#064Lazy-Loaded JPA Relationship Causes N+1 Queries
spring.hardSPRING
1@Entity
2public class Order {
3 @Id
4 private Long id;
5
6 @ManyToOne(fetch = FetchType.LAZY)
7 private Customer customer;
8}
9
10@Service
11public class OrderReportService {
12 public List<String> customerNames() {
13 List<Order> orders = orderRepository.findAll();
14 List<String> names = new ArrayList<>();
15 for (Order order : orders) {
16 names.add(order.getCustomer().getName());
17 }
18 return names;
19 }
20}
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#064PracticeHard28 min · 200 XP
Lazy-Loaded JPA Relationship Causes N+1 Queries
Listing all orders with their customer names issues one extra query per order instead of a single join.
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