title: Why "form POST" stay in status "PENDING" when trying to uplaod image to blobstore
body: <p>When I go to <a href="https://appengine.google.com/blobstore/" rel="nofollow">https://appengine.google.com/blobstore/</a> I see that images are uploaded (cf. blob viewer).</p>
  
  <p>In prod mode : </p>
  
  <p>In chrome dev tool, when I submit the form in order to upload the image, I see that the form stay in a "<strong>PENDING</strong>" status. The purpose of this mail is to help me to understand what should fail. In the Network tab, I hae the following Header : </p>
  
  <p>Request</p>
  
  <pre><code>URL:http://www.mananaseguro.com/_ah/upload/AMmfu6aImWsEdAeiy_FVrscqQiRoRSvjK2QSX6thgKTaMk4nKLbiJg86RrocrzAqWj2X2vi1gKrY_Yvr2kSQNpFMwxBiUFa1Tk5oEVZGjhMm_9SavhOAjNoteylbfLT7aZ5dUYMaDR2N/ALBNUaYAAAAAUeJL86BP_9txQLF54r96AvYfm1Nuw90l/
  Request Headersview source
  Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
  Content-Type:multipart/form-data; boundary=----WebKitFormBoundarymTEOMdBbtHBxoFJb
  Origin:http://www.mananaseguro.com
  Referer:http://www.mananaseguro.com/
  User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.72 Safari/537.36
  Request Payload
  ------WebKitFormBoundarymTEOMdBbtHBxoFJb
  Content-Disposition: form-data; name="myFile"; filename="trailer-8.webp"
  Content-Type: image/webp
  ------WebKitFormBoundarymTEOMdBbtHBxoFJb--
  </code></pre>
  
  <p>And in the response tab :</p>
  
  <pre><code>**This request has no data response**
  </code></pre>
  
  <p>I have done the following servlet configuration (GUICE)
          serve("/_ah/upload").with(BlobstoreUploadFinishedServlet.class); // post
          serve("/_ah/serve").with(Servlet_Serve.class);</p>
  
  <p>And some related line of code I call :</p>
  
  <p>resp.sendRedirect("/_ah/serve?blob-key=" + url);</p>
  
  <p>String url = blobstoreService.createUploadUrl("/_ah/upload"); </p>
  
  <p>Question : Can you explain me why "I" do not have a response (form POST is always pending) ?
  I also do not know if I should use "/_ah/" or not (I have decided to put it everywhere) ?</p>
  
  <hr>
  
  <p>I have another issue in dev mode, I cannot test upload to blobstore, because I have the following error : </p>
  
  <p>WARNING: /_ah/upload/ag1tYW5hbmFzZWd1cm8xch0LEhVfX0Jsb2JVcGxvYWRTZXNzaW9uX18Y2aQCDA
  java.lang.NullPointerException
      at com.google.appengine.api.blobstore.dev.UploadBlobServlet.getSessionId(UploadBlobServlet.java:134)</p>
  
  <p>Question : What is happening ? Is it a problem related to cookies ?</p>
  
  <p>Thanks you,</p>