下载和导出文件

Google Drive API 支持多种类型的下载和导出操作，例如 如下表所示：

下载内容
将 files.get 方法与 alt=media 网址参数搭配使用的 Blob 文件内容。
将 revisions.get 方法与 alt=media 网址参数搭配使用时，较早版本的 Blob 文件内容。
使用 webContentLink 字段的浏览器中的 Blob 文件内容。
导出内容
使用 files.export 以您的应用能够处理的格式 Google Workspace 文档内容。
使用 exportLinks 字段在浏览器中查看 Google Workspace 文档内容。
在浏览器中使用 exportLinks 字段查看较早版本的 Google Workspace 文档内容。

在下载或导出文件内容之前，请验证用户是否能够下载 使用 capabilities.canDownload 字段指定文件 files 资源。

本指南的其余部分提供了执行这些类型的详细说明 下载和导出操作的详细信息。

下载 blob 文件内容

如需下载存储在云端硬盘中的 blob 文件，请使用 files.get 方法并提供要下载的文件的 ID 和 alt=media 网址参数。alt=media 网址参数用于告知 作为备用响应请求下载内容的服务器 格式。

alt=media 网址参数是一个系统参数 参数 适用于所有 Google REST API。如果您使用客户端库 Drive API 的相关操作说明，您无需明确设置此参数。

以下代码示例展示了如何使用 files.get 方法下载 文件。

Java

drive/snippets/drive_v3/src/main/java/DownloadFile.java
import com.google.api.client.googleapis.json.GoogleJsonResponseException;
import com.google.api.client.http.HttpRequestInitializer;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.gson.GsonFactory;
import com.google.api.services.drive.Drive;
import com.google.api.services.drive.DriveScopes;
import com.google.auth.http.HttpCredentialsAdapter;
import com.google.auth.oauth2.GoogleCredentials;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;

/* Class to demonstrate use-case of drive's download file. */
public class DownloadFile {

  /**
   * Download a Document file in PDF format.
   *
   * @param realFileId file ID of any workspace document format file.
   * @return byte array stream if successful, {@code null} otherwise.
   * @throws IOException if service account credentials file not found.
   */
  public static ByteArrayOutputStream downloadFile(String realFileId) throws IOException {
        /* Load pre-authorized user credentials from the environment.
           TODO(developer) - See https://developers.google.com/identity for
          guides on implementing OAuth2 for your application.*/
    GoogleCredentials credentials = GoogleCredentials.getApplicationDefault()
        .createScoped(Arrays.asList(DriveScopes.DRIVE_FILE));
    HttpRequestInitializer requestInitializer = new HttpCredentialsAdapter(
        credentials);

    // Build a new authorized API client service.
    Drive service = new Drive.Builder(new NetHttpTransport(),
        GsonFactory.getDefaultInstance(),
        requestInitializer)
        .setApplicationName("Drive samples")
        .build();

    try {
      OutputStream outputStream = new ByteArrayOutputStream();

      service.files().get(realFileId)
          .executeMediaAndDownloadTo(outputStream);

      return (ByteArrayOutputStream) outputStream;
    } catch (GoogleJsonResponseException e) {
      // TODO(developer) - handle error appropriately
      System.err.println("Unable to move file: " + e.getDetails());
      throw e;
    }
  }
}

Python

drive/snippets/drive-v3/file_snippet/download_file.py
import io

import google.auth
from googleapiclient.discovery import build
from googleapiclient.errors import HttpError
from googleapiclient.http import MediaIoBaseDownload


def download_file(real_file_id):
  """Downloads a file
  Args:
      real_file_id: ID of the file to download
  Returns : IO object with location.

  Load pre-authorized user credentials from the environment.
  TODO(developer) - See https://developers.google.com/identity
  for guides on implementing OAuth2 for the application.
  """
  creds, _ = google.auth.default()

  try:
    # create drive api client
    service = build("drive", "v3", credentials=creds)

    file_id = real_file_id

    # pylint: disable=maybe-no-member
    request = service.files().get_media(fileId=file_id)
    file = io.BytesIO()
    downloader = MediaIoBaseDownload(file, request)
    done = False
    while done is False:
      status, done = downloader.next_chunk()
      print(f"Download {int(status.progress() * 100)}.")

  except HttpError as error:
    print(f"An error occurred: {error}")
    file = None

  return file.getvalue()


if __name__ == "__main__":
  download_file(real_file_id="1KuPmvGq8yoYgbfW74OENMCB5H0n_2Jm9")

Node.js

drive/snippets/drive_v3/file_snippets/download_file.js
/**
 * Downloads a file
 * @param{string} realFileId file ID
 * @return{obj} file status
 * */
async function downloadFile(realFileId) {
  // Get credentials and build service
  // TODO (developer) - Use appropriate auth mechanism for your app

  const {GoogleAuth} = require('google-auth-library');
  const {google} = require('googleapis');

  const auth = new GoogleAuth({
    scopes: 'https://www.googleapis.com/auth/drive',
  });
  const service = google.drive({version: 'v3', auth});

  fileId = realFileId;
  try {
    const file = await service.files.get({
      fileId: fileId,
      alt: 'media',
    });
    console.log(file.status);
    return file.status;
  } catch (err) {
    // TODO(developer) - Handle error
    throw err;
  }
}

PHP

drive/snippets/drive_v3/src/DriveDownloadFile.php
use Google\Client;
use Google\Service\Drive;
function downloadFile()
 {
    try {

      $client = new Client();
      $client->useApplicationDefaultCredentials();
      $client->addScope(Drive::DRIVE);
      $driveService = new Drive($client);
      $realFileId = readline("Enter File Id: ");
      $fileId = '0BwwA4oUTeiV1UVNwOHItT0xfa2M';
      $fileId = $realFileId;
      $response = $driveService->files->get($fileId, array(
          'alt' => 'media'));
      $content = $response->getBody()->getContents();
      return $content;

    } catch(Exception $e) {
      echo "Error Message: ".$e;
    }

}

.NET

drive/snippets/drive_v3/DriveV3Snippets/DownloadFile.cs
using Google.Apis.Auth.OAuth2;
using Google.Apis.Download;
using Google.Apis.Drive.v3;
using Google.Apis.Services;

namespace DriveV3Snippets
{
    // Class to demonstrate use-case of drive's download file.
    public class DownloadFile
    {
        /// <summary>
        /// Download a Document file in PDF format.
        /// </summary>
        /// <param name="fileId">file ID of any workspace document format file.</param>
        /// <returns>byte array stream if successful, null otherwise.</returns>
        public static MemoryStream DriveDownloadFile(string fileId)
        {
            try
            {
                /* Load pre-authorized user credentials from the environment.
                 TODO(developer) - See https://developers.google.com/identity for 
                 guides on implementing OAuth2 for your application. */
                GoogleCredential credential = GoogleCredential
                    .GetApplicationDefault()
                    .CreateScoped(DriveService.Scope.Drive);

                // Create Drive API service.
                var service = new DriveService(new BaseClientService.Initializer
                {
                    HttpClientInitializer = credential,
                    ApplicationName = "Drive API Snippets"
                });

                var request = service.Files.Get(fileId);
                var stream = new MemoryStream();

                // Add a handler which will be notified on progress changes.
                // It will notify on each chunk download and when the
                // download is completed or failed.
                request.MediaDownloader.ProgressChanged +=
                    progress =>
                    {
                        switch (progress.Status)
                        {
                            case DownloadStatus.Downloading:
                            {
                                Console.WriteLine(progress.BytesDownloaded);
                                break;
                            }
                            case DownloadStatus.Completed:
                            {
                                Console.WriteLine("Download complete.");
                                break;
                            }
                            case DownloadStatus.Failed:
                            {
                                Console.WriteLine("Download failed.");
                                break;
                            }
                        }
                    };
                request.Download(stream);

                return stream;
            }
            catch (Exception e)
            {
                // TODO(developer) - handle error appropriately
                if (e is AggregateException)
                {
                    Console.WriteLine("Credential Not found");
                }
                else
                {
                    throw;
                }
            }
            return null;
        }
    }
}

此代码示例使用的库方法会添加 alt=media 网址参数 基础 HTTP 请求。

从您的应用开始的文件下载必须经过授权，授权范围允许 拥有文件内容的读取权限。例如，使用 drive.readonly.metadata 范围无权下载文件内容。 此代码示例使用受限的“drive”文件范围，允许用户 查看和管理您的所有云端硬盘文件。要详细了解 云端硬盘范围，请参阅选择 Google Drive API 范围。

拥有修改权限的用户可以通过以下方式限制只读用户的下载： 设置 copyRequiresWriterPermission 字段设置为 false。

文件被标识为 有滥用行为 （例如有害软件）。 此外，还必须包含 get 查询参数 acknowledgeAbuse=true 表示用户已知晓 垃圾软件或其他存在滥用行为的文件您的应用应以交互方式 在使用此查询参数前警告用户。

已下载部分内容

部分下载是指仅下载文件的指定部分。您 可以使用字节 续航里程 标头为 Range。例如：

Range: bytes=500-999

下载较低版本的 blob 文件内容

要下载较早版本的 blob 文件的内容，请使用 revisions.get 方法，其 ID 为 要下载的文件、修订版本的 ID 和 alt=media 网址参数。 alt=media 网址参数告知服务器某下载内容已被下载 作为备用响应格式。与 files.get 类似， revisions.get 方法还接受可选的查询参数 acknowledgeAbuse 和 Range 标头。如需详细了解如何下载 请参阅下载和发布文件 修订版本。

在浏览器中下载 blob 文件内容

如要以单个文件的形式下载存储在云端硬盘上的 blob 文件的内容， 而不是通过 API，请使用 webContentLink 字段的 files 资源。如果用户有下载内容 访问文件的链接，点击此链接下载相应文件及其内容 返回。您可以将用户重定向到此网址，也可以将其作为可点击的网址提供 链接。

导出 Google Workspace 文档内容

如需导出 Google Workspace 文档字节内容，请使用 files.export 方法并提供要导出的文件的 ID 以及正确的 MIME 类型。已导出 内容不得超过 10 MB。

以下代码示例展示了如何使用 files.export 方法导出 使用 Drive API 客户端的 PDF 格式的 Google Workspace 文档 库：

Java

drive/snippets/drive_v3/src/main/java/ExportPdf.java
import com.google.api.client.googleapis.json.GoogleJsonResponseException;
import com.google.api.client.http.HttpRequestInitializer;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.gson.GsonFactory;
import com.google.api.services.drive.Drive;
import com.google.api.services.drive.DriveScopes;
import com.google.auth.http.HttpCredentialsAdapter;
import com.google.auth.oauth2.GoogleCredentials;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Arrays;

/* Class to demonstrate use-case of drive's export pdf. */
public class ExportPdf {

  /**
   * Download a Document file in PDF format.
   *
   * @param realFileId file ID of any workspace document format file.
   * @return byte array stream if successful, {@code null} otherwise.
   * @throws IOException if service account credentials file not found.
   */
  public static ByteArrayOutputStream exportPdf(String realFileId) throws IOException {
    // Load pre-authorized user credentials from the environment.
    // TODO(developer) - See https://developers.google.com/identity for
    // guides on implementing OAuth2 for your application.
    GoogleCredentials credentials = GoogleCredentials.getApplicationDefault()
        .createScoped(Arrays.asList(DriveScopes.DRIVE_FILE));
    HttpRequestInitializer requestInitializer = new HttpCredentialsAdapter(
        credentials);

    // Build a new authorized API client service.
    Drive service = new Drive.Builder(new NetHttpTransport(),
        GsonFactory.getDefaultInstance(),
        requestInitializer)
        .setApplicationName("Drive samples")
        .build();

    OutputStream outputStream = new ByteArrayOutputStream();
    try {
      service.files().export(realFileId, "application/pdf")
          .executeMediaAndDownloadTo(outputStream);

      return (ByteArrayOutputStream) outputStream;
    } catch (GoogleJsonResponseException e) {
      // TODO(developer) - handle error appropriately
      System.err.println("Unable to export file: " + e.getDetails());
      throw e;
    }
  }
}

Python

drive/snippets/drive-v3/file_snippet/export_pdf.py
import io

import google.auth
from googleapiclient.discovery import build
from googleapiclient.errors import HttpError
from googleapiclient.http import MediaIoBaseDownload


def export_pdf(real_file_id):
  """Download a Document file in PDF format.
  Args:
      real_file_id : file ID of any workspace document format file
  Returns : IO object with location

  Load pre-authorized user credentials from the environment.
  TODO(developer) - See https://developers.google.com/identity
  for guides on implementing OAuth2 for the application.
  """
  creds, _ = google.auth.default()

  try:
    # create drive api client
    service = build("drive", "v3", credentials=creds)

    file_id = real_file_id

    # pylint: disable=maybe-no-member
    request = service.files().export_media(
        fileId=file_id, mimeType="application/pdf"
    )
    file = io.BytesIO()
    downloader = MediaIoBaseDownload(file, request)
    done = False
    while done is False:
      status, done = downloader.next_chunk()
      print(f"Download {int(status.progress() * 100)}.")

  except HttpError as error:
    print(f"An error occurred: {error}")
    file = None

  return file.getvalue()


if __name__ == "__main__":
  export_pdf(real_file_id="1zbp8wAyuImX91Jt9mI-CAX_1TqkBLDEDcr2WeXBbKUY")

Node.js

drive/snippets/drive_v3/file_snippets/export_pdf.js
/**
 * Download a Document file in PDF format
 * @param{string} fileId file ID
 * @return{obj} file status
 * */
async function exportPdf(fileId) {
  const {GoogleAuth} = require('google-auth-library');
  const {google} = require('googleapis');

  // Get credentials and build service
  // TODO (developer) - Use appropriate auth mechanism for your app
  const auth = new GoogleAuth({
    scopes: 'https://www.googleapis.com/auth/drive',
  });
  const service = google.drive({version: 'v3', auth});

  try {
    const result = await service.files.export({
      fileId: fileId,
      mimeType: 'application/pdf',
    });
    console.log(result.status);
    return result;
  } catch (err) {
    // TODO(developer) - Handle error
    throw err;
  }
}

PHP

drive/snippets/drive_v3/src/DriveExportPdf.php
use Google\Client;
use Google\Service\Drive;
function exportPdf()
{
    try {
        $client = new Client();
        $client->useApplicationDefaultCredentials();
        $client->addScope(Drive::DRIVE);
        $driveService = new Drive($client);
        $realFileId = readline("Enter File Id: ");
        $fileId = '1ZdR3L3qP4Bkq8noWLJHSr_iBau0DNT4Kli4SxNc2YEo';
        $fileId = $realFileId;
        $response = $driveService->files->export($fileId, 'application/pdf', array(
            'alt' => 'media'));
        $content = $response->getBody()->getContents();
        return $content;

    }  catch(Exception $e) {
         echo "Error Message: ".$e;
    }

}

.NET

drive/snippets/drive_v3/DriveV3Snippets/ExportPdf.cs
using Google.Apis.Auth.OAuth2;
using Google.Apis.Download;
using Google.Apis.Drive.v3;
using Google.Apis.Services;

namespace DriveV3Snippets
{
    // Class to demonstrate use of Drive export pdf
    public class ExportPdf
    {
        /// <summary>
        /// Download a Document file in PDF format.
        /// </summary>
        /// <param name="fileId">Id of the file.</param>
        /// <returns>Byte array stream if successful, null otherwise</returns>
        public static MemoryStream DriveExportPdf(string fileId)
        {
            try
            {
                /* Load pre-authorized user credentials from the environment.
                 TODO(developer) - See https://developers.google.com/identity for 
                 guides on implementing OAuth2 for your application. */
                GoogleCredential credential = GoogleCredential.GetApplicationDefault()
                    .CreateScoped(DriveService.Scope.Drive);

                // Create Drive API service.
                var service = new DriveService(new BaseClientService.Initializer
                {
                    HttpClientInitializer = credential,
                    ApplicationName = "Drive API Snippets"
                });

                var request = service.Files.Export(fileId, "application/pdf");
                var stream = new MemoryStream();
                // Add a handler which will be notified on progress changes.
                // It will notify on each chunk download and when the
                // download is completed or failed.
                request.MediaDownloader.ProgressChanged +=
                    progress =>
                    {
                        switch (progress.Status)
                        {
                            case DownloadStatus.Downloading:
                            {
                                Console.WriteLine(progress.BytesDownloaded);
                                break;
                            }
                            case DownloadStatus.Completed:
                            {
                                Console.WriteLine("Download complete.");
                                break;
                            }
                            case DownloadStatus.Failed:
                            {
                                Console.WriteLine("Download failed.");
                                break;
                            }
                        }
                    };
                request.Download(stream);
                return stream;
            }
            catch (Exception e)
            {
                // TODO(developer) - handle error appropriately
                if (e is AggregateException)
                {
                    Console.WriteLine("Credential Not found");
                }
                else
                {
                    throw;
                }
            }
            return null;
        }
    }
}

此代码示例使用受限的 drive 范围，该范围允许用户查看和 管理您的所有云端硬盘文件。要详细了解 云端硬盘范围，请参阅选择 Google Drive API 范围。

该代码示例还将导出 MIME 类型声明为 application/pdf。对于 每种 Google Workspace 支持的所有导出 MIME 类型的完整列表 文档，请参阅导出 Google Workspace 的 MIME 类型 文档。

在浏览器中导出 Google Workspace 文档内容

如需在浏览器中导出 Google Workspace 文档内容，请使用 exportLinks 字段的 files 资源。视文件而定 类型，系统会为每个 MIME 返回下载文件的链接及其内容 可用的类型。您可以将用户重定向到某个网址，也可以将其作为 可点击的链接

在浏览器中以较早版本导出 Google Workspace 文档内容

如要导出 Google Workspace 文档中较早版本的 Google Workspace 文档内容，请执行以下操作： 请使用 revisions.get 方法 替换为要下载的文件的 ID 和修订版本的 ID。如果用户 文件的下载权限，一个用于下载文件及其内容的链接 返回。您可以将用户重定向到此网址，也可以将其作为可点击的网址提供 链接。