docs: add batch sample

README.md

@@ -294,6 +294,7 @@ Samples are in the [`samples/`](https://github.com/googleapis/java-storage/tree/
 | Get Hmac Key | [source code](https://github.com/googleapis/java-storage/blob/main/samples/snippets/src/main/java/com/example/storage/hmac/GetHmacKey.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-storage&page=editor&open_in_editor=samples/snippets/src/main/java/com/example/storage/hmac/GetHmacKey.java) |
 | List Hmac Keys | [source code](https://github.com/googleapis/java-storage/blob/main/samples/snippets/src/main/java/com/example/storage/hmac/ListHmacKeys.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-storage&page=editor&open_in_editor=samples/snippets/src/main/java/com/example/storage/hmac/ListHmacKeys.java) |
 | Add File Owner | [source code](https://github.com/googleapis/java-storage/blob/main/samples/snippets/src/main/java/com/example/storage/object/AddFileOwner.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-storage&page=editor&open_in_editor=samples/snippets/src/main/java/com/example/storage/object/AddFileOwner.java) |
+| Batch Set Object Metadata | [source code](https://github.com/googleapis/java-storage/blob/main/samples/snippets/src/main/java/com/example/storage/object/BatchSetObjectMetadata.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-storage&page=editor&open_in_editor=samples/snippets/src/main/java/com/example/storage/object/BatchSetObjectMetadata.java) |
 | Change Object Csek To Kms | [source code](https://github.com/googleapis/java-storage/blob/main/samples/snippets/src/main/java/com/example/storage/object/ChangeObjectCsekToKms.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-storage&page=editor&open_in_editor=samples/snippets/src/main/java/com/example/storage/object/ChangeObjectCsekToKms.java) |
 | Change Object Storage Class | [source code](https://github.com/googleapis/java-storage/blob/main/samples/snippets/src/main/java/com/example/storage/object/ChangeObjectStorageClass.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-storage&page=editor&open_in_editor=samples/snippets/src/main/java/com/example/storage/object/ChangeObjectStorageClass.java) |
 | Compose Object | [source code](https://github.com/googleapis/java-storage/blob/main/samples/snippets/src/main/java/com/example/storage/object/ComposeObject.java) | [![Open in Cloud Shell][shell_img]](https://console.cloud.google.com/cloudshell/open?git_repo=https://github.com/googleapis/java-storage&page=editor&open_in_editor=samples/snippets/src/main/java/com/example/storage/object/ComposeObject.java) |

samples/snippets/src/main/java/com/example/storage/object/BatchSetObjectMetadata.java

@@ -0,0 +1,67 @@
+/*
+ * Copyright 2022 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.example.storage.object;
+
+// [START storage_batch_request]
+import com.google.api.gax.paging.Page;
+import com.google.cloud.storage.Blob;
+import com.google.cloud.storage.Storage;
+import com.google.cloud.storage.StorageBatch;
+import com.google.cloud.storage.StorageOptions;
+import java.util.HashMap;
+import java.util.Map;
+
+public class BatchSetObjectMetadata {
+  public static void batchSetObjectMetadata(
+      String projectId, String bucketName, String directoryPrefix) {
+    // The ID of your GCP project
+    // String projectId = "your-project-id";
+
+    // The ID of your GCS bucket
+    // String bucketName = "your-unique-bucket-name";
+
+    // The directory prefix. All objects in the bucket with this prefix will have their metadata
+    // updated
+    // String directoryPrefix = "yourDirectory/";
+
+    Storage storage = StorageOptions.newBuilder().setProjectId(projectId).build().getService();
+    Map<String, String> newMetadata = new HashMap<>();
+    newMetadata.put("keyToAddOrUpdate", "value");
+    Page<Blob> blobs =
+        storage.list(
+            bucketName,
+            Storage.BlobListOption.prefix(directoryPrefix),
+            Storage.BlobListOption.currentDirectory());
+    StorageBatch batchRequest = storage.batch();
+
+    // Add all blobs with the given prefix to the batch request
+    for (Blob blob : blobs.iterateAll()) {
+      batchRequest.update(blob.toBuilder().setMetadata(newMetadata).build());
+    }
+
+    // Execute the batch request
+    batchRequest.submit();
+
+    System.out.println(
+        "All blobs in bucket "
+            + bucketName
+            + " with prefix '"
+            + directoryPrefix
+            + "' had their metadata updated.");
+  }
+}
+// [END storage_batch_request]

samples/snippets/src/test/java/com/example/storage/ITObjectSnippets.java

@@ -24,6 +24,7 @@
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
+import com.example.storage.object.BatchSetObjectMetadata;
 import com.example.storage.object.ChangeObjectCsekToKms;
 import com.example.storage.object.ChangeObjectStorageClass;
 import com.example.storage.object.ComposeObject;
@@ -416,4 +417,18 @@ public void testUploadKMSEncryptedObject() {
     UploadKmsEncryptedObject.uploadKmsEncryptedObject(PROJECT_ID, BUCKET, blobName, KMS_KEY_NAME);
     assertNotNull(storage.get(BUCKET, blobName));
   }
+
+  @Test
+  public void testBatchSetObjectMetadata() {
+    storage.create(BlobInfo.newBuilder(BUCKET, "b/1.txt").build());
+    storage.create(BlobInfo.newBuilder(BUCKET, "b/2.txt").build());
+
+    BatchSetObjectMetadata.batchSetObjectMetadata(PROJECT_ID, BUCKET, "b/");
+
+    Map<String, String> firstBlobMetadata = storage.get(BUCKET, "b/1.txt").getMetadata();
+    Map<String, String> secondBlobMetadata = storage.get(BUCKET, "b/2.txt").getMetadata();
+
+    assertEquals("value", firstBlobMetadata.get("keyToAddOrUpdate"));
+    assertEquals("value", secondBlobMetadata.get("keyToAddOrUpdate"));
+  }
 }