Jpa Patterns

@Entity@Table(name = "markets", indexes = {  @Index(name = "idx_markets_slug", columnList = "slug", unique = true)})@EntityListeners(AuditingEntityListener.class)public class MarketEntity {  @Id @GeneratedValue(strategy = GenerationType.IDENTITY)  private Long id;
  @Column(nullable = false, length = 200)  private String name;
  @Column(nullable = false, unique = true, length = 120)  private String slug;
  @Enumerated(EnumType.STRING)  private MarketStatus status = MarketStatus.ACTIVE;
  @CreatedDate private Instant createdAt;  @LastModifiedDate private Instant updatedAt;}

@Configuration@EnableJpaAuditingclass JpaConfig {}

@OneToMany(mappedBy = "market", cascade = CascadeType.ALL, orphanRemoval = true)private List<PositionEntity> positions = new ArrayList<>();

@Query("select m from MarketEntity m left join fetch m.positions where m.id = :id")Optional<MarketEntity> findWithPositions(@Param("id") Long id);

public interface MarketRepository extends JpaRepository<MarketEntity, Long> {  Optional<MarketEntity> findBySlug(String slug);
  @Query("select m from MarketEntity m where m.status = :status")  Page<MarketEntity> findByStatus(@Param("status") MarketStatus status, Pageable pageable);}

public interface MarketSummary {  Long getId();  String getName();  MarketStatus getStatus();}Page<MarketSummary> findAllBy(Pageable pageable);

@Transactionalpublic Market updateStatus(Long id, MarketStatus status) {  MarketEntity entity = repo.findById(id)      .orElseThrow(() -> new EntityNotFoundException("Market"));  entity.setStatus(status);  return Market.from(entity);}

PageRequest page = PageRequest.of(pageNumber, pageSize, Sort.by("createdAt").descending());Page<MarketEntity> markets = repo.findByStatus(MarketStatus.ACTIVE, page);