스프링MVC 입문19

순수 JDBC

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환경 설정(build.gradle)

implementation 'org.springframework.boot:spring-boot-starter-jdbc'
runtimeOnly 'com.h2database:h2'

• 스프링부트 2.4부터는 "spring.datasource.username=sa"를 꼭 추가해주어야 함

 

Jdbc 리포지토리 구현

JDBC API로 직접 코딩하는 것은 20년 전 이야기이다.

따라서 고대 개발자들이 이렇게 고생하고 살았구나 생각하고

정신건강을 위해 참고만 하고 넘어가자

 

Jdbc 회원 리포지토리

package com.danny.learningspring.repository;

import com.danny.learningspring.domain.Member;
import org.springframework.jdbc.datasource.DataSourceUtils;
import javax.sql.DataSource;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Optional;
public class JdbcMemberRepository implements MemberRepository {
    private final DataSource dataSource;
    public JdbcMemberRepository(DataSource dataSource) {
        this.dataSource = dataSource;
    }
    @Override
    public Member 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 new SQLException("id 조회 실패");
            }
            return member;
        } catch (Exception e) {
            throw new IllegalStateException(e);
        } finally {
            close(conn, pstmt, rs);
        }
    }
    @Override
    public Optional<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 = new Member();
                member.setId(rs.getLong("id"));
                member.setName(rs.getString("name"));
                return Optional.of(member);
            } else {
                return Optional.empty();
            }
        } catch (Exception e) {
            throw new IllegalStateException(e);
        } finally {
            close(conn, pstmt, rs);
        }
    }
    @Override
    public List<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 = new ArrayList<>();
            while(rs.next()) {
                Member member = new Member();
                member.setId(rs.getLong("id"));
                member.setName(rs.getString("name"));
                members.add(member);
            }
            return members;
        } catch (Exception e) {
            throw new IllegalStateException(e);
        } finally {
            close(conn, pstmt, rs);
        }
    }
    @Override
    public Optional<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 = new Member();
                member.setId(rs.getLong("id"));
                member.setName(rs.getString("name"));
                return Optional.of(member);
            }
            return Optional.empty();
        } catch (Exception e) {
            throw new IllegalStateException(e);
        } finally {
            close(conn, pstmt, rs);
        }
    }
    private Connection getConnection() {
        return DataSourceUtils.getConnection(dataSource);
    }
    private void close(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 void close(Connection conn) throws SQLException {
        DataSourceUtils.releaseConnection(conn, dataSource);
    }
}

• private final DataSource dataSource; -- DB에 붙일 때 필요
• String sql = "insert into member(name) values(?)"; -- 쿼리문
• Connection conn = null; -- 커넥터
• pstmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
  
  • DB상에 AUTO_INCREMENT로 인해 자동으로 생성되어진 key(=id)를 가져오는 쿼리
• pstmt.executeUpdate(); -- 쿼리문이 들어가는 시점
• rs = pstmt.getGeneratedKeys(); -- id값을 반환 받음
• member.setId(rs.getLong(1)); -- return된 result에서 id값을 꺼냄
• close(conn, pstmt, rs); -- 사용한 자원들 Release

 

SpringConfig

package com.danny.learningspring;

import com.danny.learningspring.repository.JdbcMemberRepository;
import com.danny.learningspring.repository.MemberRepository;
import com.danny.learningspring.repository.MemoryMemberRepository;
import com.danny.learningspring.service.MemberService;
import lombok.RequiredArgsConstructor;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;

@Configuration
@RequiredArgsConstructor
public class SpringConfig {


    private final DataSource dataSource;

//    @Autowired
//    public SpringConfig(DataSource dataSource) {
//        this.dataSource = dataSource;
//    }

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

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

• DataSource -- 데이터베이스 커넥션을 획득할 때 사용하는 객체
• 스프링 부트는 데이터베이스 커넥션 정보를 바탕으로 DataSource를 생성하고 스프링 빈으로 만들어둔다. 그래서 DI를 받을 수 있음
• 스프링의 DI (Dependencies Injection)을 사용하면 기존 코드를 전혀 손대지 않고, 설정만으로 구현 클래스를 변경할 수 있음
• 개방-폐쇄 원칙(OCP, Open-Closed Principle)
  • 확장에는 열려있고, 수정, 변경에는 닫혀있다.