jpa-patterns

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---
name: jpa-patterns
description: Spring Boot中的JPA/Hibernate模式，用于实体设计、关系处理、查询优化、事务管理、审计、索引、分页和连接池。
origin: ECC
---

# JPA/Hibernate 模式

用于 Spring Boot 中的数据建模、存储库和性能调优。

## 何时激活

* 设计 JPA 实体和表映射时
* 定义关系时 (@OneToMany, @ManyToOne, @ManyToMany)
* 优化查询时 (N+1 问题预防、获取策略、投影)
* 配置事务、审计或软删除时
* 设置分页、排序或自定义存储库方法时
* 调整连接池 (HikariCP) 或二级缓存时

## 实体设计

```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;
}
```

启用审计：

```java
@Configuration
@EnableJpaAuditing
class JpaConfig {}
```

## 关联关系和 N+1 预防

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

* 默认使用延迟加载；需要时在查询中使用 `JOIN FETCH`
* 避免在集合上使用 `EAGER`；对于读取路径使用 DTO 投影

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

## 存储库模式

```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);
}
```

* 使用投影进行轻量级查询：

```java
public interface MarketSummary {
  Long getId();
  String getName();
  MarketStatus getStatus();
}
Page<MarketSummary> findAllBy(Pageable pageable);
```

## 事务

* 使用 `@Transactional` 注解服务方法
* 对读取路径使用 `@Transactional(readOnly = true)` 以进行优化

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  "skill": "imp-5e0d92f3-8fb6-42ab-a1da-de9d7a4ae973",
  "messages": [{ "role": "user", "content": "…" }]
}

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