jpa-patterns

JPA/Hibernate patterns

For data modeling, Repository layer implementation, and performance tuning in Spring Boot.

When to activate

• Designing JPA entities and table mappings
• Defining associations (@OneToMany, @ManyToOne, @ManyToMany)
• Optimizing queries (preventing N+1 issues, fetch strategies, projections)
• Configuring transactions, auditing, or soft deletes
• Setting up pagination, sorting, or custom Repository methods
• Tuning the connection pool (HikariCP) or second-level caching

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 {}

Associations and preventing N+1 issues

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

• Use lazy loading by default; in queries use JOIN FETCH
• Avoid using EAGERon collections; use DTO projections on 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 pattern

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

• Add @Transactional annotation on Service methods
• Use @Transactional(readOnly = true) on read paths for optimization
• Choose propagation carefully; avoid long 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 together with sorting.

Indexing and performance

• Add indexes for frequently used filters (status、slug, foreign keys)
• Use composite indexes matching query patterns (status, created_at）
• Avoid using select *; only project the required columns
• Use saveAll and hibernate.jdbc.batch_size for batch writes

Connection pool (HikariCP)

Recommended property configuration:

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

• The first-level cache is based on the EntityManager; avoid retaining entities across transactions
• For read-heavy, write-light entities, carefully consider the second-level cache; verify the eviction strategy

Database migrations (Migrations)

• Use Flyway or Liquibase; never rely on Hibernate auto DDL in production
• Keep migration scripts idempotent and incremental; avoid dropping columns without a plan

Testing data access

• Prefer using @DataJpaTest with Testcontainers to mirror production
• Assert SQL efficiency through logs: set logging.level.org.hibernate.SQL=DEBUG and for parameter values logging.level.org.hibernate.orm.jdbc.bind=TRACE

Remember: keep entities lean, query intent clear, and transactions short. Prevent N+1 issues through fetch strategies and projections, and index read/write paths.