Spring Boot 데이터베이스 연동: Spring Data JPA 활용하기

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <scope>runtime</scope>
</dependency>

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
    runtimeOnly 'com.h2database:h2'
}

# H2 인메모리 DB 설정 예시
spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
 
# JPA 상세 설정
spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true

@Entity
@Getter @Setter
public class User {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    @Column(nullable = false)
    private String name;
    
    private String email;
}

public interface UserRepository extends JpaRepository<User, Long> {
    // 메소드 이름만으로 쿼리 생성 가능
    Optional<User> findByEmail(String email);
}

@Service
@RequiredArgsConstructor
public class UserService {
    private final UserRepository userRepository;
 
    @Transactional
    public Long join(User user) {
        userRepository.save(user);
        return user.getId();
    }
}