#9 feat : S3 파일 관리 메소드 작성

- 이미지 업로드 - 이미지 공개 url을 반환
- 파일 업로드
- 파일 다운로드
- MultiPart -> File 변환 메소드

src/main/java/gdsc/comunity/service/S3FileService.java

@@ -0,0 +1,69 @@
+package gdsc.comunity.service;
+
+import com.amazonaws.services.s3.AmazonS3;
+import com.amazonaws.services.s3.AmazonS3ClientBuilder;
+import com.amazonaws.services.s3.model.CannedAccessControlList;
+import com.amazonaws.services.s3.model.GetObjectRequest;
+import com.amazonaws.services.s3.model.PutObjectRequest;
+import gdsc.comunity.exception.CustomException;
+import gdsc.comunity.exception.ErrorCode;
+import java.io.File;
+import java.util.UUID;
+import org.springframework.stereotype.Component;
+import org.springframework.web.multipart.MultipartFile;
+
+@Component
+public class S3FileService {
+    private final AmazonS3 s3Client;
+
+    private final String bucketName = "mohaji";
+
+    public S3FileService() {
+        this.s3Client = AmazonS3ClientBuilder.defaultClient();
+    }
+
+    public String uploadImage(MultipartFile image){
+        String s3FileName = UUID.randomUUID().toString().substring(0, 10) + "_" + image.getOriginalFilename();
+        try {
+            File convertedFile = convertMultiPartFileToFile(image);
+            s3Client.putObject(new PutObjectRequest(bucketName, s3FileName, convertedFile)
+                .withCannedAcl(CannedAccessControlList.PublicRead));
+        } catch (Exception e) {
+            throw new CustomException(ErrorCode.FILE_UPLOAD_ERROR);
+        }
+
+        return s3Client.getUrl(bucketName, s3FileName).toString();
+    }
+
+    public String uploadFile(MultipartFile file) {
+        String s3FileName = UUID.randomUUID().toString().substring(0, 10) + "_" + file.getOriginalFilename();
+        try {
+            File convertedFile = convertMultiPartFileToFile(file);
+            s3Client.putObject(new PutObjectRequest(bucketName, s3FileName, convertedFile));
+        } catch (Exception e) {
+            throw new CustomException(ErrorCode.FILE_UPLOAD_ERROR);
+        }
+        return s3FileName;
+    }
+
+    public File downloadFile(String s3FileName) {
+        try {
+            File file = File.createTempFile(s3FileName.substring(11), null);
+            s3Client.getObject(new GetObjectRequest(bucketName, s3FileName), file);
+            return file;
+        } catch (Exception e) {
+            throw new CustomException(ErrorCode.FILE_DOWNLOAD_ERROR);
+        }
+    }
+
+    private File convertMultiPartFileToFile(MultipartFile file) {
+        File convertedFile = new File(file.getOriginalFilename());
+        try {
+            file.transferTo(convertedFile);
+        } catch (Exception e) {
+            throw new CustomException(ErrorCode.FILE_TRANSFORM_ERROR);
+        }
+        return convertedFile;
+    }
+
+}