组合对象

概览

本页面介绍如何将 Cloud Storage 对象组合为单个对象。组合请求可接受 1 到 32 个对象，并创建一个新的复合对象。复合对象按照请求中指定的顺序将各源对象连接起来。

在组合对象时，请注意以下事项：

  • 源对象不受组合过程的影响。如果您希望它们暂时存在，则顺利完成组合后您必须删除它们。

所需的角色

如需获得组合对象所需的权限，请让您的管理员为您授予存储桶的 Storage Object User (roles/storage.objectUser) IAM 角色。此预定义角色包含组合对象所需的权限。如需查看所需的确切权限，请展开所需权限部分：

所需权限

  • storage.objects.create
  • storage.objects.delete
    • 仅当您想要为您组合的对象指定与存储桶中已存在的对象相同的名称时，才需要此权限。
  • storage.objects.get
  • storage.objects.list
    • 仅当您想要使用通配符以相同前缀组合对象而无需在 Google Cloud CLI 命令中单独列出每个对象时，才需要此权限。

如果您想要为所组合的对象设置保留配置，则还需要 storage.objects.setRetention 权限。如需获得此权限，请让您的管理员为您授予 Storage Object Admin (roles/storage.objectAdmin) 角色，而不是 Storage Object User (roles/storage.objectUser) 角色。

您也可以使用其他预定义角色或自定义角色来获得这些权限。

如需了解如何授予存储桶的角色，请参阅将 IAM 与存储桶搭配使用。

创建复合对象

命令行

使用 gcloud storage objects compose 命令：

gcloud storage objects compose gs://BUCKET_NAME/SOURCE_OBJECT_1 gs://BUCKET_NAME/SOURCE_OBJECT_2 gs://BUCKET_NAME/COMPOSITE_OBJECT_NAME

其中：

  • BUCKET_NAME 是包含源对象的存储桶的名称。
  • SOURCE_OBJECT_1 和 SOURCE_OBJECT_2 是对象组合过程中使用的源对象的名称。
  • COMPOSITE_OBJECT_NAME 是您赋予对象组合成果的名称。

客户端库

C++

如需了解详情，请参阅 Cloud Storage C++ API 参考文档。

如需向 Cloud Storage 进行身份验证，请设置应用默认凭据。 如需了解详情，请参阅为客户端库设置身份验证。 

namespace gcs = ::google::cloud::storage;
using ::google::cloud::StatusOr;
[](gcs::Client client, std::string const& bucket_name,
   std::string const& destination_object_name,
   std::vector<gcs::ComposeSourceObject> const& compose_objects) {
  StatusOr<gcs::ObjectMetadata> composed_object = client.ComposeObject(
      bucket_name, compose_objects, destination_object_name);
  if (!composed_object) throw std::move(composed_object).status();

  std::cout << "Composed new object " << composed_object->name()
            << " in bucket " << composed_object->bucket()
            << "\nFull metadata: " << *composed_object << "\n";
}

C#

如需了解详情，请参阅 Cloud Storage C# API 参考文档。

如需向 Cloud Storage 进行身份验证，请设置应用默认凭据。 如需了解详情，请参阅为客户端库设置身份验证。 


using Google.Apis.Storage.v1.Data;
using Google.Cloud.Storage.V1;
using System;
using System.Collections.Generic;

public class ComposeObjectSample
{
    public void ComposeObject(
        string bucketName = "your-bucket-name",
        string firstObjectName = "your-first-object-name",
        string secondObjectName = "your-second-object-name",
        string targetObjectName = "new-composite-object-name")
    {
        var storage = StorageClient.Create();

        var sourceObjects = new List<ComposeRequest.SourceObjectsData>
        {
            new ComposeRequest.SourceObjectsData { Name = firstObjectName },
            new ComposeRequest.SourceObjectsData { Name = secondObjectName }
        };
        //You could add as many sourceObjects as you want here, up to the max of 32.

        storage.Service.Objects.Compose(new ComposeRequest
        {
            SourceObjects = sourceObjects,
            Destination = new Google.Apis.Storage.v1.Data.Object { ContentType = "text/plain" }
        }, bucketName, targetObjectName).Execute();

        Console.WriteLine($"New composite file {targetObjectName} was created in bucket {bucketName}" +
            $" by combining {firstObjectName} and {secondObjectName}.");
    }
}

Go

如需了解详情，请参阅 Cloud Storage Go API 参考文档。

如需向 Cloud Storage 进行身份验证，请设置应用默认凭据。 如需了解详情，请参阅为客户端库设置身份验证。 

import (
	"context"
	"fmt"
	"io"
	"time"

	"cloud.google.com/go/storage"
)

// composeFile composes source objects to create a composite object.
func composeFile(w io.Writer, bucket, object1, object2, toObject string) error {
	// bucket := "bucket-name"
	// object1 := "object-name-1"
	// object2 := "object-name-2"
	// toObject := "object-name-3"

	ctx := context.Background()
	client, err := storage.NewClient(ctx)
	if err != nil {
		return fmt.Errorf("storage.NewClient: %w", err)
	}
	defer client.Close()

	ctx, cancel := context.WithTimeout(ctx, time.Second*10)
	defer cancel()

	src1 := client.Bucket(bucket).Object(object1)
	src2 := client.Bucket(bucket).Object(object2)
	dst := client.Bucket(bucket).Object(toObject)

	// ComposerFrom takes varargs, so you can put as many objects here
	// as you want.
	_, err = dst.ComposerFrom(src1, src2).Run(ctx)
	if err != nil {
		return fmt.Errorf("ComposerFrom: %w", err)
	}
	fmt.Fprintf(w, "New composite object %v was created by combining %v and %v\n", toObject, object1, object2)
	return nil
}

Java

如需了解详情，请参阅 Cloud Storage Java API 参考文档。

如需向 Cloud Storage 进行身份验证，请设置应用默认凭据。 如需了解详情，请参阅为客户端库设置身份验证。 

import com.google.cloud.storage.Blob;
import com.google.cloud.storage.BlobInfo;
import com.google.cloud.storage.Storage;
import com.google.cloud.storage.StorageOptions;

public class ComposeObject {
  public static void composeObject(
      String bucketName,
      String firstObjectName,
      String secondObjectName,
      String targetObjectName,
      String projectId) {
    // The ID of your GCP project
    // String projectId = "your-project-id";

    // The ID of your GCS bucket
    // String bucketName = "your-unique-bucket-name";

    // The ID of the first GCS object to compose
    // String firstObjectName = "your-first-object-name";

    // The ID of the second GCS object to compose
    // String secondObjectName = "your-second-object-name";

    // The ID to give the new composite object
    // String targetObjectName = "new-composite-object-name";

    Storage storage = StorageOptions.newBuilder().setProjectId(projectId).build().getService();

    // Optional: set a generation-match precondition to avoid potential race
    // conditions and data corruptions. The request returns a 412 error if the
    // preconditions are not met.
    Storage.BlobTargetOption precondition;
    if (storage.get(bucketName, targetObjectName) == null) {
      // For a target object that does not yet exist, set the DoesNotExist precondition.
      // This will cause the request to fail if the object is created before the request runs.
      precondition = Storage.BlobTargetOption.doesNotExist();
    } else {
      // If the destination already exists in your bucket, instead set a generation-match
      // precondition. This will cause the request to fail if the existing object's generation
      // changes before the request runs.
      precondition =
          Storage.BlobTargetOption.generationMatch(
              storage.get(bucketName, targetObjectName).getGeneration());
    }

    Storage.ComposeRequest composeRequest =
        Storage.ComposeRequest.newBuilder()
            // addSource takes varargs, so you can put as many objects here as you want, up to the
            // max of 32
            .addSource(firstObjectName, secondObjectName)
            .setTarget(BlobInfo.newBuilder(bucketName, targetObjectName).build())
            .setTargetOptions(precondition)
            .build();

    Blob compositeObject = storage.compose(composeRequest);

    System.out.println(
        "New composite object "
            + compositeObject.getName()
            + " was created by combining "
            + firstObjectName
            + " and "
            + secondObjectName);
  }
}

Node.js

如需了解详情，请参阅 Cloud Storage Node.js API 参考文档。

如需向 Cloud Storage 进行身份验证，请设置应用默认凭据。 如需了解详情，请参阅为客户端库设置身份验证。 

/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
// The ID of your GCS bucket
// const bucketName = 'your-unique-bucket-name';

// The ID of the first GCS file to compose
// const firstFileName = 'your-first-file-name';

// The ID of the second GCS file to compose
// const secondFileName = 'your-second-file-name';

// The ID to give the new composite file
// const destinationFileName = 'new-composite-file-name';

// Imports the Google Cloud client library
const {Storage} = require('@google-cloud/storage');

// Creates a client
const storage = new Storage();

async function composeFile() {
  const bucket = storage.bucket(bucketName);
  const sources = [firstFileName, secondFileName];

  // Optional:
  // Set a generation-match precondition to avoid potential race conditions
  // and data corruptions. The request to compose is aborted if the object's
  // generation number does not match your precondition. For a destination
  // object that does not yet exist, set the ifGenerationMatch precondition to 0
  // If the destination object already exists in your bucket, set instead a
  // generation-match precondition using its generation number.
  const combineOptions = {
    ifGenerationMatch: destinationGenerationMatchPrecondition,
  };
  await bucket.combine(sources, destinationFileName, combineOptions);

  console.log(
    `New composite file ${destinationFileName} was created by combining ${firstFileName} and ${secondFileName}`
  );
}

composeFile().catch(console.error);

PHP

如需了解详情，请参阅 Cloud Storage PHP API 参考文档。

如需向 Cloud Storage 进行身份验证，请设置应用默认凭据。 如需了解详情，请参阅为客户端库设置身份验证。 

use Google\Cloud\Storage\StorageClient;

/**
 * Compose two objects into a single target object.
 *
 * @param string $bucketName The name of your Cloud Storage bucket.
 *        (e.g. 'my-bucket')
 * @param string $firstObjectName The name of the first GCS object to compose.
 *        (e.g. 'my-object-1')
 * @param string $secondObjectName The name of the second GCS object to compose.
 *        (e.g. 'my-object-2')
 * @param string $targetObjectName The name of the object to be created.
 *        (e.g. 'composed-my-object-1-my-object-2')
 */
function compose_file(string $bucketName, string $firstObjectName, string $secondObjectName, string $targetObjectName): void
{
    $storage = new StorageClient();
    $bucket = $storage->bucket($bucketName);

    // In this example, we are composing only two objects, but Cloud Storage supports
    // composition of up to 32 objects.
    $objectsToCompose = [$firstObjectName, $secondObjectName];

    $targetObject = $bucket->compose($objectsToCompose, $targetObjectName, [
        'destination' => [
            'contentType' => 'application/octet-stream'
        ]
    ]);

    if ($targetObject->exists()) {
        printf(
            'New composite object %s was created by combining %s and %s',
            $targetObject->name(),
            $firstObjectName,
            $secondObjectName
        );
    }
}

Python

如需了解详情，请参阅 Cloud Storage Python API 参考文档。

如需向 Cloud Storage 进行身份验证，请设置应用默认凭据。 如需了解详情，请参阅为客户端库设置身份验证。 

from google.cloud import storage


def compose_file(bucket_name, first_blob_name, second_blob_name, destination_blob_name):
    """Concatenate source blobs into destination blob."""
    # bucket_name = "your-bucket-name"
    # first_blob_name = "first-object-name"
    # second_blob_name = "second-blob-name"
    # destination_blob_name = "destination-object-name"

    storage_client = storage.Client()
    bucket = storage_client.bucket(bucket_name)
    destination = bucket.blob(destination_blob_name)
    destination.content_type = "text/plain"

    # Note sources is a list of Blob instances, up to the max of 32 instances per request
    sources = [bucket.blob(first_blob_name), bucket.blob(second_blob_name)]

    # Optional: set a generation-match precondition to avoid potential race conditions
    # and data corruptions. The request to compose is aborted if the object's
    # generation number does not match your precondition. For a destination
    # object that does not yet exist, set the if_generation_match precondition to 0.
    # If the destination object already exists in your bucket, set instead a
    # generation-match precondition using its generation number.
    # There is also an `if_source_generation_match` parameter, which is not used in this example.
    destination_generation_match_precondition = 0

    destination.compose(sources, if_generation_match=destination_generation_match_precondition)

    print(
        "New composite object {} in the bucket {} was created by combining {} and {}".format(
            destination_blob_name, bucket_name, first_blob_name, second_blob_name
        )
    )
    return destination

Ruby

如需了解详情，请参阅 Cloud Storage Ruby API 参考文档。

如需向 Cloud Storage 进行身份验证，请设置应用默认凭据。 如需了解详情，请参阅为客户端库设置身份验证。 

def compose_file bucket_name:, first_file_name:, second_file_name:, destination_file_name:
  # The ID of your GCS bucket
  # bucket_name = "your-unique-bucket-name"

  # The ID of the first GCS object to compose
  # first_file_name = "your-first-file-name"

  # The ID of the second GCS object to compose
  # second_file_name = "your-second-file-name"

  # The ID to give the new composite object
  # destination_file_name = "new-composite-file-name"

  require "google/cloud/storage"

  storage = Google::Cloud::Storage.new
  bucket = storage.bucket bucket_name, skip_lookup: true

  destination = bucket.compose [first_file_name, second_file_name], destination_file_name do |f|
    f.content_type = "text/plain"
  end

  puts "Composed new file #{destination.name} in the bucket #{bucket_name} " \
       "by combining #{first_file_name} and #{second_file_name}"
end

REST API

JSON API

  1. 安装并初始化 gcloud CLI，以便为 Authorization 标头生成访问令牌。

  2. 创建一个包含以下信息的 JSON 文件： 

    {
  "sourceObjects": [
    {
      "name": "SOURCE_OBJECT_1"
    },
    {
      "name": "SOURCE_OBJECT_2"
    }
  ],
  "destination": {
    "contentType": "COMPOSITE_OBJECT_CONTENT_TYPE"
  }
}

    其中：

  3. 使用 cURL，通过 POST Object 请求调用 JSON API：

    curl -X POST --data-binary @JSON_FILE_NAME \
  -H "Authorization: Bearer $(gcloud auth print-access-token)" \
  -H "Content-Type: application/json" \
  "https://storage.googleapis.com/storage/v1/b/BUCKET_NAME/o/COMPOSITE_OBJECT_NAME/compose"

    其中：

    • JSON_FILE_NAME 是您在上一步中创建的文件的名称。
    • BUCKET_NAME 是包含源对象的存储分区的名称。
    • COMPOSITE_OBJECT_NAME 是您赋予对象组合成果的名称。

如果成功，系统会响应生成的复合对象的对象资源。

XML API

  1. 安装并初始化 gcloud CLI，以便为 Authorization 标头生成访问令牌。

  2. 创建一个包含以下信息的 XML 文件： 

      <ComposeRequest>
    <Component>
      <Name>SOURCE_OBJECT_1</Name>
    </Component>
    <Component>
      <Name>SOURCE_OBJECT_2</Name>
    </Component>
  </ComposeRequest>

    其中：

    • SOURCE_OBJECT_1 和 SOURCE_OBJECT_2 是对象组合过程中使用的源对象的名称。

  3. 使用 cURL，通过 PUT Object 请求和 compose 查询字符串参数调用 XML API：

    curl -X PUT --data-binary @XML_FILE_NAME \
  -H "Authorization: Bearer $(gcloud auth print-access-token)" \
  -H "Content-Type: COMPOSITE_OBJECT_CONTENT_TYPE" \
  "https://storage.googleapis.com/BUCKET_NAME/COMPOSITE_OBJECT_NAME?compose"

    其中：

    • XML_FILE_NAME 是您在上一步中创建的文件的名称。
    • COMPOSITE_OBJECT_CONTENT_TYPE 是生成的复合对象的 Content-Type。
    • BUCKET_NAME 是包含源对象的存储分区的名称。
    • COMPOSITE_OBJECT_NAME 是您赋予对象组合成果的名称。

如果成功，则返回空的响应正文。

后续步骤