通过 appengine 将文件上传到 Google 云存储

Question

我正在尝试将文件上传到 Google 云存储。我的 Servlet 代码是

public class UploadFile extends HttpServlet {

    private final String BUCKET = "XXXXXXXXX";
       private boolean isMultipart;
       private String filePath;
       private int maxFileSize = 5 * 1024 * 1024;
       private int maxMemSize = 5 * 1024 * 1024;
       private File file ;

       public void init( ){
          // Get the file location where it would be stored.
          filePath = 
                 getServletContext().getInitParameter("file-upload"); 
       }
       public void doPost(HttpServletRequest request, 
                   HttpServletResponse response)
                  throws ServletException, java.io.IOException {
          // Check that we have a file upload request
          isMultipart = ServletFileUpload.isMultipartContent(request);
          response.setContentType("text/html");
          java.io.PrintWriter out = response.getWriter( );
          if( !isMultipart ){
             out.println("<html>");
             out.println("<head>");
             out.println("<title>Servlet upload</title>");  
             out.println("</head>");
             out.println("<body>");
             out.println("<p>No file uploaded</p>"); 
             out.println("</body>");
             out.println("</html>");
             return;
          }
          DiskFileItemFactory factory = new DiskFileItemFactory();
          // maximum size that will be stored in memory
          factory.setSizeThreshold(maxMemSize);
          // Location to save data that is larger than maxMemSize.
          factory.setRepository(new File("/temp/image/"));

          // Create a new file upload handler
          ServletFileUpload upload = new ServletFileUpload(factory);
          // maximum file size to be uploaded.
          upload.setSizeMax( maxFileSize );

          try{ 
          // Parse the request to get file items.
          List fileItems = upload.parseRequest(request);

          // Process the uploaded file items
          Iterator i = fileItems.iterator();

          out.println("<html>");
          out.println("<head>");
          out.println("<title>Servlet upload</title>");  
          out.println("</head>");
          out.println("<body>");
          while ( i.hasNext () ) 
          {
             FileItem fi = (FileItem)i.next();
             if ( !fi.isFormField () )  
             {
                // Get the uploaded file parameters
                String fieldName = fi.getFieldName();
                String fileName = fi.getName();
                String contentType = fi.getContentType();
                boolean isInMemory = fi.isInMemory();
                long sizeInBytes = fi.getSize();
                // Write the file
                if( fileName.lastIndexOf("\") >= 0 ){
                   file = new File( filePath + 
                   fileName.substring( fileName.lastIndexOf("\"))) ;
                }else{
                   file = new File( filePath + 
                   fileName.substring(fileName.lastIndexOf("\")+1)) ;
                }

               String path = Events.uploadFile ( fileName, "image/*", file, BUCKET );

                // fi.write( file ) ;
                out.println("Uploaded Filename: " + fileName + "<br>"+ " File Path:"+ path);
             }
          }
          out.println("</body>");
          out.println("</html>");
       }catch(Exception ex) {
           System.out.println(ex);
       }
       }
       public void doGet(HttpServletRequest request, 
                           HttpServletResponse response)
            throws ServletException, java.io.IOException {

            throw new ServletException("GET method used with " +
                    getClass( ).getName( )+": POST method required.");
       } 
    }

web.xml

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

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

fileUpload 函数将文件保存到 GCS

public static String uploadFile ( String name, String contentType, File file, String bucketName )
            throws IOException, GeneralSecurityException
    {

        InputStreamContent contentStream = new InputStreamContent ( contentType, new FileInputStream ( file ) );

        // Setting the length improves upload performance
        contentStream.setLength ( file.length () );

        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 + "/" + file.getName ();
    }

但是当我尝试用一些 API 测试客户端进行测试时，它给出了错误

org.apache.commons.fileupload.FileUploadException: the request was rejected because no multipart boundary was found

进一步将它与 Angular 中的 UI 集成并在本地测试后，我遇到了这个问题

Cross-Origin Request Blocked Reason: CORS header 'Access-Control-Allow-Origin' missing

我试图解决这个问题，但没有找到与 google appengine.

对应的解决方案

最初我试图通过此代码上传图片，但在不久的将来将使用相同的代码将 .pdf 和 .html 文件上传到 GCS。

供参考：我正在使用 Google 端点来满足我与客户端的其他数据通信需求。 Client End 是 Angular 中构建的 webapp，但它将扩展到 android 和 ios.

我们将不胜感激。

谢谢

2016 年 1 月 8 日更新

现在我正在服务器上获取文件，但我不知道在将文件发送到 Google 云存储之前我必须将文件临时保存在哪里。在

中存储文件

war\WEB-INI\

我面临的例外是

 java.security.AccessControlException: access denied ("java.io.FilePermission" "\war\WEB-INI\profile.png" "read")

Answer 1

首先你需要解决飞行前请求处理中的 CORS 问题，你需要在后端完成：在 Google App Engine 上，它通过添加 doOptions 方法完成，如：

@Override
protected void doOptions(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException 
{ 
    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");
}

那么您需要确保您发送的请求与 header 类似 Content-Type: multipart/form-data，否则您的文件将被错误编码。在 angular2 请求中，header 被设置为 post 请求中的第三个（可选）参数，例如：

let headers = new Headers();
headers.append('content-type', 'multipart/form-data');
http.post(url, body, {
                  headers:headers
                })

Answer 2

很抱歉，这并没有直接解决您的问题，但我还是想指出来。我建议使用您的常规端点之一生成临时上传 URL，您的 Angular 客户端可以使用它直接将文件发送到 Cloud Storage，而无需通过您的应用程序。一种方法是通过 blobstore API，如 here. You can upload to Cloud storage via that API as described here 所述（在同一页面的下方）。

这减少了您需要在服务器上上传的代码量，不受 GAE 请求的 32MB 限制，并且符合 Google 的建议（如上面的文档链接所示).

Answer 3

我终于可以通过 appengine 从客户端上传文件到 Google 云存储了。

我假设您在执行这些步骤之前已准备好以下内容

JSON 来自您的服务帐户的文件。
已创建默认存储桶。

第 1 步：像这样制作一个 Servlet

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." );
    }

}

第 2 步：您的存储工厂

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 ();
    }
}

第 3 步：更新您 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>

Answer 4

这里是根据docs

上传到存储的正确方法

import com.google.appengine.tools.cloudstorage.*;

public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
  String buffer = "the data to be saved in GCS bla bla";
  GcsFileOptions instance = GcsFileOptions.getDefaultInstance();
  GcsFilename fileName = new GcsFilename("bucketName", "fileName");
  GcsOutputChannel outputChannel;
  gcsService.createOrReplace(fileName, instance, ByteBuffer.wrap(buffer.getBytes()));
}

你会找到完整的代码here

Answer 5

使用com.google.cloud.storage

当运行在 appengine 上运行时 - 不需要身份验证

when 运行本地运行gcloud auth application-default login命令见 authentication

import com.google.cloud.storage.*;


public static void upload(String bucketName, String fileId, String content) throws IOException {
    Storage storage = StorageOptions.newBuilder().build().getService();

    BlobInfo fileInfo = BlobInfo.newBuilder(bucketName, fileId)
            .build();

    InputStream fileIS = IOUtils.toInputStream(content, "UTF-8");
    storage.create(fileInfo, fileIS);

}

通过 appengine 将文件上传到 Google 云存储

Upload File to Google Cloud Storage via appengine

java

google-app-engine

google-cloud-storage

google-cloud-endpoints