Jpa Patterns

1---2name: jpa-patterns3description: JPA/Hibernate patterns for entity design, relationships, query optimization, transactions, auditing, indexing, pagination, and pooling in Spring Boot.4origin: ECC5---6 7# JPA/Hibernate Patterns8 9Use for data modeling, repositories, and performance tuning in Spring Boot.10 11## When to Activate12 13- Designing JPA entities and table mappings14- Defining relationships (@OneToMany, @ManyToOne, @ManyToMany)15- Optimizing queries (N+1 prevention, fetch strategies, projections)16- Configuring transactions, auditing, or soft deletes17- Setting up pagination, sorting, or custom repository methods18- Tuning connection pooling (HikariCP) or second-level caching19 20## Entity Design21 22```java23@Entity24@Table(name = "markets", indexes = {25  @Index(name = "idx_markets_slug", columnList = "slug", unique = true)26})27@EntityListeners(AuditingEntityListener.class)28public class MarketEntity {29  @Id @GeneratedValue(strategy = GenerationType.IDENTITY)30  private Long id;31 32  @Column(nullable = false, length = 200)33  private String name;34 35  @Column(nullable = false, unique = true, length = 120)36  private String slug;37 38  @Enumerated(EnumType.STRING)39  private MarketStatus status = MarketStatus.ACTIVE;40 41  @CreatedDate private Instant createdAt;42  @LastModifiedDate private Instant updatedAt;43}44```45 46Enable auditing:47```java48@Configuration49@EnableJpaAuditing50class JpaConfig {}51```52 53## Relationships and N+1 Prevention54 55```java56@OneToMany(mappedBy = "market", cascade = CascadeType.ALL, orphanRemoval = true)57private List<PositionEntity> positions = new ArrayList<>();58```59 60- Default to lazy loading; use `JOIN FETCH` in queries when needed61- Avoid `EAGER` on collections; use DTO projections for read paths62 63```java64@Query("select m from MarketEntity m left join fetch m.positions where m.id = :id")65Optional<MarketEntity> findWithPositions(@Param("id") Long id);66```67 68## Repository Patterns69 70```java71public interface MarketRepository extends JpaRepository<MarketEntity, Long> {72  Optional<MarketEntity> findBySlug(String slug);73 74  @Query("select m from MarketEntity m where m.status = :status")75  Page<MarketEntity> findByStatus(@Param("status") MarketStatus status, Pageable pageable);76}77```78 79- Use projections for lightweight queries:80```java81public interface MarketSummary {82  Long getId();83  String getName();84  MarketStatus getStatus();85}86Page<MarketSummary> findAllBy(Pageable pageable);87```88 89## Transactions90 91- Annotate service methods with `@Transactional`92- Use `@Transactional(readOnly = true)` for read paths to optimize93- Choose propagation carefully; avoid long-running transactions94 95```java96@Transactional97public Market updateStatus(Long id, MarketStatus status) {98  MarketEntity entity = repo.findById(id)99      .orElseThrow(() -> new EntityNotFoundException("Market"));100  entity.setStatus(status);101  return Market.from(entity);102}103```104 105## Pagination106 107```java108PageRequest page = PageRequest.of(pageNumber, pageSize, Sort.by("createdAt").descending());109Page<MarketEntity> markets = repo.findByStatus(MarketStatus.ACTIVE, page);110```111 112For cursor-like pagination, include `id > :lastId` in JPQL with ordering.113 114## Indexing and Performance115 116- Add indexes for common filters (`status`, `slug`, foreign keys)117- Use composite indexes matching query patterns (`status, created_at`)118- Avoid `select *`; project only needed columns119- Batch writes with `saveAll` and `hibernate.jdbc.batch_size`120 121## Connection Pooling (HikariCP)122 123Recommended properties:124```125spring.datasource.hikari.maximum-pool-size=20126spring.datasource.hikari.minimum-idle=5127spring.datasource.hikari.connection-timeout=30000128spring.datasource.hikari.validation-timeout=5000129```130 131For PostgreSQL LOB handling, add:132```133spring.jpa.properties.hibernate.jdbc.lob.non_contextual_creation=true134```135 136## Caching137 138- 1st-level cache is per EntityManager; avoid keeping entities across transactions139- For read-heavy entities, consider second-level cache cautiously; validate eviction strategy140 141## Migrations142 143- Use Flyway or Liquibase; never rely on Hibernate auto DDL in production144- Keep migrations idempotent and additive; avoid dropping columns without plan145 146## Testing Data Access147 148- Prefer `@DataJpaTest` with Testcontainers to mirror production149- Assert SQL efficiency using logs: set `logging.level.org.hibernate.SQL=DEBUG` and `logging.level.org.hibernate.orm.jdbc.bind=TRACE` for parameter values150 151**Remember**: Keep entities lean, queries intentional, and transactions short. Prevent N+1 with fetch strategies and projections, and index for your read/write paths.