feat(storage): add object existence validation option to get presigne…

…d url

aws-storage-s3/src/main/java/com/amplifyframework/storage/s3/AWSS3StoragePlugin.java

@@ -355,10 +355,15 @@ public StorageGetUrlOperation<?> getUrl(
     ) {
         boolean useAccelerateEndpoint = options instanceof AWSS3StorageGetPresignedUrlOptions &&
                 ((AWSS3StorageGetPresignedUrlOptions) options).useAccelerateEndpoint();
+
+        boolean validateObjectExistence = options instanceof AWSS3StorageGetPresignedUrlOptions &&
+                ((AWSS3StorageGetPresignedUrlOptions) options).validateObjectExistence();
+
         AWSS3StoragePathGetPresignedUrlRequest request = new AWSS3StoragePathGetPresignedUrlRequest(
                 path,
                 options.getExpires() != 0 ? options.getExpires() : defaultUrlExpiration,
-                useAccelerateEndpoint
+                useAccelerateEndpoint,
+                validateObjectExistence
         );
 
         AWSS3StoragePathGetPresignedUrlOperation operation =

aws-storage-s3/src/main/java/com/amplifyframework/storage/s3/operation/AWSS3StoragePathGetPresignedUrlOperation.kt

@@ -48,6 +48,24 @@ internal class AWSS3StoragePathGetPresignedUrlOperation(
                 return@submit
             }
 
+            if (request.validateObjectExistence) {
+                try {
+                    storageService.validateObjectExists(serviceKey)
+                } catch (se: StorageException) {
+                    onError.accept(se)
+                    return@submit
+                } catch (exception: Exception) {
+                    onError.accept(
+                        StorageException(
+                            "Encountered an issue while generating pre-signed URL",
+                            exception,
+                            "See included exception for more details and suggestions to fix."
+                        )
+                    )
+                    return@submit
+                }
+            }
+
             try {
                 val url = storageService.getPresignedUrl(
                     serviceKey,

aws-storage-s3/src/main/java/com/amplifyframework/storage/s3/options/AWSS3StorageGetPresignedUrlOptions.java

@@ -26,10 +26,12 @@
  */
 public final class AWSS3StorageGetPresignedUrlOptions extends StorageGetUrlOptions {
     private final boolean useAccelerationMode;
+    private final boolean validateObjectExistence;
 
     private AWSS3StorageGetPresignedUrlOptions(final Builder builder) {
         super(builder);
         this.useAccelerationMode = builder.useAccelerateEndpoint;
+        this.validateObjectExistence = builder.validateObjectExistence;
     }
 
     /**
@@ -80,6 +82,16 @@ public boolean useAccelerateEndpoint() {
         return useAccelerationMode;
     }
 
+    /**
+     * Gets the flag to determine whether to validate whether an S3 object exists.
+     * Note: Setting this to `true` will result in a latency cost since confirming the existence
+     * of the underlying S3 object will likely require a round-trip network call.
+     * @return boolean flag
+     */
+    public boolean validateObjectExistence() {
+        return validateObjectExistence;
+    }
+
     @Override
     @SuppressWarnings("deprecation")
     public boolean equals(Object obj) {
@@ -123,6 +135,7 @@ public String toString() {
      */
     public static final class Builder extends StorageGetUrlOptions.Builder<Builder> {
         private boolean useAccelerateEndpoint;
+        private boolean validateObjectExistence;
 
         /**
          * Configure to use acceleration mode on new StorageGetPresignedUrlOptions instances.
@@ -134,6 +147,16 @@ public Builder setUseAccelerateEndpoint(boolean useAccelerateEndpoint) {
             return this;
         }
 
+        /**
+         * Configure to validate object existence flag on new StorageGetPresignedUrlOptions instances.
+         * @param validateObjectExistence flag to represent flag to validate object existence for new GetPresignedUrlOptions instance
+         * @return Current Builder instance for fluent chaining
+         */
+        public Builder setValidateObjectExistence(boolean validateObjectExistence) {
+            this.validateObjectExistence = validateObjectExistence;
+            return this;
+        }
+
         @Override
         @NonNull
         public AWSS3StorageGetPresignedUrlOptions build() {

aws-storage-s3/src/main/java/com/amplifyframework/storage/s3/request/AWSS3StoragePathGetPresignedUrlRequest.kt

@@ -22,5 +22,6 @@ import com.amplifyframework.storage.StoragePath
 internal data class AWSS3StoragePathGetPresignedUrlRequest(
     val path: StoragePath,
     val expires: Int,
-    val useAccelerateEndpoint: Boolean
+    val useAccelerateEndpoint: Boolean,
+    val validateObjectExistence: Boolean
 )

aws-storage-s3/src/main/java/com/amplifyframework/storage/s3/service/AWSS3StorageService.kt

@@ -20,18 +20,22 @@ import aws.sdk.kotlin.services.s3.S3Client
 import aws.sdk.kotlin.services.s3.deleteObject
 import aws.sdk.kotlin.services.s3.listObjectsV2
 import aws.sdk.kotlin.services.s3.model.GetObjectRequest
+import aws.sdk.kotlin.services.s3.model.HeadObjectRequest
+import aws.sdk.kotlin.services.s3.model.NotFound
 import aws.sdk.kotlin.services.s3.paginators.listObjectsV2Paginated
 import aws.sdk.kotlin.services.s3.presigners.presignGetObject
 import aws.sdk.kotlin.services.s3.withConfig
 import com.amplifyframework.auth.AuthCredentialsProvider
 import com.amplifyframework.storage.ObjectMetadata
+import com.amplifyframework.storage.StorageException
 import com.amplifyframework.storage.StorageItem
 import com.amplifyframework.storage.result.StorageListResult
 import com.amplifyframework.storage.s3.transfer.TransferManager
 import com.amplifyframework.storage.s3.transfer.TransferObserver
 import com.amplifyframework.storage.s3.transfer.TransferRecord
 import com.amplifyframework.storage.s3.transfer.UploadOptions
 import com.amplifyframework.storage.s3.utils.S3Keys
+import kotlinx.coroutines.runBlocking
 import java.io.File
 import java.io.IOException
 import java.io.InputStream
@@ -40,7 +44,6 @@ import java.time.Instant
 import java.util.Date
 import kotlin.time.Duration.Companion.seconds
 import kotlin.time.ExperimentalTime
-import kotlinx.coroutines.runBlocking
 
 /**
  * A representation of an S3 backend service endpoint.
@@ -85,6 +88,30 @@ internal class AWSS3StorageService(
         return URL(presignUrlRequest.url.toString())
     }
 
+    /**
+     * Validate if S3 object exists for the given key.
+     * Throws StorageException if NoSuchKey S3 client exception is caught.
+     * @param serviceKey S3 service key
+     */
+    override fun validateObjectExists(serviceKey: String) {
+        try {
+            runBlocking {
+                s3Client.headObject(
+                    HeadObjectRequest {
+                        bucket = s3BucketName
+                        key = serviceKey
+                    }
+                )
+            }
+        } catch (ex: NotFound) {
+            throw StorageException(
+                "Unable to generate URL for non-existent path: $serviceKey",
+                ex,
+                "Please ensure the path is valid or the object has been uploaded"
+            )
+        }
+    }
+
     /**
      * Begin downloading a file.
      * @param serviceKey S3 service key

aws-storage-s3/src/main/java/com/amplifyframework/storage/s3/service/StorageService.java

@@ -20,6 +20,7 @@
 import androidx.annotation.Nullable;
 
 import com.amplifyframework.storage.ObjectMetadata;
+import com.amplifyframework.storage.StorageException;
 import com.amplifyframework.storage.StorageItem;
 import com.amplifyframework.storage.result.StorageListResult;
 import com.amplifyframework.storage.s3.transfer.TransferObserver;
@@ -36,6 +37,14 @@
  */
 public interface StorageService {
 
+    /**
+     * Validate if Storage object exists for the given key.
+     * Throws StorageException if object is not does not exist.
+     *
+     * @param serviceKey key to uniquely specify item to generate URL for
+     */
+    void validateObjectExists(@NonNull String serviceKey);
+
     /**
      * Generate pre-signed download URL for an object.
      *

aws-storage-s3/src/test/java/com/amplifyframework/storage/s3/operation/AWSS3StoragePathGetUrlOperationTest.kt

@@ -33,7 +33,7 @@ import org.junit.Test
 
 class AWSS3StoragePathGetUrlOperationTest {
 
-    private lateinit var awsS3StorageDownloadFileOperation: AWSS3StoragePathGetPresignedUrlOperation
+    private lateinit var awsS3StorageGetPresignedUrlOperation: AWSS3StoragePathGetPresignedUrlOperation
     private lateinit var storageService: StorageService
     private lateinit var authCredentialsProvider: AuthCredentialsProvider
 
@@ -53,10 +53,11 @@ class AWSS3StoragePathGetUrlOperationTest {
         val request = AWSS3StoragePathGetPresignedUrlRequest(
             path,
             expectedExpires,
-            false
+            false,
+            validateObjectExistence = false
         )
         val onError = mockk<Consumer<StorageException>>(relaxed = true)
-        awsS3StorageDownloadFileOperation = AWSS3StoragePathGetPresignedUrlOperation(
+        awsS3StorageGetPresignedUrlOperation = AWSS3StoragePathGetPresignedUrlOperation(
             request = request,
             storageService = storageService,
             executorService = MoreExecutors.newDirectExecutorService(),
@@ -66,7 +67,7 @@ class AWSS3StoragePathGetUrlOperationTest {
         )
 
         // WHEN
-        awsS3StorageDownloadFileOperation.start()
+        awsS3StorageGetPresignedUrlOperation.start()
 
         // THEN
         verify(exactly = 0) { onError.accept(any()) }
@@ -88,10 +89,11 @@ class AWSS3StoragePathGetUrlOperationTest {
         val request = AWSS3StoragePathGetPresignedUrlRequest(
             path,
             expectedExpires,
-            false
+            false,
+            validateObjectExistence = false
         )
         val onError = mockk<Consumer<StorageException>>(relaxed = true)
-        awsS3StorageDownloadFileOperation = AWSS3StoragePathGetPresignedUrlOperation(
+        awsS3StorageGetPresignedUrlOperation = AWSS3StoragePathGetPresignedUrlOperation(
             request = request,
             storageService = storageService,
             executorService = MoreExecutors.newDirectExecutorService(),
@@ -101,7 +103,7 @@ class AWSS3StoragePathGetUrlOperationTest {
         )
 
         // WHEN
-        awsS3StorageDownloadFileOperation.start()
+        awsS3StorageGetPresignedUrlOperation.start()
 
         // THEN
         verify(exactly = 0) { onError.accept(any()) }
@@ -122,10 +124,11 @@ class AWSS3StoragePathGetUrlOperationTest {
         val request = AWSS3StoragePathGetPresignedUrlRequest(
             path,
             expectedExpires,
-            false
+            false,
+            validateObjectExistence = false
         )
         val onError = mockk<Consumer<StorageException>>(relaxed = true)
-        awsS3StorageDownloadFileOperation = AWSS3StoragePathGetPresignedUrlOperation(
+        awsS3StorageGetPresignedUrlOperation = AWSS3StoragePathGetPresignedUrlOperation(
             request = request,
             storageService = storageService,
             executorService = MoreExecutors.newDirectExecutorService(),
@@ -135,7 +138,7 @@ class AWSS3StoragePathGetUrlOperationTest {
         )
 
         // WHEN
-        awsS3StorageDownloadFileOperation.start()
+        awsS3StorageGetPresignedUrlOperation.start()
 
         // THEN
         verify { onError.accept(StoragePathValidationException.invalidStoragePathException()) }
@@ -153,10 +156,11 @@ class AWSS3StoragePathGetUrlOperationTest {
         val request = AWSS3StoragePathGetPresignedUrlRequest(
             path,
             expectedExpires,
-            false
+            false,
+            validateObjectExistence = false
         )
         val onError = mockk<Consumer<StorageException>>(relaxed = true)
-        awsS3StorageDownloadFileOperation = AWSS3StoragePathGetPresignedUrlOperation(
+        awsS3StorageGetPresignedUrlOperation = AWSS3StoragePathGetPresignedUrlOperation(
             request = request,
             storageService = storageService,
             executorService = MoreExecutors.newDirectExecutorService(),
@@ -166,7 +170,7 @@ class AWSS3StoragePathGetUrlOperationTest {
         )
 
         // WHEN
-        awsS3StorageDownloadFileOperation.start()
+        awsS3StorageGetPresignedUrlOperation.start()
 
         // THEN
         verify {
@@ -190,10 +194,11 @@ class AWSS3StoragePathGetUrlOperationTest {
         val request = AWSS3StoragePathGetPresignedUrlRequest(
             path,
             expectedExpires,
-            false
+            false,
+            validateObjectExistence = false
         )
         val onError = mockk<Consumer<StorageException>>(relaxed = true)
-        awsS3StorageDownloadFileOperation = AWSS3StoragePathGetPresignedUrlOperation(
+        awsS3StorageGetPresignedUrlOperation = AWSS3StoragePathGetPresignedUrlOperation(
             request = request,
             storageService = storageService,
             executorService = MoreExecutors.newDirectExecutorService(),
@@ -203,7 +208,7 @@ class AWSS3StoragePathGetUrlOperationTest {
         )
 
         // WHEN
-        awsS3StorageDownloadFileOperation.start()
+        awsS3StorageGetPresignedUrlOperation.start()
 
         // THEN
         verify { onError.accept(StoragePathValidationException.unsupportedStoragePathException()) }
@@ -212,5 +217,72 @@ class AWSS3StoragePathGetUrlOperationTest {
         }
     }
 
+    @Test
+    fun `getPresignedUrl fails with non existent S3 path when validateObjectExistence is enabled`() {
+        // GIVEN
+        val path = StoragePath.fromString("public/123")
+        val expectedException = StorageException("Test", "Test")
+        coEvery { storageService.validateObjectExists(any()) } throws expectedException
+        val request = AWSS3StoragePathGetPresignedUrlRequest(
+            path,
+            expectedExpires,
+            false,
+            validateObjectExistence = true
+        )
+        val onError = mockk<Consumer<StorageException>>(relaxed = true)
+        awsS3StorageGetPresignedUrlOperation = AWSS3StoragePathGetPresignedUrlOperation(
+            request = request,
+            storageService = storageService,
+            executorService = MoreExecutors.newDirectExecutorService(),
+            authCredentialsProvider = authCredentialsProvider,
+            onSuccess = {},
+            onError = onError
+        )
+
+        // WHEN
+        awsS3StorageGetPresignedUrlOperation.start()
+
+        // THEN
+        verify(exactly = 1) { onError.accept(expectedException) }
+        verify(exactly = 0) {
+            storageService.getPresignedUrl(any(), any(), any())
+        }
+    }
+
+    @Test
+    fun `getPresignedUrl succeeds when validateObjectExistence is enabled`() {
+        // GIVEN
+        val path = StoragePath.fromString("public/123")
+        val expectedServiceKey = "public/123"
+        val request = AWSS3StoragePathGetPresignedUrlRequest(
+            path,
+            expectedExpires,
+            false,
+            validateObjectExistence = true
+        )
+        val onError = mockk<Consumer<StorageException>>(relaxed = true)
+        awsS3StorageGetPresignedUrlOperation = AWSS3StoragePathGetPresignedUrlOperation(
+            request = request,
+            storageService = storageService,
+            executorService = MoreExecutors.newDirectExecutorService(),
+            authCredentialsProvider = authCredentialsProvider,
+            onSuccess = {},
+            onError = onError
+        )
+
+        // WHEN
+        awsS3StorageGetPresignedUrlOperation.start()
+
+        // THEN
+        verify(exactly = 0) { onError.accept(any()) }
+        verify {
+            storageService.getPresignedUrl(
+                expectedServiceKey,
+                expectedExpires,
+                false
+            )
+        }
+    }
+
     class UnsupportedStoragePath : StoragePath()
 }