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samples: add samples for object contexts (#3329)
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‎samples/snippets/src/main/java/com/example/storage/object/GetObjectContexts.java‎

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/*
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* Copyright 2025 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.storage.object;
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// [START storage_get_object_contexts]
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import com.google.cloud.storage.Blob;
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import com.google.cloud.storage.BlobInfo.ObjectContexts;
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import com.google.cloud.storage.BlobInfo.ObjectCustomContextPayload;
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import com.google.cloud.storage.Storage;
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import com.google.cloud.storage.StorageOptions;
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import java.util.Map;
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public class GetObjectContexts {
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public static void getObjectContexts(String projectId, String bucketName, String objectName)
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throws Exception {
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// The ID of your GCP project
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// String projectId = "your-project-id";
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// The ID of your GCS bucket
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// String bucketName = "your-unique-bucket-name";
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// The ID of your GCS object
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// String objectName = "your-object-name";
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try (Storage storage =
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StorageOptions.newBuilder().setProjectId(projectId).build().getService()) {
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Blob blob = storage.get(bucketName, objectName);
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if (blob == null) {
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System.out.println("The object " + objectName + " was not found in " + bucketName);
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return;
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}
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ObjectContexts objectContexts = blob.getContexts();
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if (objectContexts != null) {
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Map<String, ObjectCustomContextPayload> customContexts = objectContexts.getCustom();
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if (customContexts == null) {
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System.out.println("No custom contexts found for object: " + objectName);
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return;
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}
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// Print blob's object contexts
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System.out.println("\nCustom Contexts:");
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for (Map.Entry<String, ObjectCustomContextPayload> custom : customContexts.entrySet()) {
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System.out.println(custom.getKey() + "=" + custom.getValue());
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}
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}
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}
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}
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}
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// [END storage_get_object_contexts]

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

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/*
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* Copyright 2025 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.storage.object;
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// [START storage_list_object_contexts]
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import com.google.api.gax.paging.Page;
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import com.google.cloud.storage.Blob;
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import com.google.cloud.storage.Storage;
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import com.google.cloud.storage.StorageOptions;
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public class ListObjectContexts {
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public static void listObjectContexts(String projectId, String bucketName, String key)
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throws Exception {
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// The ID of your GCP project
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// String projectId = "your-project-id";
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// The ID of your GCS bucket
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// String bucketName = "your-unique-bucket-name";
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// The context key you want to filter
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// String key = "your-context-key";
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try (Storage storage =
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StorageOptions.newBuilder().setProjectId(projectId).build().getService()) {
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/*
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* List any object that has a context with the specified key attached
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* String filter = "contexts.\"KEY\":*";
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*
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* List any object that that does not have a context with the specified key attached
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* String filter = "NOT contexts.\"KEY\":*";
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*
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* List any object that has a context with the specified key and value attached
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* String filter = "contexts.\"KEY\"=\"VALUE\"";
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*
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* List any object that does not have a context with the specified key and value attached
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* String filter = "NOT contexts.\"KEY\"=\"VALUE\"";
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*/
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String filter = "contexts.\"" + key + "\":*";
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System.out.println("Listing objects for bucket: " + bucketName + "with context key: " + key);
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Page<Blob> blobs = storage.list(bucketName, Storage.BlobListOption.filter(filter));
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for (Blob blob : blobs.iterateAll()) {
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System.out.println(blob.getBlobId().toGsUtilUri());
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}
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}
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}
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}
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// [END storage_list_object_contexts]

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

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/*
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* Copyright 2025 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.example.storage.object;
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// [START storage_set_object_contexts]
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import com.google.cloud.storage.Blob;
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import com.google.cloud.storage.BlobId;
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import com.google.cloud.storage.BlobInfo;
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import com.google.cloud.storage.BlobInfo.ObjectContexts;
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import com.google.cloud.storage.BlobInfo.ObjectCustomContextPayload;
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import com.google.cloud.storage.Storage;
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import com.google.cloud.storage.StorageOptions;
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import com.google.common.collect.Maps;
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import java.util.Map;
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public class SetObjectContexts {
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public static void setObjectContexts(
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String projectId, String bucketName, String objectName, String key, String value)
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throws Exception {
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// The ID of your GCP project
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// String projectId = "your-project-id";
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// The ID of your GCS bucket
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// String bucketName = "your-unique-bucket-name";
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// The ID of your GCS object
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// String objectName = "your-object-name";
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// The context key-value you want to add
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// String key = "your-context-key";
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// String value = "your-context-value";
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try (Storage storage =
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StorageOptions.newBuilder().setProjectId(projectId).build().getService()) {
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BlobId blobId = BlobId.of(bucketName, objectName);
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Blob blob = storage.get(blobId);
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if (blob == null) {
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System.out.println("The object " + objectName + " was not found in " + bucketName);
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return;
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}
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// Recommended: Set a generation-match precondition to avoid potential race
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// conditions and data corruptions. The request to update returns a 412 error if
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// the object's generation number does not match your precondition.
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Storage.BlobTargetOption precondition = Storage.BlobTargetOption.generationMatch();
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// This section demonstrates how to upsert, delete all, and delete a specific context.
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// To upsert a context (if the key already exists, its value is replaced;
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// otherwise, a new key-value pair is added):
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ObjectCustomContextPayload payload =
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ObjectCustomContextPayload.newBuilder().setValue(value).build();
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Map<String, ObjectCustomContextPayload> custom = Maps.newHashMap();
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custom.put(key, payload);
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ObjectContexts contexts = ObjectContexts.newBuilder().setCustom(custom).build();
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/*
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* To delete all existing contexts:
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* ObjectContexts contexts = ObjectContexts.newBuilder().setCustom(null).build();
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*/
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/*
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* To delete a specific key from the context:
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* Map<String, ObjectCustomContextPayload> custom = Maps.newHashMap();
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* custom.put(key, null);
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* ObjectContexts contexts = ObjectContexts.newBuilder().setCustom(custom).build();
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*/
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BlobInfo pendingUpdate = blob.toBuilder().setContexts(contexts).build();
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storage.update(pendingUpdate, precondition);
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System.out.println(
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"Updated custom contexts for object " + objectName + " in bucket " + bucketName);
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}
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}
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}
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// [END storage_set_object_contexts]

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