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。 - 盖伊

Posted 2023-02-24

【中文标题】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。 - 盖伊

【英文标题】：Store image to Blobstore from android client and retrieve blobkey and upload url to store in Datastore. - GAE

【发布时间】：2014-04-05 19:25:51

【问题描述】：

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

我试过这段代码，但我的图片没有上传：

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：安卓客户端

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，我可以使用它来存储图像。

这段代码使用url来存储图片：

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);
                

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空响应。我不知道这段代码有什么问题。请指导我解决这个问题。

【参考方案1】：

经过多次尝试，我解决了这个问题。要将图像存储在 blobstore 中，首先 android 需要向 servlet 发出请求，servlet 将生成上传 url：

Android客户端：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 - Servlet 生成 url 并向客户端发送响应

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，编写下面的代码上传图片到上面的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 返回图片的 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();
        

    

【讨论】：

我写的代码和你完全一样，但我的 path_success 从来没有被调用过。我认为这不是调用，因为当我在我的 android 代码中创建文件时： File f = new File(uri.getpath());这个文件 f 的长度为 0，所以我什么都不发送。你知道我为什么会有这种行为吗？

path_success 是什么？你在上传之前保存文件吗？

在uploaded.java-servlet 中，你从哪里得到JSONObject 类？从哪里进口的？

@tschakkkiiiii JSONObject 是从 com.google.appengine.labs.repackaged.org.json.JSONObject 导入的

@zankythanx 的答案，它帮助分配。只是为了确保“my-app-url”类似于 myAppIdName.appspot.com，对吗？ myAppName 是 link 的 appEngine 项目的名称？

【参考方案2】：

感谢 zanky，我设法理解了它，我想添加我的代码，因为在他的答案中不推荐使用某些代码，并且某些代码需要更多解释，例如覆盖和异步任务。顺便说一句，由于本地主机和 IP 混淆，代码可能无法在本地服务器上运行。准备好后尝试应用引擎。

Servlet-1 BlobUrlGet。这将转到 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 当发布到 blobstore 时，将自动调用此代码。结果，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发布到 blobstore。

    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>

【讨论】：

你知道在这个例子中让 MultipartEntityBuilder 和 ContentType 工作需要什么 gradle 编译命令吗？我似乎在使用 apache mime 版本时遇到了很多麻烦

【参考方案3】：

我正在使用 Android Studio 中的端点，感谢 SAVANTE，我可以完成我的代码，但我必须进行一些小的调整。

在 Servlet 1 中： 我使用了 Endpoints，这样我可以在我的方法中非常轻松地处理 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;
    

我在端点 Android Studio 中的后端，不要让我为此使用 JSONObject 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();

我希望对其他人有用，我花了 48 小时试图了解和操作 Blobstore。

编辑：

对于来自客户端的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);

在构建您的端点时放置您的凭据：

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 cmets 中的链接，并使用 Google 文档更好地理解这一点。

【讨论】：

嘿 Carlos，你能编辑或添加 servlet 1 的完整代码吗？这对我有很大帮助。使用 oauth 调用 servlet 1 的方法也很棒。

嗨 Savante，您是否从一开始就对如何使用 OAuth2 感兴趣？您是否在 Android Studio 中使用 Endpoints？

我使用的是 Eclipse，但现在我正在尝试了解 Android Studio，因为 Google 建议采用这种方式。我不会拒绝任何信息。 :)

这里有很多主题，与本文的问题无关。那我就给你我照做的认证教程：cloud.google.com/appengine/docs/java/endpoints/auth

现在来自客户端的经过身份验证的调用：cloud.google.com/appengine/docs/java/endpoints/…