jpa-patterns

# JPA/Hibernate Patterns Use for data modeling, repositories, and performance tuning in Spring Boot. ## Entity Design ```java @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; } ``` Enable auditing: ```java @Configuration @EnableJpaAuditing class JpaConfig {} ``` ## Relationships and N+1 Prevention ```java @OneToMany(mappedBy = "market", cascade = CascadeType.ALL, orphanRemoval = true) private List<PositionEntity> positions = new ArrayList<>(); ``` - Default to lazy loading; use `JOIN FETCH` in queries when needed - Avoid `EAGER` on collections; use DTO projections for read paths ```java @Query("select m from MarketEntity m left join fetch m.positions where m.id = :id") Optional<MarketEntity> findWithPositions(@Param("id") Long id); ``` ## Repository Patterns ```java public interface MarketRepository extends JpaRepository<MarketEntity, Long> { Optional<MarketEntity> findBySlu...