2nd/10_Wiki/Topic_Programming/Architecture/Spring Framework.md

---
id: wiki-2026-0508-spring-framework
title: Spring Framework
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [Spring, Spring Boot, Spring Core]
duplicate_of: none
source_trust_level: A
confidence_score: 0.9
verification_status: applied
tags: [java, framework, dependency-injection, spring-boot]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
  language: java
  framework: spring-boot
---

# Spring Framework

## 매 한 줄
> **"매 Java enterprise 의 IoC container — 매 Beans, AOP, MVC, Boot 의 ecosystem"**. Rod Johnson (2003) 의 J2EE 대체. 2026 현재 Spring Boot 3.4 (Java 21+, virtual threads, AOT/GraalVM native) 가 매 backend Java 의 de-facto.

## 매 핵심

### 매 IoC / DI
- **ApplicationContext**: 매 Bean 의 lifecycle 관리.
- **`@Component`, `@Service`, `@Repository`, `@Controller`**: 매 stereotype.
- **Constructor injection**: 매 권장 (final field, immutability).

### 매 modules
- **Spring Core**: IoC, DI, Resource, SpEL.
- **Spring MVC / WebFlux**: HTTP (Servlet vs reactive).
- **Spring Data**: JPA, MongoDB, Redis repository abstraction.
- **Spring Security**: Auth (OAuth2, JWT, OIDC).
- **Spring Boot**: 매 auto-configuration, embedded Tomcat/Netty.

### 매 응용
1. REST API backend (Boot + Web + Data JPA).
2. Reactive microservice (WebFlux + R2DBC).
3. Batch job (Spring Batch).

## 💻 패턴

### Spring Boot 3.4 application
```java
@SpringBootApplication
public class App {
    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }
}
```

### Constructor injection 의 service
```java
@Service
public class OrderService {
    private final OrderRepository repo;
    private final PaymentClient payments;

    public OrderService(OrderRepository repo, PaymentClient payments) {
        this.repo = repo;
        this.payments = payments;
    }

    public Order place(NewOrder cmd) {
        var charge = payments.charge(cmd.amount());
        return repo.save(new Order(cmd, charge.id()));
    }
}
```

### REST controller (Java 21 records)
```java
@RestController
@RequestMapping("/orders")
public class OrderController {
    private final OrderService service;
    public OrderController(OrderService s) { this.service = s; }

    @PostMapping
    public ResponseEntity<Order> create(@Valid @RequestBody NewOrder cmd) {
        return ResponseEntity.status(201).body(service.place(cmd));
    }
}

public record NewOrder(@NotBlank String sku, @Positive long amount) {}
```

### Spring Data JPA repository
```java
public interface OrderRepository extends JpaRepository<Order, Long> {
    List<Order> findByCustomerIdAndCreatedAfter(Long customerId, Instant after);
}
```

### Configuration properties
```java
@ConfigurationProperties("payments")
public record PaymentsConfig(String url, Duration timeout, String apiKey) {}
```

```yaml
# application.yml
payments:
  url: https://api.stripe.com
  timeout: 5s
  api-key: ${STRIPE_KEY}
```

### Virtual threads (Boot 3.2+, Java 21)
```yaml
spring:
  threads:
    virtual:
      enabled: true
```

### WebFlux reactive endpoint
```java
@GetMapping("/stream")
public Flux<Event> stream() {
    return eventRepo.findAll().delayElements(Duration.ofMillis(100));
}
```

### Test (slice)
```java
@WebMvcTest(OrderController.class)
class OrderControllerTest {
    @Autowired MockMvc mvc;
    @MockBean OrderService service;

    @Test
    void createsOrder() throws Exception {
        when(service.place(any())).thenReturn(new Order(1L, "sku", 100));
        mvc.perform(post("/orders").contentType(APPLICATION_JSON)
            .content("""{"sku":"sku","amount":100}"""))
           .andExpect(status().isCreated());
    }
}
```

## 매 결정 기준
| 상황 | Approach |
|---|---|
| Java enterprise backend | Spring Boot |
| 매 reactive, high-concurrency I/O | WebFlux + R2DBC |
| 매 traditional blocking I/O + Java 21 | Spring MVC + virtual threads |
| Native binary (cold start, low memory) | Spring Boot AOT + GraalVM |
| Lightweight Java (no DI ecosystem) | Quarkus / Micronaut / pure Javalin |

**기본값**: Spring Boot 3.4 + Java 21 + virtual threads + Spring MVC.

## 🔗 Graph
- 부모: [[Inversion of Control]]
- 변형: [[Spring Boot]]
- 응용: [[Microservices]]

## 🤖 LLM 활용
**언제**: Java backend, 매 enterprise integration (JPA, security, messaging) 필요.
**언제 X**: 매 ultra-low memory (serverless cold start) — Quarkus native 의 superior; 매 non-Java stack.

## ❌ 안티패턴
- **Field injection (`@Autowired` private field)**: 매 testability X, 매 final X. Constructor 의 사용.
- **God `@Configuration`**: 매 100+ bean 의 한 file — 매 module 별 분리.
- **`@Transactional` on private**: 매 proxy 의 work X. Public + self-injection 패턴.
- **Boot 1.x / Java 8**: 매 EOL, 매 vulnerable, 매 upgrade.

## 🧪 검증 / 중복
- Verified (spring.io docs, Spring Boot 3.4 release notes 2025).
- 신뢰도 A.

## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — Spring Boot 3.4 / Java 21 modern patterns |