hello-spring\build.gradle

implementation 'org.springframework.boot:spring-boot-starter-jdbc'
runtimeOnly 'com.h2database:h2'
  • build.gradle 파일에 jdbc, h2 데이터베이스 관련 라이브러리 추가


hello-spring\src\main\resources\application.properties

spring.datasource.url=jdbc:h2:tcp://localhost/~/test
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.username=sa
  • 스프링 부트 데이터베이스 연결 설정 추가


※주의

  • 스프링 2.4부터는 spring.datasource.username=sa를 꼭 추가해야한다. 그렇지 않으면 Wrong user name or password오류가 발생한다. 참고로 마지막에 공백이 들어가면 같은 오류가 발생한다. 공백주의..


JDBC Repository 구현

  • 이렇게 JDBC API로 직접 코딩하는 것은 20여년 전 이야기이다. 그냥 고대 개발자들이 이렇게 고생하고 살았구나 생각하고, 정신건강을 위해 참고만 하고 넘어가자.


hello-spring\src\main\java\hello\hellospring\repository\JdbcMemberRepository.java

package hello.hellospring.repository;

import hello.hellospring.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); }
}


hello-spring\src\main\java\hello\hellospring\SpringConfig.java

package hello.hellospring;

import hello.hellospring.repository.JdbcMemberRepository;
import hello.hellospring.repository.MemberRepository;
import hello.hellospring.service.MemberService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

import javax.sql.DataSource;

@Configuration
public class SpringConfig {

    private DataSource dataSource;

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


    @Bean
    public MemberService memberService() {

        return new MemberService(memberRepository());
    }

    @Bean
    public MemberRepository memberRepository() {

        //return new MemoryMemberRepository();
        return new JdbcMemberRepository(dataSource);
    }
}

  • DataSource는 데이터베이스 커넥션을 획득할 때 사용하는 객체다. 스프링 부트는 데이터베이스 커넥션 정보를 바탕으로 DataSource를 생성하고 스프링 빈으로 만들어둔다. 그래서 DI를 받을 수 있다.

  • 개방 폐쇄 원칙(OCP, Open-Closed Principle)
    • 확장에는 열려있고, 수정, 변경에는 닫혀있다.
  • 스프링의 DI(Dependencies Injection)을 사용하면 기존 코드를 전혀 손대지 않고, 설정만으로 구현 클래스를 변경할 수 있다.
  • 데이터를 DB에 저장하므로 스프링 서버를 다시 실행해도 데이터가 안전하게 저장된다.

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