jpa-patterns

name jpa-patterns description JPA/Hibernate patterns for entity design, relationships, query optimization, transactions, auditing, indexing, pagination, and pooling in Spring Boot. origin ECC JPA/Hibernate Patterns Use for data modeling, repositories, and performance tuning in Spring Boot. When to Activate Designing JPA entities and table mappings Defining relationships (@OneToMany, @ManyToOne, @ManyToMany) Optimizing queries (N+1 prevention, fetch strategies, projections) Configuring transactions, auditing, or soft deletes Setting up pagination, sorting, or custom repository methods Tuning connection pooling (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 {} 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 distinct m from MarketEntity m left join fetch m.positions where m.id = :id") Optional<MarketEntity> findWithPositions ( @Param("id") Long id) ; Note: DISTINCT is required when fetch-joining a one-to-many collection — without it, the root entity is duplicated once per child row in the result set. For single-result queries ( findById ) the duplication is harmless, but for list queries it produces duplicate root objects. Hibernate 6+ applies de-duplication automatically in some cases, but explicit DISTINCT keeps behavior portable and clear. 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.