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* docs: add Chinese versions docs * update --------- Co-authored-by: neo <neo.dowithless@gmail.com>
146 lines
4.0 KiB
Markdown
146 lines
4.0 KiB
Markdown
---
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name: jpa-patterns
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description: Spring Boot中的JPA/Hibernate实体设计、关系、查询优化、事务、审计、索引、分页和连接池模式。
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---
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# JPA/Hibernate 模式
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用于 Spring Boot 中的数据建模、存储库和性能调优。
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## 实体设计
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```java
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@Entity
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@Table(name = "markets", indexes = {
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@Index(name = "idx_markets_slug", columnList = "slug", unique = true)
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})
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@EntityListeners(AuditingEntityListener.class)
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public class MarketEntity {
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@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
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private Long id;
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@Column(nullable = false, length = 200)
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private String name;
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@Column(nullable = false, unique = true, length = 120)
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private String slug;
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@Enumerated(EnumType.STRING)
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private MarketStatus status = MarketStatus.ACTIVE;
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@CreatedDate private Instant createdAt;
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@LastModifiedDate private Instant updatedAt;
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}
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```
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启用审计：
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```java
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@Configuration
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@EnableJpaAuditing
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class JpaConfig {}
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```
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## 关联关系和 N+1 预防
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```java
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@OneToMany(mappedBy = "market", cascade = CascadeType.ALL, orphanRemoval = true)
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private List<PositionEntity> positions = new ArrayList<>();
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```
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* 默认使用延迟加载；需要时在查询中使用 `JOIN FETCH`
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* 避免在集合上使用 `EAGER`；对于读取路径使用 DTO 投影
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```java
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@Query("select m from MarketEntity m left join fetch m.positions where m.id = :id")
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Optional<MarketEntity> findWithPositions(@Param("id") Long id);
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```
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## 存储库模式
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```java
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public interface MarketRepository extends JpaRepository<MarketEntity, Long> {
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Optional<MarketEntity> findBySlug(String slug);
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@Query("select m from MarketEntity m where m.status = :status")
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Page<MarketEntity> findByStatus(@Param("status") MarketStatus status, Pageable pageable);
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}
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```
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* 使用投影进行轻量级查询：
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```java
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public interface MarketSummary {
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Long getId();
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String getName();
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MarketStatus getStatus();
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}
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Page<MarketSummary> findAllBy(Pageable pageable);
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```
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## 事务
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* 使用 `@Transactional` 注解服务方法
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* 对读取路径使用 `@Transactional(readOnly = true)` 以进行优化
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* 谨慎选择传播行为；避免长时间运行的事务
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```java
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@Transactional
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public Market updateStatus(Long id, MarketStatus status) {
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MarketEntity entity = repo.findById(id)
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.orElseThrow(() -> new EntityNotFoundException("Market"));
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entity.setStatus(status);
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return Market.from(entity);
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}
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```
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## 分页
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```java
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PageRequest page = PageRequest.of(pageNumber, pageSize, Sort.by("createdAt").descending());
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Page<MarketEntity> markets = repo.findByStatus(MarketStatus.ACTIVE, page);
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```
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对于类似游标的分页，在 JPQL 中包含 `id > :lastId` 并配合排序。
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## 索引和性能
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* 为常用过滤器添加索引（`status`、`slug`、外键）
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* 使用与查询模式匹配的复合索引（`status, created_at`）
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* 避免 `select *`；仅投影需要的列
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* 使用 `saveAll` 和 `hibernate.jdbc.batch_size` 进行批量写入
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## 连接池 (HikariCP)
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推荐属性：
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```
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spring.datasource.hikari.maximum-pool-size=20
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spring.datasource.hikari.minimum-idle=5
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spring.datasource.hikari.connection-timeout=30000
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spring.datasource.hikari.validation-timeout=5000
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```
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对于 PostgreSQL LOB 处理，添加：
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```
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spring.jpa.properties.hibernate.jdbc.lob.non_contextual_creation=true
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```
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## 缓存
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* 一级缓存是每个 EntityManager 的；避免在事务之间保持实体
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* 对于读取频繁的实体，谨慎考虑二级缓存；验证驱逐策略
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## 迁移
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* 使用 Flyway 或 Liquibase；切勿在生产中依赖 Hibernate 自动 DDL
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* 保持迁移的幂等性和可添加性；避免无计划地删除列
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## 测试数据访问
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* 首选使用 Testcontainers 的 `@DataJpaTest` 来镜像生产环境
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* 使用日志断言 SQL 效率：设置 `logging.level.org.hibernate.SQL=DEBUG` 和 `logging.level.org.hibernate.orm.jdbc.bind=TRACE` 以查看参数值
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**请记住**：保持实体精简，查询有针对性，事务简短。通过获取策略和投影来预防 N+1 问题，并根据读写路径建立索引。
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