Accedere ai bucket di archiviazione di Data Transfer

Google fornisce raccolte ed esempi di codice per Google Cloud Storage. L'esempio Java relativo alla lettura di un file da un bucket di archiviazione cloud Ad Manager ti consente di capire come i componenti che hai impostato durante la configurazione dell'account influiscono sul tuo codice:

• Nome del progetto. Nome del progetto di Google Cloud Storage.

• Indirizzo email dell'account per i servizi. L'indirizzo email generato.

• File chiave .p12. Il file scaricato.

• Nome del bucket. Google fornisce questo nome al momento dell'abilitazione di una funzionalità che utilizza i bucket di archiviazione cloud Ad Manager.

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.security.GeneralSecurityException;
import java.util.Collections;

import com.google.api.client.googleapis.auth.oauth2.GoogleCredential;
import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.services.storage.Storage;
import com.google.api.services.storage.model.StorageObject;

public class GcsApiTest {
    /**
     * The name of the project under which the service account was created.
     * 
     * This information is displayed under the Google Developers Console.
     */
    private static final String PROJECT_NAME = "project name";

    /**
     * Developer Email address of the service account.
     * 
     * This email is generated upon creating a Service Account Client ID in your
     * Google Developers Console, and can be retrieved from the Credentials
     * page. 
     */
    private static final String SERVICE_ACCOUNT_EMAIL = "service account email address";

    /**
     * Bucket to use for storage operations.
     * 
     * The name of this bucket was provided to you by your Account
     * Manager. It likely has a name similar to "gdfp-12345678" or
     * "gdfp_cookieupload_12345678", depending on the Ad Manager add-on you're using.
     */
    private static final String BUCKET_NAME = "bucket name";

    /**
     * Google Cloud Storage OAuth 2.0 scope for read/write. This should
     * correspond to the access rights for your "View data transfer buckets"  
     * permission  for the bucket, and you cannot request access rights that are 
     * not granted via the permission.
     */
    private static final String STORAGE_SCOPE = 
        "https://www.googleapis.com/auth/devstorage.read_write";

    /**
     * Path to the key.p12 file providing access to the bucket.
     * 
     * This file is created when the service client ID is created. If you don't
     * have this file, you will need to generate a new client p12 key from the
     * Google Developers Console.
     */
    private static final String KEY_P12 = "path to .p12 key file";

    /** HTTP transport. */
    private HttpTransport httpTransport;
    private Storage storage;

    // constructor, sets up credentials and storage objects
    public GcsApiTest() {
	File p12File = new File(KEY_P12);

	try {
	    httpTransport = GoogleNetHttpTransport.newTrustedTransport();

	    GoogleCredential credential = new GoogleCredential.Builder()
		    .setTransport(httpTransport)
		    .setJsonFactory(JacksonFactory.getDefaultInstance())
		    .setServiceAccountId(SERVICE_ACCOUNT_EMAIL)
		    .setServiceAccountScopes(
			    Collections.singleton(STORAGE_SCOPE))
		    .setServiceAccountPrivateKeyFromP12File(p12File).build();
	    storage = new Storage.Builder(httpTransport,
		    JacksonFactory.getDefaultInstance(), credential)
		    .setApplicationName(PROJECT_NAME).build();
	} catch (GeneralSecurityException | IOException e1) {
	    e1.printStackTrace();
	    System.exit(1);
	}
    }

    /**
     * Method to return the name of the first file in the bucket.
     * 
     * @return the name of the file, or null if the bucket is empty
     * @throws IOException
     */
    public String GetFirstFile() throws IOException {
	Storage.Objects.List listObjects = storage.objects().list(BUCKET_NAME);
	listObjects.setMaxResults(5L);
	com.google.api.services.storage.model.Objects objects = listObjects
		.execute();

	// empty bucket?
	if (null == objects.getItems() || objects.getItems().isEmpty()) {
	    System.out.println("Bucket \"" + BUCKET_NAME
		    + "\" empty or invalid.");
	    return null;
	}

	StorageObject object = objects.getItems().get(0);
	System.out.println("First object in bucket: \"" + object.getName()
		+ "\".");
	return object.getName();
    }

    /**
     * Method to download the specified file from the storage bucket
     * 
     * @param filename
     *            Name of the file that should be downloaded.
     * @throws IOException
     */
    public void DownloadFile(String filename) throws IOException {
	Storage.Objects.Get getObject = storage.objects().get(BUCKET_NAME,
		filename);
	OutputStream os = new FileOutputStream(filename, true);
	getObject.getMediaHttpDownloader().setDirectDownloadEnabled(true);
	getObject.executeMediaAndDownloadTo(os);

	System.out.println("File \"" + filename + "\" downloaded.");
    }

    /**
     * Main method to execute the different tests.
     * 
     * @param args
     */
    public static void main(String[] args) {
	GcsApiTest gcsApiTest = new GcsApiTest();

	try {
	    String filename = gcsApiTest.GetFirstFile();
	    gcsApiTest.DownloadFile(filename);
	} catch (IOException e) {
	    System.out.println(e.getMessage());
	}
    }
}