walterfan/lazy-ai-primer/jpa-patterns

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JPA/Hibernate patterns for entity design, relationships, query optimization, transactions, auditing, indexing, pagination, and pooling in Spring Boot.

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npx vskill@latest install walterfan/lazy-ai-primer/jpa-patterns

SKILL.md

The same SKILL.md was published earlier as jamkris/everything-gemini-code/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> 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:
java
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
java
@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

java
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.

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