https://github.com/gihyeon6394/sample-spring-jdbc

java (spring) 에서 DB connection을 맺는 방법
https://github.com/gihyeon6394/sample-spring-jdbc

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java (spring) 에서 DB connection을 맺는 방법

• Host: GitHub
• URL: https://github.com/gihyeon6394/sample-spring-jdbc
• Owner: gihyeon6394
• Created: 2023-11-28T03:14:30.000Z (over 1 year ago)
• Default Branch: master
• Last Pushed: 2024-01-05T02:47:19.000Z (over 1 year ago)
• Last Synced: 2025-01-14T03:42:56.351Z (4 months ago)
• Language: Java
• Size: 20.5 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
#### 개발환경

- Java 17

- Spring Boot 3.2

- Gradle 8.4

- MySQL 8.0.28

- lombok

- Spring Data JDBC 3.2.0

- Spring Data JPA 3.2.0

## Java Web Application에서 DB 접근 방법

1. JDBC driver

2. Spring Data JDBC `org.springframework.jdbc.core.JdbcTemplate`

3. Spring Data JDBC `CRUDRepository`

4. Spring Data JPA `JpaRepository`

### 1. JDBC driver

````bash

dependencies {

    ...

    

    runtimeOnly 'com.mysql:mysql-connector-j'

}

````

Java 예제

```java

import org.springframework.stereotype.Component;

import java.sql.*;

import java.util.ArrayList;

import java.util.List;

@Component

public class ConnectDB {

    public List getUserList() throws ClassNotFoundException, SQLException {

        Connection connection = null;

        PreparedStatement statement = null;

        ResultSet resultSet = null;

        List userDtoList = new ArrayList<>();

        try {

            // JDBC 드라이버 로딩

            Class.forName("com.mysql.cj.jdbc.Driver");

            // DB 연결 (가장 느린 부분, DB-WAS network delay)

            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/example_jdbc?serverTimezone=Asia/Seoul", "root", "root");

            // PreparedStatement 생성

            statement = connection.prepareStatement("select id, name from user");

            // 쿼리 실행

            resultSet = statement.executeQuery();

            while (resultSet.next()) {

                long id = resultSet.getLong("id");

                String name = resultSet.getString("name");

                UserDto userDto = new UserDto(id, name);

                userDtoList.add(userDto);

            }

        } catch (ClassNotFoundException e) {

            System.out.println("드라이버 로딩 실패");

            throw e;

        } catch (SQLException e) {

            System.out.println("SQL Error : "+ e.getMessage());

            throw e;

        } finally {

            // 자원 반납

            try {

                resultSet.close();

            } catch (Exception e) {

            }

            try {

                statement.close();

            } catch (Exception e) {

            }

            try {

                connection.close();

            } catch (Exception e) {

            }

        }

        return userDtoList;

    }

}

````

#### 2. Spring Data JDBC `org.springframework.jdbc.core.JdbcTemplate`

````bash

dependencies {

    ...

    runtimeOnly 'com.mysql:mysql-connector-j'

    implementation 'org.springframework.boot:spring-boot-starter-data-jdbc'

}

````

```yaml

spring:

  datasource: # JDBC DB 접속 정보

    driver-class-name: com.mysql.cj.jdbc.Driver

    url: jdbc:mysql://localhost:3306/example_jdbc?serverTimezone=UTC&characterEncoding=UTF-8

    username: root

    password: root

```

Java 예제

```java

import com.example.jdbc.dto.UserDto;

import org.springframework.jdbc.core.JdbcTemplate;

import org.springframework.stereotype.Repository;

import java.util.List;

@Repository // 스프링 빈으로 등록

public class ConnectBySpringDataJdbc {

    private JdbcTemplate jdbcTemplate;

    // Spring이 UserRepository 생성 시 JdbcTemplate을 주입

    public ConnectBySpringDataJdbc(JdbcTemplate jdbcTemplate) {

        this.jdbcTemplate = jdbcTemplate;

    }

    public List getUserList() {

        return jdbcTemplate.query("select id, name from user"

                , (rs, rowNum) -> new UserDto(rs.getLong("id"), rs.getString("name")));

    }

}

````

### 3. Spring Data JDBC `org.springframework.data.repository.CrudRepository`

````bash

dependencies {

    ...

    runtimeOnly 'com.mysql:mysql-connector-j'

    implementation 'org.springframework.boot:spring-boot-starter-data-jdbc'

}

````

Java 예제

```java

import lombok.AllArgsConstructor;

import lombok.Data;

import lombok.NoArgsConstructor;

import lombok.ToString;

import org.springframework.data.relational.core.mapping.Table;

@Data

@AllArgsConstructor

@NoArgsConstructor

@ToString

@Table("User")

public class UserDto {

    private long id;

    private String name;

}

```

```java

import com.example.jdbc.dto.UserDto;

import org.springframework.data.repository.CrudRepository;

public interface UserDtoRepository extends CrudRepository {

}

```

```java

import com.example.jdbc.bySpringJdbc.UserDtoRepository;

import com.example.jdbc.dto.UserDto;

import org.junit.jupiter.api.DisplayName;

import org.junit.jupiter.api.Test;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.test.context.SpringBootTest;

import org.springframework.transaction.annotation.Transactional;

import org.springframework.util.CollectionUtils;

import java.util.List;

import static org.hamcrest.MatcherAssert.assertThat;

import static org.hamcrest.Matchers.is;

import static org.hamcrest.Matchers.notNullValue;

@SpringBootTest

public class JdbcClientTest {

    @Autowired

    private UserDtoRepository userDtoRepository;

    @Test

    @DisplayName("Spring Data JDBCCrudRepository")

    @Transactional

    void db_connenct_with_spring_jdbc_crud_repository() {

        List userDtoList = (List) userDtoRepository.findAll();

        userDtoList.stream().forEach(System.out::println);

        assertThat(userDtoList.size(), is(notNullValue()));

        assertThat(CollectionUtils.isEmpty(userDtoList), is(false));

    }

}

```

### 4. Spring Data JPA `org.springframework.data.jpa.repository.JpaRepository`

````bash

dependencies {

    ...

    runtimeOnly 'com.mysql:mysql-connector-j'

    implementation 'org.springframework.boot:spring-boot-starter-data-jdbc'

    

    annotationProcessor "jakarta.annotation:jakarta.annotation-api"

    annotationProcessor "jakarta.persistence:jakarta.persistence-api"

    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'

}

````

```yaml

spring:

  datasource: # JDBC DB 접속 정보

    driver-class-name: com.mysql.cj.jdbc.Driver

    url: jdbc:mysql://localhost:3306/example_jdbc?serverTimezone=UTC&characterEncoding=UTF-8

    username: root

    password: root

  jpa: # JPA 설정

    hibernate:

      ddl-auto: validate

    show-sql: true # 쿼리 보기

    format-sql: true # 쿼리 포맷팅

    use_sql_comments: true # 쿼리 주석

    type:

      descriptor:

        sql: trace

    properties:

      hibernate:

        dialect: org.hibernate.dialect.MySQL8Dialect # MySQL 버전에 맞는 dialect 설정

```

Java 예제

```java

import jakarta.persistence.*;

import lombok.AllArgsConstructor;

import lombok.Data;

import lombok.NoArgsConstructor;

import lombok.ToString;

@Data

@AllArgsConstructor

@NoArgsConstructor

@ToString

@Entity

@Table(name = "User")

public class UserEntity {

    @Id

    @GeneratedValue(strategy = jakarta.persistence.GenerationType.IDENTITY)

    private long id;

    @Column(name = "name")

    private String name;

}

```

```java

import org.springframework.data.jpa.repository.JpaRepository;

public interface UserEntityRepository extends JpaRepository {

}

```

```java

import com.example.jdbc.bySpringJdbc.springDataJpa.UserEntity;

import com.example.jdbc.bySpringJdbc.springDataJpa.UserEntityRepository;

import org.junit.jupiter.api.DisplayName;

import org.junit.jupiter.api.Test;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.test.context.SpringBootTest;

import org.springframework.util.CollectionUtils;

import java.util.List;

import static org.hamcrest.MatcherAssert.assertThat;

import static org.hamcrest.Matchers.is;

import static org.hamcrest.Matchers.notNullValue;

@SpringBootTest

public class JdbcClientTest {

    @Autowired

    private UserEntityRepository userRepository;

    @Test

    @DisplayName("Spring Data JPAJpaRepository")

    void db_connenct_with_spring_jpa_jpa_repository() {

        List userEntityList = userRepository.findAll();

        userEntityList.stream().forEach(System.out::println);

        assertThat(userEntityList.size(), is(notNullValue()));

        assertThat(CollectionUtils.isEmpty(userEntityList), is(false));

    }

}

```