jpa-patterns

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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 パターン

Spring Bootでのデータモデリング、リポジトリ、パフォーマンスチューニングに使用します。

## エンティティ設計

```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;
}
```

監査を有効化:
```java
@Configuration
@EnableJpaAuditing
class JpaConfig {}
```

## リレーションシップとN+1防止

```java
@OneToMany(mappedBy = "market", cascade = CascadeType.ALL, orphanRemoval = true)
private List<PositionEntity> positions = new ArrayList<>();
```

- デフォルトで遅延ロード。必要に応じてクエリで `JOIN FETCH` を使用
- コレクションでは `EAGER` を避け、読み取りパスにはDTOプロジェクションを使用

```java
@Query("select m from MarketEntity m left join fetch m.positions where m.id = :id")
Optional<MarketEntity> findWithPositions(@Param("id") Long id);
```

## リポジトリパターン

```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);
}
```

- 軽量クエリにはプロジェクションを使用:
```java
public interface MarketSummary {
  Long getId();
  String getName();
  MarketStatus getStatus();
}
Page<MarketSummary> findAllBy(Pageable pageable);
```

## トランザクション

- サービスメソッドに `@Transactional` を付ける
- 読み取りパスを最適化するために `@Transactional(readOnly = true)` を使用
- 伝播を慎重に選択。長時

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  "skill": "imp-4fbfda99-8f34-4e4e-9d9b-5d145430ce4f",
  "messages": [{ "role": "user", "content": "…" }]
}

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