);
            pstmt.setString(2, memberId);
            int resultSize = pstmt.executeUpdate();
            log.info("resultSize={}", resultSize);
        } catch (SQLException e) {
            throw new MyDbException(e);
        } finally {
            close(con, pstmt, null);
        }
    }

    @Override
    public void delete(String memberId) {
        String sql = "delete from member where member_id=?";

        Connection con = null;
        PreparedStatement pstmt = null;

        try {
            con = getConnection();
            pstmt = con.prepareStatement(sql);
            pstmt.setString(1, memberId);
            pstmt.executeUpdate();
        } catch (SQLException e) {
            throw new MyDbException(e);
        } finally {
            close(con, pstmt, null);
        }
    }

    private void close(Connection con, Statement stmt, ResultSet rs) {

        JdbcUtils.closeResultSet(rs);
        JdbcUtils.closeStatement(stmt);
        //트랜젝션 동기화를 사용하려면 DataSourceUtils를 사용해야 한다.
        DataSourceUtils.releaseConnection(con, dataSource);
    }

    private Connection getConnection() throws SQLException {
        //트랜젝션 동기화를 사용하려면 DataSourceUtils를 사용해야 한다.
        Connection con = DataSourceUtils.getConnection(dataSource);
        log.info("get connection={}, class={}", con, con.getClass());
        return con;
    }
}

Service

@Slf4j
public class MemberServiceV4 {

    private final MemberRepository memberRepository;

    public MemberServiceV4(MemberRepository memberRepository) {
        this.memberRepository = memberRepository;
    }

    @Transactional
    public void accountTransfer(String fromId, String toId, int money) {
        //비즈니스 로직 수행
        bizLogic(fromId, toId, money);
    }

    private void bizLogic(String fromId, String toId, int money) {
        Member fromMember = memberRepository.findById(fromId);
        Member toMember = memberRepository.findById(toId);

        memberRepository.update(fromId, fromMember.getMoney() - money);
        validation(toMember);
        memberRepository.update(toId, toMember.getMoney() + money);
    }

    private void validation(Member toMember) {
        if (toMember.getMemberId().equals("ex")) {
            throw new IllegalStateException("이체중 예외 발생");
        }
    }
}

데이터 접근 예외 직접 만들기

데이터베이스 오류 코드

서비스 계층에서는 예외 복구를 위해 키 중복 오류를 확인할 수 있어야 한다.

MyDuplicateKeyException

public class MyDuplicateKeyException extends MyDbException {
    public MyDuplicateKeyException() {
    }

    public MyDuplicateKeyException(String message) {
        super(message);
    }

    public MyDuplicateKeyException(String message, Throwable cause) {
        super(message, cause);
    }

    public MyDuplicateKeyException(Throwable cause) {
        super(cause);
    }
}

Test

@Slf4j
public class ExTranslatorV1Test {

    Repository repository;
    Service service;

    @BeforeEach
    void init() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource(URL, USERNAME, PASSWORD);
        repository = new Repository(dataSource);
        service = new Service(repository);
    }

    @Test
    void duplicateKeySave() {
        service.create("myId");
        service.create("myId");
    }

    @Slf4j
    @RequiredArgsConstructor
    static class Service {
        private final Repository repository;

        public void create(String memberId) {
            try {
                repository.save(new Member(memberId, 0));
                log.info("saveId={}", memberId);
            } catch (MyDuplicateKeyException e) {
                log.info("키 중복,복구 시도");
                String retryId = generateNewId(memberId);
                log.info("retryId={}", retryId);
                repository.save(new Member(retryId, 0));
            } catch (MyDbException e) {
                log.info("데이터 접근 계층 예외", e);
                throw e;
            }


        }

        private String generateNewId(String memberId) {
            return memberId + new Random().nextInt(10000);
        }
    }

    @RequiredArgsConstructor
    static class Repository {
        private final DataSource dataSource;

        public Member save(Member member) {
            String sql = "insert into member(member_id,money) values(?,?)";
            Connection con = null;
            PreparedStatement pstmt = null;

            try {
                con = dataSource.getConnection();
                pstmt = con.prepareStatement(sql);
                pstmt.setString(1, member.getMemberId());
                pstmt.setInt(2, member.getMoney());
                pstmt.executeUpdate();
                return member;
            } catch (SQLException e) {
                //h2 db
                if (e.getErrorCode() == 23505) {
                    throw new MyDuplicateKeyException(e);
                }
                throw new MyDbException(e);
            } finally {
                JdbcUtils.closeStatement(pstmt);
                JdbcUtils.closeConnection(con);
            }
        }

    }
}

• Repository
  • e.getErrorCode() == 23505 : 오류 코드가 키 중복 오류( 23505 )인 경우
    MyDuplicateKeyException 을 새로 만들어서 서비스 계층에 던진다.
  • 나머지 경우 기존에 만들었던 MyDbException 을 던진다
• Service
  • 처음에 저장을 시도한다. 만약 리포지토리에서 MyDuplicateKeyException 예외가 올라오면 이 예외를 잡는다.
  • 예외를 잡아서 generateNewId(memberId) 로 새로운 ID 생성을 시도한다. 그리고 다시 저장한다.
  • 만약 복구할 수 없는 예외( MyDbException )면 로그만 남기고 다시 예외를 던진다.

스프링 예외 추상화 이해

스프링 데이터 접근 예외 계층

스프링이 제공하는 예외 변환기

스프링은 데이터베이스에서 발생하는 오류 코드를 스프링이 정의한 예외로 자동으로 변환해주는 변환기를 제공한다.

Test

@Slf4j
public class SpringExceptionTranslatorTest {

    DataSource dataSource;

    @BeforeEach
    void init(){
        dataSource = new DriverManagerDataSource(URL, USERNAME, PASSWORD);
    }

    @Test
    void sqlExceptionErrorCode(){
        String sql = "select bad grammer";

        try {
            Connection con = dataSource.getConnection();
            PreparedStatement stmt = con.prepareStatement(sql);
            stmt.executeQuery();
        } catch (SQLException e) {
            assertThat(e.getErrorCode()).isEqualTo(42122);
            int errorCode = e.getErrorCode();
            log.info("errorCode={}", errorCode);
            log.info("error", e);
        }
    }

    @Test
    void exceptionTranslator(){
        String sql = "select bad grammer";

        try {
            Connection con = dataSource.getConnection();
            PreparedStatement stmt = con.prepareStatement(sql);
            stmt.executeQuery();
        } catch (SQLException e){
            assertThat(e.getErrorCode()).isEqualTo(42122);
            SQLErrorCodeSQLExceptionTranslator exTranslator = new SQLErrorCodeSQLExceptionTranslator(dataSource);
            DataAccessException resultEx = exTranslator.translate("select", sql, e);
            log.info("resultEx",resultEx);
            assertThat(resultEx.getClass()).isEqualTo(BadSqlGrammarException.class);
        }
    }
}

• translate() 메서드의 첫번째 파라미터는 읽을 수 있는 설명이고,
  두번째는 실행한 sql, 마지막은 발생된 SQLException 을 전달하면 된다.
• 예제에서는 SQL 문법이 잘못되었으므로 BadSqlGrammarException 을 반환하는 것을 확인할 수 있다.

스프링이 어떻게 각각의 DB가 제공하는 SQL ErrorCode를 변환할 수 있는가?

sql-error-codes.xml

스프링 SQL 예외 변환기는 SQL ErrorCode를 이 파일에 대입해서
어떤 스프링 데이터 접근 예외로 전환 해야 할지 찾아낸다.

스프링 예외 추상화 적용

Repository

@Slf4j
public class MemberRepositoryV4_2 implements MemberRepository {

    private final DataSource dataSource;
    private final SQLExceptionTranslator exTranslator;

    public MemberRepositoryV4_2(DataSource dataSource) {
        this.dataSource = dataSource;
        this.exTranslator = new SQLErrorCodeSQLExceptionTranslator(dataSource);
    }

    @Override
    public Member save(Member member) {
        String sql = "insert into member(member_id, money) values(?,?)";

        Connection con = null;
        PreparedStatement pstmt = null;

        try {
            con = getConnection();
            pstmt = con.prepareStatement(sql);
            pstmt.setString(1, member.getMemberId());
            pstmt.setInt(2, member.getMoney());
            pstmt.executeUpdate();
            return member;
        } catch (SQLException e) {
            throw exTranslator.translate("save", sql, e);
        } finally {
            close(con, pstmt, null);
        }
    }

    @Override
    public Member findById(String memberId) {
        String sql = "select * from member where member_id = ?";

        Connection con = null;
        PreparedStatement pstmt = null;
        ResultSet rs = null;

        try {
            con = getConnection();
            pstmt = con.prepareStatement(sql);
            pstmt.setString(1, memberId);

            rs = pstmt.executeQuery();
            if (rs.next()) {
                Member member = new Member();
                member.setMemberId(rs.getString("member_id"));
                member.setMoney(rs.getInt("money"));
                return member;
            } else {
                throw new NoSuchElementException("member not found memberId=" + memberId);
            }
        } catch (SQLException e) {
            throw exTranslator.translate("findById", sql, e);
        } finally {
            close(con, pstmt, rs);
        }
    }

    @Override
    public void update(String memberId, int money) {
        String sql = "update member set money=? where member_id=?";

        Connection con = null;
        PreparedStatement pstmt = null;

        try {
            con = getConnection();
            pstmt = con.prepareStatement(sql);
            pstmt.setInt(1, money);
            pstmt.setString(2, memberId);
            int resultSize = pstmt.executeUpdate();
            log.info("resultSize={}", resultSize);
        } catch (SQLException e) {
            throw exTranslator.translate("update", sql, e);
        } finally {
            close(con, pstmt, null);
        }
    }

    @Override
    public void delete(String memberId) {
        String sql = "delete from member where member_id=?";

        Connection con = null;
        PreparedStatement pstmt = null;

        try {
            con = getConnection();
            pstmt = con.prepareStatement(sql);
            pstmt.setString(1, memberId);
            pstmt.executeUpdate();
        } catch (SQLException e) {
            throw exTranslator.translate("delete", sql, e);
        } finally {
            close(con, pstmt, null);
        }
    }

    private void close(Connection con, Statement stmt, ResultSet rs) {

        JdbcUtils.closeResultSet(rs);
        JdbcUtils.closeStatement(stmt);
        //트랜젝션 동기화를 사용하려면 DataSourceUtils를 사용해야 한다.
        DataSourceUtils.releaseConnection(con, dataSource);
    }

    private Connection getConnection() throws SQLException {
        //트랜젝션 동기화를 사용하려면 DataSourceUtils를 사용해야 한다.
        Connection con = DataSourceUtils.getConnection(dataSource);
        log.info("get connection={}, class={}", con, con.getClass());
        return con;
    }
}

• throw exTranslator.translate("save", sql, e)
  예외 변환기를 사용하여 예외를 던진다.

JDBC 반복 문제 해결 - JdbcTemplate

JDBC 반복 문제

• 커넥션 조회, 커넥션 동기화
• PreparedStatement 생성 및 파라미터 바인딩
• 쿼리 실행
• 결과 바인딩
• 예외 발생시 스프링 예외 변환기 실행
• 리소스 종료

스프링은 JDBC의 반복 문제를 해결하기 위해 JdbcTemplate 이라는 템플릿을 제공한다.

Repository

@Slf4j
public class MemberRepositoryV5 implements MemberRepository {

    private final JdbcTemplate template;

    public MemberRepositoryV5(DataSource dataSource) {
        this.template = new JdbcTemplate(dataSource);
    }

    @Override
    public Member save(Member member) {
        String sql = "insert into member(member_id, money) values(?,?)";
        template.update(sql, member.getMemberId(), member.getMoney());
        return member;
    }

    @Override
    public Member findById(String memberId) {
        String sql = "select * from member where member_id = ?";
        return template.queryForObject(sql, memberRowMapper(), memberId);
    }

    @Override
    public void update(String memberId, int money) {
        String sql = "update member set money=? where member_id=?";
        template.update(sql, money, memberId);
    }

    @Override
    public void delete(String memberId) {
        String sql = "delete from member where member_id=?";
        template.update(sql, memberId);
    }

    private RowMapper<Member> memberRowMapper() {
        return (rs, rowNum) -> {
            Member member = new Member();
            member.setMemberId(rs.getString("member_id"));
            member.setMoney(rs.getInt("money"));
            return member;
        };
    }
}

• JdbcTemplate은 트랜잭션을 위한 커넥션 동기화는 물론이고,
  예외 발생시 스프링 예외 변환기도 자동으로 실행해준다.