• NoArgConstructor, Getter, Setter ⇒ kotlin 기본제공
• AllArgConstructor ⇒ named argument
• JPA를 사용한다면 변경될 수 있는 프로퍼티를 var로 선언해주어야 한다.

// java 
@NoArgsConstructor
@AllArgsConstructor
@Getter
@Builder
@Entity
@Table(name = "todos")
public class Todo {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "title")
    private String title;

    @Lob
    @Column(name = "description")
    private String description;

    @Column(name = "done")
    private Boolean done;

    @Column(name = "created_at")
    private LocalDateTime createdAt;

    @Column(name = "updated_at")
    private LocalDateTime updatedAt;

    public void update(String title, String description, Boolean done) {
        this.title = title;
        this.description = description;
        this.done = done != null && done;
        this.updatedAt = LocalDateTime.now();
    }
}

// kotlin
@Entity
@Table(name = "todos")
class Todo(
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    val id: Long? = 0,

    @Column(name = "title")
    var title: String,

    @Lob
    @Column(name = "description")
    var description: String,

    @Column(name = "done")
    var done: Boolean,

    @Column(name = "created_at")
    var createdAt: LocalDateTime,

    @Column(name = "updated_at")
    var updatedAt: LocalDateTime? = null,
) {

    fun update(title: String, description: String, done: Boolean) {
        this.title = title
        this.description = description
        this.done = done
        this.updatedAt = LocalDateTime.now()
    }
}

TodoRepository

• Optional ⇒ nullable

// java
public interface TodoRepository extends JpaRepository<Todo, Long> {

    Optional<List<Todo>> findAllByDoneIsFalseOrderByIdDesc();
}

// kotlin
interface TodoRepository : JpaRepository<Todo, Long> {

    fun findAllByDoneIsFalseOrderByIdDesc(): List<Todo>?
}