Initial: Claude config with agents, skills, commands, rules and scripts

skills/jpa-patterns/SKILL.md

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+---
+name: jpa-patterns
+description: JPA/Hibernate patterns for entity design, relationships, query optimization, transactions, auditing, indexing, pagination, and pooling in Spring Boot.
+---
+
+# 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
+
+```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.