blobstore: change validate bucket exists method (#305)

Author: Yaminik1996

blob/blob-gcp/src/main/java/com/salesforce/multicloudj/blob/gcp/GcpBlobStore.java

@@ -50,7 +50,6 @@
 import com.salesforce.multicloudj.blob.driver.DownloadRequest;
 import com.salesforce.multicloudj.blob.driver.DownloadResponse;
 import com.salesforce.multicloudj.blob.driver.FailedBlobDownload;
-import com.salesforce.multicloudj.common.exceptions.UnSupportedOperationException;
 import com.salesforce.multicloudj.blob.driver.FailedBlobUpload;
 import com.salesforce.multicloudj.blob.driver.ListBlobsPageRequest;
 import com.salesforce.multicloudj.blob.driver.ListBlobsPageResponse;
@@ -261,7 +260,6 @@ protected void doDelete(Collection<BlobIdentifier> objects) {
         List<BlobId> blobIds = objects.stream()
                 .map(obj -> transformer.toBlobId(bucket, obj.getKey(), obj.getVersionId()))
                 .collect(Collectors.toList());
-        
         storage.delete(blobIds);
     }
 
@@ -453,17 +451,19 @@ protected void doAbortMultipartUpload(MultipartUpload mpu) {
 
     /**
      * Validates that the bucket exists, throwing ResourceNotFoundException if not found.
+     * Uses Objects.List with pageSize(1) instead of Buckets.Get so that only
+     * {@code storage.objects.list} is required on the bucket, not {@code storage.buckets.get}.
      *
      * @throws ResourceNotFoundException if the bucket does not exist
      */
     private void validateBucketExists() {
         try {
-            Bucket bucketObj = storage.get(bucket);
-            if (bucketObj == null) {
-                throw new ResourceNotFoundException("Bucket not found: " + bucket);
-            }
+            storage.list(getBucket(), Storage.BlobListOption.pageSize(1));
         } catch (StorageException e) {
-            throw new ResourceNotFoundException("Bucket not found: " + bucket, e);
+            if (e.getCode() == 404) {
+                throw new ResourceNotFoundException("Bucket not found: " + bucket, e);
+            }
+            throw new UnknownException("Failed to check bucket existence", e);
         }
     }
 

blob/blob-gcp/src/test/java/com/salesforce/multicloudj/blob/gcp/GcpBlobStoreTest.java

@@ -108,6 +108,7 @@
 import static org.mockito.ArgumentMatchers.anyInt;
 import static org.mockito.ArgumentMatchers.anyLong;
 import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.anyString;
 import static org.mockito.Mockito.doReturn;
 import static org.mockito.Mockito.doThrow;
 import static org.mockito.Mockito.lenient;
@@ -603,6 +604,7 @@ void testDoDownload_WithPath_ThrowsException() {
     void testDoDelete_WithKeyAndVersionId() {
         // Given
         when(mockTransformer.toBlobId(TEST_BUCKET, TEST_KEY, TEST_VERSION_ID)).thenReturn(mockBlobId);
+        when(mockStorage.list(anyString(), any())).thenReturn(null);
 
         // When
         gcpBlobStore.doDelete(TEST_KEY, TEST_VERSION_ID);