Why does callback fail after uploading image to Blobstore?

Question

I am trying to upload photos to blobstore. The photo gets uploaded succesfully to blobstore but I cannot get the blobkey and servingUrl back. I tried debugging and saw that callback is not made to BlobUpload.java. It gives an error 'Connection to http:// localhost:8888 refused' I am confused because BlobUrlGet.java invokes with no problem and the photo is uploaded. I tried every type of url for the server and the servlets, none of them worked.

EDIT: I realised that if I manually change the 'localhost:8888' to '10.0.2.2:8888' in the debug mode (str variable), 'connection refused' problem goes away but this time it shows below error.

http:// localhost:8888/_ah/upload/ahFteWZpcnN0YXBwZGVtbzEyM3IiCxIVX19CbG9iVXBsb2FkU2Vzc2lvbl9fGICAgICAgN4KDAError 405 HTTP method POST is not supported by this URL

Error 405 HTTP method POST is not supported by this URL

This is the return from post method. It is the same error when I deploy to appengine and work from there.

My code is as below.

BlobUrlGet.java

public class BlobUrlGet extends HttpServlet{   
    BlobstoreService blServ = BlobstoreServiceFactory.getBlobstoreService();    
    public void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws IOException {  
        String blobUploadUrl = blServ.createUploadUrl("/blob");   
        resp.setStatus(HttpServletResponse.SC_OK);
        resp.setContentType("text/plain");    
        PrintWriter out = resp.getWriter();
        out.print(blobUploadUrl);
    }       
}

BlobUpload.java

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

    public void doPost(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();
        }

    }

Android client

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://10.0.2.2:8888/bloburl"); 
        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();
//              str = URLDecoder.decode(str, "UTF-8");
                HttpPost httppost = new HttpPost(str);
                File f = new File(picturePath);
                FileBody fileBody = new FileBody(f);
                MultipartEntityBuilder reqEntity = MultipartEntityBuilder.create();
                reqEntity.addPart("file", fileBody);
                reqEntity.addBinaryBody("Photo", f, ContentType.create("image/jpeg"), "foto2.jpg");
                httppost.setEntity(reqEntity.build());
                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 = "";
                IOUtils.copy(in, writer, encoding);
                str = writer.toString();
                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;

web.xml

  <servlet>
    <servlet-name>BlobstoreURL</servlet-name>
    <servlet-class>com.google.samplesolutions.mobileassistant.BlobUrlGet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>BlobstoreURL</servlet-name>
    <url-pattern>/bloburl</url-pattern>
  </servlet-mapping>

  <servlet>
    <servlet-name>BlobstoreUpload</servlet-name>
    <servlet-class>com.google.samplesolutions.mobileassistant.BlobUpload</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>BlobstoreUpload</servlet-name>
    <url-pattern>/blob</url-pattern>
  </servlet-mapping>

Thanks in advance.

Answer 1

doPost should have been overridden. Now it works perfectly.

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("file");
            BlobKey blobKey = blobs.get(0);