Kotlin Spring

For this project, I chose to use PostgreSQL because it's familiar and reliable. Combining Kotlin with Spring Boot allows me to write some incredibly expressive code.

A Spring Boot properties file is used to configure the database connection, with the password supplied through an environment variable.

spring.datasource.url=jdbc:postgresql://localhost:5432/postgres
spring.datasource.username=postgres
spring.datasource.password=${POSTGRES_PASSWORD}
spring.datasource.driver-class-name=org.postgresql.Driver

Kotlin dataclasses are annotated with Spring Data JDBC to behave as an ORM.

@Table("member")
data class Member(
    var username: String,
    val origin: String = "GITHUB",
    @Id var id: Int? = null,
)

This allows to use Spring Data's magical derived query methods in addition to built-in CrudRepository operations.

interface MemberRepository : CrudRepository<Member, Int> {
    fun findByUsernameAndOrigin(username: String, origin: String): Member?
}

The MemberService uses Spring's dependency injection to get an instance of MemberRepository and SessionData.

@Service
class MemberService(val memberRepository: MemberRepository) {
    fun ensureMemberExists(currentUser: SessionData) {
        val member = memberRepository.findByUsernameAndOrigin(currentUser.username, "GITHUB")

        if (member == null) {
            memberRepository.save(Member(currentUser.username))
        }
    }
}