Amazon S3

// application.yml — 키 설정 없음
cloud:
  aws:
    region:
      static: ap-northeast-2
    # EC2에 IAM 역할이 붙어 있으면 자격증명 자동 주입

// S3Service.java
@Service
public class S3Service {
    private final AmazonS3 s3;  // IAM 역할로 자동 인증

    public String upload(MultipartFile file) {
        String key = "uploads/" + UUID.randomUUID() + "_" + file.getOriginalFilename();
        s3.putObject(bucketName, key, file.getInputStream(), metadata);
        return key;
    }
}

// 프리사인드 URL 생성 (15분 유효)
public String getPresignedUrl(String key) {
    Date expiration = new Date(System.currentTimeMillis() + 15 * 60 * 1000);
    GeneratePresignedUrlRequest request =
        new GeneratePresignedUrlRequest(bucketName, key)
            .withExpiration(expiration);
    return s3.generatePresignedUrl(request).toString();
}

// 생성된 URL 예시
https://my-bucket.s3.ap-northeast-2.amazonaws.com/uploads/photo.jpg
  ?X-Amz-Algorithm=AWS4-HMAC-SHA256
  &X-Amz-Expires=900
  &X-Amz-Signature=abc123...