JPA/Hibernate Patterns

Use for data modeling, repositories, and performance tuning in Spring Boot.

Entity Design

@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:

@Configuration @EnableJpaAuditing class JpaConfig {}

Relationships and N+1 Prevention

@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

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

Repository Patterns

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); }

• Use projections for lightweight queries:

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

Transactions

• Annotate service methods with @Transactional

• Use @Transactional(readOnly = true) for read paths to optimize

• Choose propagation carefully; avoid long-running transactions

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

Pagination

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

For cursor-like pagination, include id > :lastId in JPQL with ordering.

Indexing and Performance

• Add indexes for common filters (status , slug , foreign keys)

• Use composite indexes matching query patterns (status, created_at )

• Avoid select * ; project only needed columns

• Batch writes with saveAll and hibernate.jdbc.batch_size

Connection Pooling (HikariCP)

Recommended properties:

spring.datasource.hikari.maximum-pool-size=20 spring.datasource.hikari.minimum-idle=5 spring.datasource.hikari.connection-timeout=30000 spring.datasource.hikari.validation-timeout=5000

For PostgreSQL LOB handling, add:

spring.jpa.properties.hibernate.jdbc.lob.non_contextual_creation=true

Caching

• 1st-level cache is per EntityManager; avoid keeping entities across transactions

• For read-heavy entities, consider second-level cache cautiously; validate eviction strategy

Migrations

• Use Flyway or Liquibase; never rely on Hibernate auto DDL in production

• Keep migrations idempotent and additive; avoid dropping columns without plan

Testing Data Access

• Prefer @DataJpaTest with Testcontainers to mirror production

• Assert SQL efficiency using logs: set logging.level.org.hibernate.SQL=DEBUG and logging.level.org.hibernate.orm.jdbc.bind=TRACE for parameter values

Remember: Keep entities lean, queries intentional, and transactions short. Prevent N+1 with fetch strategies and projections, and index for your read/write paths.