인프런 커뮤니티 질문&답변

학습하는 분들께 도움이 되고, 더 좋은 답변을 드릴 수 있도록 질문전에 다음을 꼭 확인해주세요.

1. 강의 내용과 관련된 질문을 남겨주세요.
2. 인프런의 질문 게시판과 자주 하는 질문(링크)을 먼저 확인해주세요.
(자주 하는 질문 링크: https://bit.ly/3fX6ygx)
3. 질문 잘하기 메뉴얼(링크)을 먼저 읽어주세요.
(질문 잘하기 메뉴얼 링크: https://bit.ly/2UfeqCG)

질문 시에는 위 내용은 삭제하고 다음 내용을 남겨주세요.
=========================================
[질문 템플릿]
1. 강의 내용과 관련된 질문인가요? (예/아니오)
2. 인프런의 질문 게시판과 자주 하는 질문에 없는 내용인가요? (예/아니오)
3. 질문 잘하기 메뉴얼을 읽어보셨나요? (예/아니오)

[질문 내용]
여기에 질문 내용을 남겨주세요.

java.lang.NullPointerException: Cannot invoke "hello.jdbc.repository.MemberRepositoryV1.save(hello.jdbc.domain.Member)" because "this.memberRepository" is null

memberRepositoryV1.save 하는 과정에서 널포인터익셉션이 났습니다.

package hello.jdbc.repository;

import hello.jdbc.connection.DBConnectionUtil;
import hello.jdbc.domain.Member;
import lombok.AllArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.jdbc.support.JdbcUtils;

import javax.sql.DataSource;
import java.sql.*;
import java.util.NoSuchElementException;

/**
 * JDBA - DataSource 사용, JdbcUtils 사용
 */
@Slf4j
public class MemberRepositoryV1 {

    private final DataSource dataSource;

    public MemberRepositoryV1(DataSource dataSource) {
       this.dataSource = dataSource;
    }

    public Member save(Member member) throws SQLException {

        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) {
            log.info("db error", e);
            throw e;
        }finally {
            close(con, pstmt, null);
        }
    }

    public Member findById(String memberId) throws SQLException {
        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) {
            log.info("db error", e);
            throw e;
        }finally {
            close(con, pstmt, rs);
        }


    }


    public void update(String memberId, int money) throws SQLException {
        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) {
            log.info("db error", e);
            throw e;
        }finally {
            close(con, pstmt, null);

        }

    }


    public void delete(String memberId) throws SQLException {
        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) {
            log.info("db error", e);
            throw e;
        }finally {
            close(con, pstmt, null);

        }

    }


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

        JdbcUtils.closeResultSet(rs);
        JdbcUtils.closeStatement(stmt);
        JdbcUtils.closeConnection(con);
    }
    private Connection getConnection() throws SQLException {
        Connection con = dataSource.getConnection();
        log.info("get connection={}, class={}", con, con.getClass());
        return con;
    }

}

package hello.jdbc.repository;

import com.zaxxer.hikari.HikariDataSource;
import hello.jdbc.connection.ConnectionConst;
import hello.jdbc.domain.Member;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import org.springframework.jdbc.datasource.DriverManagerDataSource;

import java.net.URL;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.NoSuchElementException;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatThrownBy;

@Slf4j
class MemberRepositoryV1Test {

    MemberRepositoryV1 repository;

    @BeforeEach
    void beforeEach() {
        //기본 driverManager - 항상 새로운 커넥션을 획득
        //  DriverManagerDataSource dataSource = new DriverManagerDataSource(ConnectionConst.URL, ConnectionConst.USERNAME, ConnectionConst.PASSWORD);

        //커넥션 풀링
        HikariDataSource dataSource = new HikariDataSource();
        dataSource.setJdbcUrl(ConnectionConst.URL);
        dataSource.setUsername(ConnectionConst.USERNAME);
        dataSource.setPassword(ConnectionConst.PASSWORD);


        repository = new MemberRepositoryV1(dataSource);
    }

    @Test
    void crud() throws SQLException {
        //save
        Member member = new Member("memberV2", 10000);
        repository.save(member);

        //findById
        Member findMember = repository.findById(member.getMemberId());
        log.info("findMember={}", findMember);
        log.info("member != findMember {}", member == findMember);
        assertThat(findMember).isEqualTo(member);

        //update
        repository.update(member.getMemberId(), 20000);
        Member updateMember = repository.findById(member.getMemberId());
        assertThat(updateMember.getMoney()).isEqualTo(20000);

        //delete
        repository.delete(member.getMemberId());
        assertThatThrownBy(() -> repository.findById(member.getMemberId()))
              .isInstanceOf(NoSuchElementException.class);
    }

}