下載及匯出檔案

Google Drive API 支援多種下載和匯出動作，如下表所示：

下載內容
使用 files.get 方法搭配 alt=media 網址參數使用 Blob 檔案內容。
搭配 alt=media 網址參數使用 revisions.get 方法，以舊版 Blob 檔案內容。
使用 webContentLink 欄位在瀏覽器中的 Blob 檔案內容。
匯出項目
Google Workspace 文件內容，採用應用程式可處理的格式，使用 files.export。
使用 exportLinks 欄位，在瀏覽器中使用 Google Workspace 文件內容。
在瀏覽器中使用 exportLinks 欄位，下載舊版 Google Workspace 文件的內容。

本指南的其餘部分提供如何執行這些下載和匯出動作的詳細操作說明。

下載 blob 檔案內容

如要下載儲存在雲端硬碟中的 blob 檔案，請使用 files.get 方法，並提供要下載檔案的 ID 和 alt=media 網址參數。alt=media 網址參數會告知伺服器正在要求下載內容做為替代回應格式。

alt=media 網址參數是所有 Google REST API 都可使用的系統參數。如果針對 Drive API 使用用戶端程式庫，則不需要明確設定這個參數。

以下程式碼範例說明如何使用 files.get 方法下載含有 Drive API 用戶端程式庫的檔案。

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
from __future__ import print_function

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;
        }
    }
}

這個程式碼範例使用程式庫方法，將 alt=media 網址參數新增至基礎 HTTP 要求。

從應用程式啟動的檔案下載作業都必須在允許讀取檔案內容的範圍進行授權。舉例來說，使用 drive.readonly.metadata 範圍的應用程式沒有下載檔案內容的權限。本程式碼範例使用受限制的「雲端硬碟」檔案範圍，讓使用者能查看及管理您所有的雲端硬碟檔案。如要進一步瞭解雲端硬碟範圍，請參閱 API 專屬授權和驗證資訊。

具有編輯權限的使用者可以將 copyRequiresWriterPermission 欄位設為 false，以限制唯讀使用者下載。

經判定為濫用 (例如有害軟體) 的檔案只能由檔案擁有者下載。此外，必須加入 get 查詢參數 acknowledgeAbuse=true，以表示使用者已確認使用者下載了可能有害的軟體或其他濫用檔案的風險。您的應用程式應該在使用這項查詢參數之前，以互動方式向使用者顯示警告。

部分下載

部分下載涉及僅下載檔案的特定部分。您可以使用位元組範圍搭配 Range 標頭，指定您要下載檔案的部分。例如：

Range: bytes=500-999

下載舊版本的 blob 檔案內容

如要下載舊版 blob 檔案的內容，請使用 revisions.get 方法，搭配要下載檔案的 ID、修訂版本 ID 和 alt=media 網址參數。alt=media 網址參數會告知伺服器您要下載內容做為替代回應格式。與 files.get 類似，revisions.get 方法也接受選用的查詢參數 acknowledgeAbuse 和 Range 標頭。如要進一步瞭解如何下載修訂版本，請參閱下載及發布檔案修訂版本。

在瀏覽器中下載 blob 檔案內容

如要下載在瀏覽器中儲存的 blob 檔案內容 (而非透過 API)，請使用 Files 資源的 webContentLink 欄位。如果使用者擁有檔案的下載權限，系統會傳回該檔案及其內容的下載連結。您可以將使用者重新導向至這個網址，也可以將其設為可點選的連結。

匯出 Google Workspace 文件內容

如要匯出 Google Workspace 文件位元組內容，請使用 files.export 方法，搭配要匯出的檔案 ID 以及正確的 MIME 類型。匯出的內容大小上限為 10 MB。

以下程式碼範例顯示如何利用 files.export 方法，透過 Drive API 用戶端程式庫以 PDF 格式匯出 Google Workspace 文件：

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
from __future__ import print_function

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;
        }
    }
}

這個程式碼範例使用了受限制的 drive 範圍，可讓使用者查看及管理所有雲端硬碟檔案。如要進一步瞭解雲端硬碟範圍，請參閱 API 專屬授權和驗證資訊。

這個程式碼範例也會將匯出的 MIME 類型宣告為 application/pdf。如需各項 Google Workspace 文件支援的所有匯出 MIME 類型完整清單，請參閱「匯出 Google Workspace 文件的 MIME 類型」。

在瀏覽器中匯出 Google Workspace 文件內容

如要在瀏覽器中匯出 Google Workspace 文件內容，請使用 Files 資源的 exportLinks 欄位。視文件類型而定，系統會針對可用的每種 MIME 類型傳回檔案下載連結及其內容。您可以將使用者重新導向至網址，或以可點擊連結的形式提供網址。

在瀏覽器中匯出舊版 Google Workspace 文件內容

如要在瀏覽器中匯出舊版 Google Workspace 文件內容，請使用 revisions.get 方法，搭配要下載檔案的 ID 和修訂版本 ID。如果使用者擁有檔案的下載權限，系統會傳回檔案下載連結及其內容。您可以將使用者重新導向至這個網址，也可以將其設為可點選的連結。