Spring Data JPA 高级指南：关联映射、N+1 与性能优化

Tue, 01 Sep 2026 10:00:00 +0800

Spring Data JPA 是 Spring 生态中最主流的 ORM 封装方案，它屏蔽了绝大多数 JDBC 样板代码，让开发者以声明式方式操作数据库。然而，简单 CURD 与生产级应用之间存在巨大的性能鸿沟：一次不小心的 EAGER 加载可能拖垮整个接口，一个缺失的索引会让分页查询变成全表扫描。本文从实体映射、关联设计、N+1 根治、批量写入、分页策略、审计、动态查询、二级缓存到事务传播，逐层递进，给出可直接落地的代码与配置。

09. Spring Data MongoDB 实战

Fri, 14 Aug 2026 12:09:00 +0800

Spring Data MongoDB 是 Spring 生态中对 MongoDB 的官方支持，提供了 Repository 接口和 MongoTemplate 两种操作模式。本文覆盖配置、基础 CRUD、复杂查询、聚合与事务。

1. 配置

# application.yml
spring:
 data:
 mongodb:
 uri: mongodb://user:pass@mongo1:27017,mongo2:27017/mydatabase?replicaSet=rs0
 # 或:
 # host: localhost
 # port: 27017
 # database: mydatabase
 # username: user
 # password: pass

<dependency>
 <groupId>org.springframework.boot</groupId>
 <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

2. 实体映射

@Document(collection = "products")
@CompoundIndex(name = "category_price", def = "{'category': 1, 'price': -1}")
public class Product {
 @Id
 private String id; // 映射 _id

 private String name;
 private String category;
 private BigDecimal price;
 private int stock;

 @Field("created_at")
 private Instant createdAt;

 @DBRef
 private Supplier supplier; // 引用（慎用，性能差）

 // 嵌套文档
 private List<Review> reviews;
}

public record Review(String userId, int rating, String comment, Instant date) {}

3. Repository 接口

public interface ProductRepository extends MongoRepository<Product, String> {

 // 自动派生查询
 List<Product> findByCategoryAndPriceLessThan(String category, BigDecimal price);

 // 模糊搜索（正则）
 List<Product> findByNameContainingIgnoreCase(String name);

 // 排序分页
 Page<Product> findByCategoryOrderByPriceDesc(String category, Pageable pageable);

 // @Query 自定义
 @Query("{ 'category': ?0, 'price': { $gte: ?1, $lte: ?2 } }")
 List<Product> findByPriceRange(String category, BigDecimal min, BigDecimal max);

 // 聚合统计
 @Aggregation(pipeline = {
 "{ $match: { category: ?0 } }",
 "{ $group: { _id: null, avgPrice: { $avg: '$price' }, totalStock: { $sum: '$stock' } } }"
 })
 ProductStats getStatsByCategory(String category);
}

4. MongoTemplate

@Service
public class ProductService {
 @Autowired private MongoTemplate mongoTemplate;

 public List<Product> search(String keyword, String category) {
 Query query = new Query();

 // 动态条件
 if (StringUtils.hasText(keyword)) {
 query.addCriteria(Criteria.where("name")
 .regex(keyword, "i"));
 }
 if (StringUtils.hasText(category)) {
 query.addCriteria(Criteria.where("category").is(category));
 }

 query.with(Sort.by(Sort.Direction.DESC, "createdAt"));
 query.limit(20);

 return mongoTemplate.find(query, Product.class);
 }

 // 批量更新
 public void updateStockBatch(Map<String, Integer> stockChanges) {
 BulkOperations bulkOps = mongoTemplate.bulkOps(
 BulkOperations.BulkMode.UNORDERED, Product.class);

 stockChanges.forEach((id, qty) -> {
 Query query = Query.query(Criteria.where("_id").is(id));
 Update update = new Update().inc("stock", qty);
 bulkOps.updateOne(query, update);
 });

 bulkOps.execute();
 }

 // 聚合管道
 public List<Document> getCategoryRevenue() {
 Aggregation agg = Aggregation.newAggregation(
 Aggregation.match(Criteria.where("status").is("completed")),
 Aggregation.unwind("items"),
 Aggregation.group("items.category")
 .sum(ArithmeticOperators.Multiply.valueOf("items.price")
 .multiplyBy("items.quantity")).as("revenue"),
 Aggregation.sort(Sort.Direction.DESC, "revenue")
 );

 return mongoTemplate.aggregate(agg, "orders", Document.class)
 .getMappedResults();
 }
}

5. 事务

@Service
public class OrderService {
 @Autowired private MongoTemplate mongoTemplate;
 @Autowired private MongoTransactionManager transactionManager;

 @Transactional
 public void createOrder(OrderRequest request) {
 // 扣减库存
 mongoTemplate.updateFirst(
 Query.query(Criteria.where("sku").is(request.sku())),
 new Update().inc("stock", -request.qty()),
 Product.class
 );

 // 创建订单
 Order order = new Order(request);
 mongoTemplate.save(order);
 }
}

Spring Data on PlumePHP