JPA/Hibernate Patterns

Overview

Best practices for data modeling, repository design, and performance tuning with JPA/Hibernate in Spring Boot. Covers entity design, relationship mapping, N+1 prevention, transactions, pagination, indexing, connection pooling, caching, and testing.

Relationships & N+1 Prevention

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

Key rules:

• Default to lazy loading; use JOIN FETCH 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);
}

Lightweight queries with projections:

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
• Keep transactions short; 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-based pagination, include id > :lastId in JPQL with ordering.

Indexing & Performance

• Index common filters: status, slug, foreign keys
• 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)

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:

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

Caching

• 1st-level cache is per EntityManager; don't keep 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

Testing Data Access

• Prefer @DataJpaTest with Testcontainers to mirror production
• Assert SQL efficiency:
  • logging.level.org.hibernate.SQL=DEBUG
  • logging.level.org.hibernate.orm.jdbc.bind=TRACE

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