Änderungen abrufen

Für Google Drive-Anwendungen, die Änderungen an Dateien verfolgen müssen, bietet die Sammlung changes eine effiziente Möglichkeit, alle Dateiänderungen zu erkennen, auch solche, die für einen Nutzer freigegeben wurden. Wenn sich die Datei geändert hat, liefert die Sammlung den aktuellen Status jeder Datei.

Startseitentoken abrufen

Mit changes.getStartPageToken fordern Sie das Seitentoken für den aktuellen Status des Kontos an. Speichern und verwenden Sie dieses Token beim ersten Aufruf von changes.list.

So rufen Sie das Token der aktuellen Seite ab:

Java

drive/snippets/drive_v3/src/main/java/FetchStartPageToken.java

Auf GitHub ansehen

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.api.services.drive.model.StartPageToken;
import com.google.auth.http.HttpCredentialsAdapter;
import com.google.auth.oauth2.GoogleCredentials;
import java.io.IOException;
import java.util.Arrays;

/* Class to demonstrate use-case of Drive's fetch start page token */
public class FetchStartPageToken {

  /**
   * Retrieve the start page token for the first time.
   *
   * @return Start page token as String.
   * @throws IOException if file is not found
   */
  public static String fetchStartPageToken() 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 {
      StartPageToken response = service.changes()
          .getStartPageToken().execute();
      System.out.println("Start token: " + response.getStartPageToken());

      return response.getStartPageToken();
    } catch (GoogleJsonResponseException e) {
      // TODO(developer) - handle error appropriately
      System.err.println("Unable to fetch start page token: " + e.getDetails());
      throw e;
    }
  }

}

Python

drive/snippets/drive-v3/change_snippet/fetch_start_page_token.py

Auf GitHub ansehen

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


def fetch_start_page_token():
  """Retrieve page token for the current state of the account.
  Returns & prints : start page token

  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)

    # pylint: disable=maybe-no-member
    response = service.changes().getStartPageToken().execute()
    print(f'Start token: {response.get("startPageToken")}')

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

  return response.get("startPageToken")


if __name__ == "__main__":
  fetch_start_page_token()

PHP

drive/snippets/drive_v3/src/DriveFetchStartPageToken.php

Auf GitHub ansehen

use Google\Client;
use Google\Service\Drive;
# TODO - PHP client currently chokes on fetching start page token
function fetchStartPageToken()
{
    try {
        $client = new Client();
        $client->useApplicationDefaultCredentials();
        $client->addScope(Drive::DRIVE);
        $driveService = new Drive($client);
        $response = $driveService->changes->getStartPageToken();
        printf("Start token: %s\n", $response->startPageToken);
        return $response->startPageToken;
    } catch(Exception $e) {
        echo "Error Message: ".$e;
    }

}

.NET

drive/snippets/drive_v3/DriveV3Snippets/FetchStartPageToken.cs

Auf GitHub ansehen

using Google.Apis.Auth.OAuth2;
using Google.Apis.Drive.v3;
using Google.Apis.Services;

namespace DriveV3Snippets
{
    // Class to demonstrate use-case of Drive's fetch start page token
    public class FetchStartPageToken
    {
        /// <summary>
        /// Retrieve the starting page token.
        /// </summary>
        /// <returns>start page token as String, null otherwise.</returns>
        public static string DriveFetchStartPageToken()
        {
            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 response = service.Changes.GetStartPageToken().Execute();
                // Prints the token value.
                Console.WriteLine("Start token: " + response.StartPageTokenValue);
                return response.StartPageTokenValue;
            }
            catch (Exception e)
            {
                // TODO(developer) - handle error appropriately
                if (e is AggregateException)
                {
                    Console.WriteLine("Credential Not found");
                }
                else
                {
                    throw;
                }
            }
            return null;
        }
    }
}

Node.js

drive/snippets/drive_v3/change_snippets/fetch_start_page_token.js

Auf GitHub ansehen

/**
 * Retrieve page token for the current state of the account.
 **/
async function fetchStartPageToken() {
  // 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.appdata',
  });
  const service = google.drive({version: 'v3', auth});
  try {
    const res = await service.changes.getStartPageToken({});
    const token = res.data.startPageToken;
    console.log('start token: ', token);
    return token;
  } catch (err) {
    // TODO(developer) - Handle error
    throw err;
  }
}

Änderungen abrufen

Wenn Sie die Liste der Änderungen für den aktuell angemeldeten Nutzer abrufen möchten, senden Sie eine GET-Anfrage an die Sammlung changes, wie in changes.list beschrieben.

Die Einträge in der Sammlung changes sind in chronologischer Reihenfolge sortiert (die ältesten Änderungen werden zuerst angezeigt). Die Abfrageparameter includeRemoved und restrictToMyDrive bestimmen, ob die Antwort entfernte oder freigegebene Elemente enthalten soll.

Java

drive/snippets/drive_v3/src/main/java/FetchChanges.java

Auf GitHub ansehen

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.api.services.drive.model.ChangeList;
import com.google.auth.http.HttpCredentialsAdapter;
import com.google.auth.oauth2.GoogleCredentials;
import java.io.IOException;
import java.util.Arrays;

/* Class to demonstrate use-case of Drive's fetch changes in file. */
public class FetchChanges {
  /**
   * Retrieve the list of changes for the currently authenticated user.
   *
   * @param savedStartPageToken Last saved start token for this user.
   * @return Saved token after last page.
   * @throws IOException if file is not found
   */
  public static String fetchChanges(String savedStartPageToken) 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 {
      // Begin with our last saved start token for this user or the
      // current token from getStartPageToken()
      String pageToken = savedStartPageToken;
      while (pageToken != null) {
        ChangeList changes = service.changes().list(pageToken)
            .execute();
        for (com.google.api.services.drive.model.Change change : changes.getChanges()) {
          // Process change
          System.out.println("Change found for file: " + change.getFileId());
        }
        if (changes.getNewStartPageToken() != null) {
          // Last page, save this token for the next polling interval
          savedStartPageToken = changes.getNewStartPageToken();
        }
        pageToken = changes.getNextPageToken();
      }

      return savedStartPageToken;
    } catch (GoogleJsonResponseException e) {
      // TODO(developer) - handle error appropriately
      System.err.println("Unable to fetch changes: " + e.getDetails());
      throw e;
    }
  }
}

Python

drive/snippets/drive-v3/change_snippet/fetch_changes.py

Auf GitHub ansehen

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


def fetch_changes(saved_start_page_token):
  """Retrieve the list of changes for the currently authenticated user.
      prints changed file's ID
  Args:
      saved_start_page_token : StartPageToken for the current state of the
      account.
  Returns: saved start page token.

  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)

    # Begin with our last saved start token for this user or the
    # current token from getStartPageToken()
    page_token = saved_start_page_token
    # pylint: disable=maybe-no-member

    while page_token is not None:
      response = (
          service.changes().list(pageToken=page_token, spaces="drive").execute()
      )
      for change in response.get("changes"):
        # Process change
        print(f'Change found for file: {change.get("fileId")}')
      if "newStartPageToken" in response:
        # Last page, save this token for the next polling interval
        saved_start_page_token = response.get("newStartPageToken")
      page_token = response.get("nextPageToken")

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

  return saved_start_page_token


if __name__ == "__main__":
  # saved_start_page_token is the token number
  fetch_changes(saved_start_page_token=209)

PHP

drive/snippets/drive_v3/src/DriveFetchChanges.php

Auf GitHub ansehen

use Google\Client;
use Google\Service\Drive;
# TODO - PHP client currently chokes on fetching start page token
function fetchChanges()
{
    try {
        $client = new Client();
        $client->useApplicationDefaultCredentials();
        $client->addScope(Drive::DRIVE);
        $driveService = new Drive($client);
        # Begin with our last saved start token for this user or the
        # current token from getStartPageToken()
        $savedStartPageToken = readLine("Enter Start Page Token: ");
        $pageToken = $savedStartPageToken;
        while ($pageToken != null) {
            $response = $driveService->changes->listChanges($pageToken, array(
                'spaces' => 'drive'
            ));
            foreach ($response->changes as $change) {
                // Process change
                printf("Change found for file: %s", $change->fileId);
            }
            if ($response->newStartPageToken != null) {
                // Last page, save this token for the next polling interval
                $savedStartPageToken = $response->newStartPageToken;
            }
            $pageToken = $response->nextPageToken;
        }
        echo $savedStartPageToken;
    } catch(Exception $e) {
        echo "Error Message: ".$e;
    }

}
require_once 'vendor/autoload.php';

.NET

drive/snippets/drive_v3/DriveV3Snippets/FetchChanges.cs

Auf GitHub ansehen

using Google.Apis.Auth.OAuth2;
using Google.Apis.Drive.v3;
using Google.Apis.Services;

namespace DriveV3Snippets
{
    // Class to demonstrate use-case of Drive's fetch changes in file.
    public class FetchChanges
    {
        /// <summary>
        /// Retrieve the list of changes for the currently authenticated user.
        /// prints changed file's ID
        /// </summary>
        /// <param name="savedStartPageToken">last saved start token for this user.</param>
        /// <returns>saved token for the current state of the account, null otherwise.</returns>
        public static string DriveFetchChanges(string savedStartPageToken)
        {
            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"
                });

                // Begin with our last saved start token for this user or the
                // current token from GetStartPageToken()
                string pageToken = savedStartPageToken;
                while (pageToken != null)
                {
                    var request = service.Changes.List(pageToken);
                    request.Spaces = "drive";
                    var changes = request.Execute();
                    foreach (var change in changes.Changes)
                    {
                        // Process change
                        Console.WriteLine("Change found for file: " + change.FileId);
                    }

                    if (changes.NewStartPageToken != null)
                    {
                        // Last page, save this token for the next polling interval
                        savedStartPageToken = changes.NewStartPageToken;
                    }
                    pageToken = changes.NextPageToken;
                }
                return savedStartPageToken;
            }
            catch (Exception e)
            {
                // TODO(developer) - handle error appropriately
                if (e is AggregateException)
                {
                    Console.WriteLine("Credential Not found");
                }
                else
                {
                    throw;
                }
            }
            return null;
        }
    }
}

Node.js

drive/snippets/drive_v3/change_snippets/fetch_changes.js

Auf GitHub ansehen

/**
 * Retrieve the list of changes for the currently authenticated user.
 * @param {string} savedStartPageToken page token got after executing fetch_start_page_token.js file
 **/
async function fetchChanges(savedStartPageToken) {
  // 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.readonly',
  });
  const service = google.drive({version: 'v3', auth});
  try {
    let pageToken = savedStartPageToken;
    do {
      const res = await service.changes.list({
        pageToken: savedStartPageToken,
        fields: '*',
      });
      res.data.changes.forEach((change) => {
        console.log('change found for file: ', change.fileId);
      });
      pageToken = res.data.newStartPageToken;
      return pageToken;
    } while (pageToken);
  } catch (err) {
    // TODO(developer) - Handle error
    throw err;
  }
}

Die Sammlung changes in der Antwort kann eine nextPageToken enthalten. Wenn nextPageToken aufgeführt ist, kann damit die nächste Seite mit Änderungen erfasst werden. Ist dies nicht der Fall, sollte die Clientanwendung den newStartPageToken zur späteren Verwendung in der Antwort speichern. Wenn das Seitentoken gespeichert ist, kann die Clientanwendung eine erneute Abfrage für zukünftige Änderungen ausführen.

Benachrichtigungen erhalten

Verwenden Sie die Methode changes.watch, um Aktualisierungen im Änderungsprotokoll zu abonnieren. Benachrichtigungen enthalten keine Details zu den Änderungen. Stattdessen weisen sie darauf hin, dass neue Änderungen verfügbar sind. Wenn Sie die tatsächlichen Änderungen abrufen möchten, fragen Sie den Änderungsfeed wie unter Änderungen abrufen beschrieben ab.

Hinweis: Obwohl die Methode nicht in changes.watch dokumentiert ist, erfordert sie einen pageToken-Parameter ähnlich wie changes.list. Dies kann aus changes.getStartPageToken abgerufen werden.

Weitere Informationen finden Sie unter Benachrichtigungen für Ressourcenänderungen.