[Spring] ResponseEntity의 유용한 메소드들 [200 OK, 400 Bad Request, 404 Not Found, 201 Created 등]

---

- ResponseEntity의 유용한 메소드들

1. ResponseEntity.ok(): 200 OK 응답 반환

return ResponseEntity.ok("성공");

---

2. ResponseEntity.badRequest(): 400 Bad Request 응답 반환

return ResponseEntity.badRequest().body("잘못된 요청입니다.");

---

3. ResponseEntity.notFound(): 404 Not Found 응답 반환

return ResponseEntity.notFound().build();

---

4. ResponseEntity.created(): 201 Created 응답 반환 (새로운 리소스 생성 시)

URI location = URI.create("/resource/1");
return ResponseEntity.created(location).build();

---

5. ResponseEntity.status(HttpStatus): 다른 HTTP 상태 코드 반환

return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("서버 오류 발생");

---

6. ResponseEntity.headers(): 헤더를 설정할 수 있음

HttpHeaders headers = new HttpHeaders();
headers.add("Custom-Header", "Header-Value");
return ResponseEntity.ok().headers(headers).body("헤더 포함된 응답");

---