# Spring Boot Data Access

> Best practices for JPA, Hibernate, and Database interactions in Spring Boot. Use when implementing JPA entities, repositories, or database access in Spring Boot. (triggers: **/*Repository.java, **/*Entity.java, jpa-repository, entity-graph, transactional, n-plus-1)

- Skill: `comeonoliver/spring-boot-data-access` (Agent Skill)
- Install (CLI): `npx skillmds@latest add comeonoliver/spring-boot-data-access`
- Raw SKILL.md: https://api.skillmd.com/api/skills/comeonoliver/spring-boot-data-access/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- Author: ComeOnOliver (https://skillmd.com/u/comeonoliver)
- Updated: 2026-09-08
- Page: https://skillmd.com/skills/comeonoliver/spring-boot-data-access

---


# Spring Boot Data Access

## **Priority: P0**

## Implementation Guidelines

### JPA & Hibernate (Spring Data JPA)

- **Read-Only**: Default to **`@Transactional(readOnly = true)`** on Services to optimize DB resources.
- **Projections**: Use **`Java Records`** for **Read-Only** query results. Avoid fetching full **`@Entity`** objects when not necessary.
- **Pagination**: ALWAYS use **`Pageable`** and **`Slice`** (or `Page`) to prevent loading massive datasets.
- **Spring Data**: Prefer **`JpaRepository`** and **`Query methods`**. Use **`@Query`** with JPQL for complex logic. Use Flyway or Liquibase for migrations; never use `spring.jpa.hibernate.ddl-auto=create` (`ddl-auto`) in production.

### Query & Transaction Optimization

- **N+1 Problem**: Fix **`N+1`** selects using **`JOIN FETCH`** (JPQL) or **`@EntityGraph`**.
- **Open-In-View**: Set `spring.jpa.open-in-view=false` in **`application.yaml`**.
- **Bulk Operations**: Use **`@Modifying`** with `@Query` for updates/deletes to bypass EntityManager overhead.
- **Connection Pool**: Configure **`HikariCP`** with explicit `maximum-pool-size`. Tune Hikari pool-size based on expected concurrent queries.

## Anti-Patterns

- **No N+1 Selects**: Use **`JOIN FETCH`** or **`@EntityGraph`** instead of lazy-loading in loops.
- **Entity Inflation**: Don't use `@Data` (Lombok) on Entities as it breaks Proxy and `hashCode`/`equals` performance.
- **Transactional Leak**: Don't put `@Transactional` on public `Repository` methods if the `Service` is already transactional.
- **Raw SQL**: Avoid native SQL unless JPQL/Criteria API is insufficient.

## References

- [Implementation Examples](references/implementation.md)