Загрузите файл в облачное хранилище Google через appengine

Наконец, я могу загрузить файл с клиентского конца в облачное хранилище Google через appengine.

Я предполагаю, что перед выполнением этих шагов у вас есть следующие вещи, готовые

• файл JSON из вашей учетной записи службы.
• создал корзину по умолчанию.

Шаг 1: Создайте сервлет, подобный этому

package XXXXXXXXX;

import java.io.IOException;
import java.io.InputStream;
import java.security.GeneralSecurityException;
import java.util.Arrays;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.api.client.http.InputStreamContent;
import com.google.api.services.storage.Storage;
import com.google.api.services.storage.model.ObjectAccessControl;
import com.google.api.services.storage.model.StorageObject;

import XXXXXXXXXXXXX.StorageFactory;

//@author Umesh Chauhan

/**
 * Save File to GCS
 *
 * @param fileName        File Name with format
 * @header Content-Type   "*/*"
 * @return file path
 * @throws Exception      Any Error during upload
 */
public class UploadFile extends HttpServlet
{

    private static final long serialVersionUID = 1L;
    private final String BUCKET = "YOUR BUCKET NAME";
    private int maxFileSize = 6 * 1024 * 1024;

    @Override
    protected void doOptions ( HttpServletRequest req, HttpServletResponse resp ) throws ServletException, IOException
    {
        // pre-flight request processing
        resp.setHeader ( "Access-Control-Allow-Origin", "*" );
        resp.setHeader ( "Access-Control-Allow-Methods", "*" );
        resp.setHeader ( "Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept" );
    }

    @Override
    public void doPost ( HttpServletRequest request, HttpServletResponse response )
            throws ServletException, java.io.IOException
    {

        try
        {
            String path = uploadFile ( request.getParameter ( "fileName" ), request.getContentType (),
                    request.getInputStream (), BUCKET, request.getInputStream ().available () );
            // Sending Response
            response.setStatus ( HttpServletResponse.SC_OK );
            response.getWriter ().write ( path );
            response.getWriter ().flush ();
            response.getWriter ().close ();

        }
        catch ( GeneralSecurityException e )
        {
            e.printStackTrace ();
        }
    }

    public String uploadFile ( String name, String contentType, InputStream input, String bucketName,
            int contentLength ) throws IOException, GeneralSecurityException
    {

        InputStreamContent contentStream = new InputStreamContent ( contentType, input );

        if ( contentLength < maxFileSize )
        {

            // It is done Automatically.
            /*
             * // Setting the length improves upload performance
             * contentStream.setLength ( contentLength );
             */

            StorageObject objectMetadata = new StorageObject ()
                    // Set the destination object name
                    .setName ( name )
                    // Set the access control list to publicly read-only
                    .setAcl ( Arrays.asList (
                            new ObjectAccessControl ().setEntity ( "allUsers" ).setRole ( "READER" ) ) );

            // Do the insert
            Storage client = StorageFactory.getService ();

            Storage.Objects.Insert insertRequest = client.objects ()
                    .insert ( bucketName, objectMetadata, contentStream );

            insertRequest.execute ();

            return "https://storage.cloud.google.com/" + BUCKET + "/" + name;
        }
        else
        {
            throw new GeneralSecurityException ( "File size canot be more then 6 MB !" );
        }
    }

    public void doGet ( HttpServletRequest request, HttpServletResponse response )
            throws ServletException, java.io.IOException
    {
        throw new ServletException ( "GET method used with " + getClass ().getName () + ": POST method required." );
    }

}

Шаг 2: Ваша Фабрика Хранения

package XXXXXXXXXXXX;

import java.io.IOException;
import java.net.URL;
import java.security.GeneralSecurityException;
import java.util.Collection;

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.JsonFactory;
import com.google.api.client.json.jackson2.JacksonFactory;
import com.google.api.services.storage.Storage;
import com.google.api.services.storage.StorageScopes;

//@author Umesh Chauhan 

public class StorageFactory
{

    private static Storage instance = null;

    public static synchronized Storage getService () throws IOException, GeneralSecurityException
    {
        if ( instance == null )
        {
            instance = buildService ();
        }
        return instance;
    }

    private static Storage buildService () throws IOException, GeneralSecurityException
    {

        HttpTransport transport = GoogleNetHttpTransport.newTrustedTransport ();
        JsonFactory jsonFactory = new JacksonFactory ();

        GoogleCredential credential = GoogleCredential.fromStream (
                new URL ( "HERE GOES THE URL FOR YOUR SERVICE ACCOUNT JSON - I USED GOOGLE DRIVE DIRECT DOWNLOAD LINK TO MY JSON FILE" )
                        .openStream () );

        // Depending on the environment that provides the default credentials
        // (for
        // example: Compute Engine, App Engine), the credentials may require us
        // to
        // specify the scopes we need explicitly. Check for this case, and
        // inject
        // the Cloud Storage scope if required.
        if ( credential.createScopedRequired () )
        {
            Collection<String> scopes = StorageScopes.all ();
            credential = credential.createScoped ( scopes );
        }

        return new Storage.Builder ( transport, jsonFactory, credential ).setApplicationName ( "YOUR PROJECT NAME" ).build ();
    }
}

Шаг 3: обновить вас web.xml

    <servlet>
        <servlet-name>UploadFile</servlet-name>
        <servlet-class>PACKAGE.UploadFile</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>UploadFile</servlet-name>
        <url-pattern>/uploadManager/UploadFile</url-pattern>  //Based on your original URL
    </servlet-mapping>