Question

在我的Android应用程序中，我想将图像上传到Blobstore，然后检索上传网址和图像的Blobkey，这样我就可以将Blobkey存储在DataStore中。

我已尝试过此代码，但我的图片未上传：

Servlet（返回上传网址）

BlobstoreService blobstoreService = BlobstoreServiceFactory
            .getBlobstoreService();
public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {

        UploadOptions uploadOptions = UploadOptions.Builder
                .withGoogleStorageBucketName("photobucket11")
                .maxUploadSizeBytes(1048576);
        String blobUploadUrl = blobstoreService.createUploadUrl("/upload",
                uploadOptions);

        // String blobUploadUrl = blobstoreService.createUploadUrl("/uploaded");

        resp.setStatus(HttpServletResponse.SC_OK);
        resp.setContentType("text/plain");

        PrintWriter out = resp.getWriter();
        out.print(blobUploadUrl);

    }

    public void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {
        doGet(req, resp);
    }

代码：Android客户端

Bitmap bmp = BitmapFactory.decodeFile(imagePath);
                ByteArrayOutputStream out = new ByteArrayOutputStream();
                bmp.compress(CompressFormat.JPEG, 75, out);
                byte[] imgByte = out.toByteArray();
                String encodedImage = Base64.encodeToString(imgByte,
                        Base64.DEFAULT);

                HttpClient httpClient = new DefaultHttpClient();                    
                HttpGet httpGet = new HttpGet(
                        "app-url/ImgUpload");
                HttpResponse response = httpClient.execute(httpGet);
                HttpEntity urlEntity = response.getEntity();
                InputStream in = urlEntity.getContent();
                String str = "";
                while (true) {
                    int ch = in.read();
                    if (ch == -1)
                        break;
                    str += (char) ch;
                }

这将以/_ah/upload/akjdhjahdjaudshgaajsdhjsdh的形式返回上传网址，我可以用它来存储图片。

此代码使用url存储图像：

httpClient = new DefaultHttpClient();
                HttpPost postRequest = new HttpPost(str);
                ByteArrayBody bab = new ByteArrayBody(imgByte, "forest.jpg");

                MultipartEntity reqEntity = new MultipartEntity(
                        HttpMultipartMode.BROWSER_COMPATIBLE);

                reqEntity.addPart("uploaded", bab);
                reqEntity.addPart("photoCaption", new StringBody("sfsdfsdf"));
                postRequest.setEntity(reqEntity);
                response = httpClient.execute(postRequest);

                BufferedReader reader = new BufferedReader(
                        new InputStreamReader(
                                response.getEntity().getContent(), "UTF-8"));
                String sResponse;
                StringBuilder s = new StringBuilder();

                while ((sResponse = reader.readLine()) != null) {
                    s = s.append(sResponse);
                }

在这里，如果我检查字符串s的值，它会显示null。这意味着它返回一个null响应。我不知道这段代码有什么问题。请指导我解决这个问题。

Answer 1

经过多次尝试，我解决了这个问题。要在blobstore中存储图像，首先需要向servlet发出请求，这将生成上传URL：

Android客户端：它将请求生成url并从servlet获取url

HttpClient httpClient = new DefaultHttpClient();    
//This will invoke "ImgUpload servlet           
HttpGet httpGet = new HttpGet("my-app-url/ImgUpload"); 
HttpResponse response = httpClient.execute(httpGet);
HttpEntity urlEntity = response.getEntity();
InputStream in = urlEntity.getContent();
String str = "";
while (true) {
    int ch = in.read();
    if (ch == -1)
        break;
    str += (char) ch;
}

ImgUpload.java - 生成url并向客户端发送响应的Servlet

BlobstoreService blobstoreService = BlobstoreServiceFactory
            .getBlobstoreService();
public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {

//"uploaded" is another servlet which will send UploadUrl and blobkey to android client
String blobUploadUrl = blobstoreService.createUploadUrl("/uploaded"); 

        resp.setStatus(HttpServletResponse.SC_OK);
        resp.setContentType("text/plain");

        PrintWriter out = resp.getWriter();
        out.print(blobUploadUrl);
    }

在android客户端中，将下面的代码上传图像写入从上面的servlet返回的响应。

//Save image to generated url
HttpPost httppost = new HttpPost(str);
File f = new File(imagePath);
FileBody fileBody = new FileBody(f);
MultipartEntity reqEntity = new MultipartEntity();
reqEntity.addPart("file", fileBody);
httppost.setEntity(reqEntity);
response = httpClient.execute(httppost); //Here "uploaded" servlet is automatically       invoked
urlEntity = response.getEntity(); //Response will be returned by "uploaded" servlet in JSON format
in = urlEntity.getContent();
str = "";
while (true) {
    int ch = in.read();
    if (ch == -1)
        break;
    str += (char) ch;
}
JSONObject resultJson = new JSONObject(str);
String blobKey = resultJson.getString("blobKey");
String servingUrl = resultJson.getString("servingUrl");

uploaded.java- servlet返回图像的Uploadurl和Blobkey

BlobstoreService blobstoreService = BlobstoreServiceFactory
            .getBlobstoreService();

    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {
        try {
            List<BlobKey> blobs = blobstoreService.getUploads(req).get("file");
            BlobKey blobKey = blobs.get(0);

            ImagesService imagesService = ImagesServiceFactory
                    .getImagesService();
            ServingUrlOptions servingOptions = ServingUrlOptions.Builder
                    .withBlobKey(blobKey);

            String servingUrl = imagesService.getServingUrl(servingOptions);

            resp.setStatus(HttpServletResponse.SC_OK);
            resp.setContentType("application/json");

            JSONObject json = new JSONObject();

            json.put("servingUrl", servingUrl);
            json.put("blobKey", blobKey.getKeyString());

            PrintWriter out = resp.getWriter();
            out.print(json.toString());
            out.flush();
            out.close();
        } catch (JSONException e) {

            e.printStackTrace();
        }

    }

Answer 2

感谢zanky我设法理解它并且我想添加我的代码，因为在他的答案中不赞成某些代码，而且一些代码需要更多的解释，如覆盖和asynctask。顺便说一下，由于localhost和IP混淆，代码可能无法在本地服务器上运行。准备就绪后试试应用引擎。

Servlet-1 BlobUrlGet。这将是appengine方面。此servlet为客户端代码中的post方法生成上传URL。

public class BlobUrlGet extends HttpServlet{

    BlobstoreService blServ = BlobstoreServiceFactory.getBlobstoreService();

    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {

        String blobUploadUrl = blServ.createUploadUrl("/blobupload"); 

        resp.setStatus(HttpServletResponse.SC_OK);
        resp.setContentType("text/plain");

        PrintWriter out = resp.getWriter();
        out.print(blobUploadUrl);
    }

}

Servlet-2 BlobUpload当对blobstore发布帖子时，将自动调用此代码。因此，它将为我们提供blobkey和服务URL以便稍后下载图像。

public class BlobUpload extends HttpServlet {
    BlobstoreService blobstoreService = BlobstoreServiceFactory
            .getBlobstoreService();

    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {
        try {
            List<BlobKey> blobs = blobstoreService.getUploads(req).get("photo");
            BlobKey blobKey = blobs.get(0);

            ImagesService imagesService = ImagesServiceFactory.getImagesService();
            ServingUrlOptions servingOptions = ServingUrlOptions.Builder.withBlobKey(blobKey);

            String servingUrl = imagesService.getServingUrl(servingOptions);

            resp.setStatus(HttpServletResponse.SC_OK);
            resp.setContentType("application/json");

            JSONObject json = new JSONObject();

            json.put("servingUrl", servingUrl);
            json.put("blobKey", blobKey.getKeyString());

            PrintWriter out = resp.getWriter();
            out.print(json.toString());
            out.flush();
            out.close();
        } catch (JSONException e) {

            e.printStackTrace();
        }

    }
}

Android客户端代码。这个asynctask将调用servlet并使用它获得的信息向blobstore发布帖子。

    private class GetBlobUrlTask extends AsyncTask<Void, Void, Void> {

        @Override
        protected Void doInBackground(Void... arg0){  

        HttpClient httpClient = new DefaultHttpClient();    
        //This will invoke "ImgUpload servlet           
        HttpGet httpGet = new HttpGet("http://PUT_YOUR_URL_HERE/bloburlget"); 
        HttpResponse response;
        try {
            response = httpClient.execute(httpGet);         
            HttpEntity urlEntity = response.getEntity();
            InputStream in = urlEntity.getContent();
            String str = ""; 
            StringWriter writer = new StringWriter();
            String encoding = "UTF-8";
            IOUtils.copy(in, writer, encoding);
            str = writer.toString();
                HttpPost httppost = new HttpPost(str);
                File f = new File(picturePath);
                MultipartEntityBuilder reqEntity = MultipartEntityBuilder.create();
                reqEntity.addBinaryBody("photo", f, ContentType.create("image/jpeg"), "foto2.jpg");
                httppost.setEntity(reqEntity.build());
                response = httpClient.execute(httppost); //Here "uploaded" servlet is automatically       invoked
                str = EntityUtils.toString(response.getEntity());
                JSONObject resultJson = new JSONObject(str);
                blobKey = resultJson.getString("blobKey");
                servingUrl = resultJson.getString("servingUrl");

        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return null;

    }
    }

毕竟我们需要更新web.xml才能执行servlet。

  <servlet>
    <servlet-name>BlobUrlGet</servlet-name>
    <servlet-class>PUT_YOUR_PACKAGE_NAME.BlobUrlGet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>BlobUrlGet</servlet-name>
    <url-pattern>/bloburlget</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>BlobUpload</servlet-name>
    <servlet-class>PUT_YOUR_PACKAGE_NAME.BlobUpload</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>BlobUpload</servlet-name>
    <url-pattern>/blobupload</url-pattern>
  </servlet-mapping>

Answer 3

我在Android Studio中使用端点，感谢SAVANTE，我可以完成我的代码，但我不得不进行小幅调整。

Servlet 1中的

：我使用了端点，我可以在我的方法中轻松处理OAuth2：

@ApiMethod(name = "getBlobURL",  scopes = {Constants.EMAIL_SCOPE},
            clientIds = {Constants.WEB_CLIENT_ID,
                    Constants.ANDROID_CLIENT_ID,
                    com.google.api.server.spi.Constant.API_EXPLORER_CLIENT_ID},
            audiences = {Constants.ANDROID_AUDIENCE})
    public BlobAttributes getBlobURL(User user) throws  UnauthorizedException, 
     ConflictException{

        //If if is not null, then check if it exists. If yes, throw an Exception
        //that it is already present
        if (user == null){
            throw new UnauthorizedException("User is Not Valid");
        }

        BlobstoreService blobstoreService = BlobstoreServiceFactory.getBlobstoreService();
        String blobUploadUrl = blobstoreService.createUploadUrl("/blobupload");

        //BlobAttributes is a class 
        BlobAttributes ba= new BlobAttributes();
        ba.setBlobURL(blobUploadUrl);
        return ba;
    }

我的后端在Android Studio的端点，不要让我使用JSONObject为这个rason我自己制作Json：在Servlet 2中：

String myJson = "{'servingUrl': '" + servingUrl +
                        "', 'blobKey': '" + blobKey.getKeyString() + "'}";

            PrintWriter out = resp.getWriter();
            out.print(myJson);
            out.flush();
            out.close();

我希望为其他人工作，我花了48个小时试图了解并操作Blobstore。

修改：

要从客户端进行经过身份验证的呼叫，这是使用Google凭据的方式：

accountName = settings.getString(start.KEY_ACCOUNT_NAME, null); //Email account that you before save it
            credential = GoogleAccountCredential.usingAudience(getActivity(),
                    start.WEB_CLIENT_ID); //WEB_CLIENT_ID is your WEB ID in Google Console
            credential.setSelectedAccountName(accountName);

构建您的Endpoint时，请填写您的凭证：

PostEndpoint.Builder builder = new PostEndpoint.Builder(AndroidHttp.newCompatibleTransport(), new AndroidJsonFactory(), credential)
                        .setRootUrl(getActivity().getString(R.string.backend_url_connection));
                myApiService = builder.build();

要获取客户端的帐户名称，请使用Plus API

accountName = Plus.AccountApi.getAccountName(mGoogleApiClient);

阅读评论中的链接，使用Google文档可以很好地理解这一点。

从Android客户端将图像存储到Blobstore并检索blobkey并上传URL以存储在Datastore中。 - GAE

3 个答案: