使用Google App Engine将文件上传到Blobstore时出现HTTP 400错误

我正在尝试使用Google App Engine Blobstore上传文件。

它应该是这样工作的：您调用BlobstoreService以获得一个上传URL，并提供一个回调URL。客户端将重定向到上载URL，发送数据，然后在完成操作后，将使用两个代表blobstore密钥的参数将其重定向到回调URL。

我们将看到，开发服务器的行为与生产服务器不同。

针对生产，我的代码可以完成上传，然后得到一个400错误响应（暗示我的请求有问题），而不是重定向回我的回调URL。如何在生产中调试？我不知道如何打开Blobstore的日志记录。

因此，我尝试在开发服务器上本地运行它。这次，如果我未设置'content-length'属性，则会得到411（未设置内容长度）。但是，如果尝试设置该属性，则会收到“ IllegalStateException：已连接”。这些例外都不会针对生产发生。

所以我不知道下一步要去哪里。我需要让它与开发人员合作，以希望可以在本地调试blobstore，或者弄清楚为什么它不能在生产环境中的blobstore上运行。

    public void upload(String uri, File file) throws IOException    {
    HttpURLConnection conn=null;
    HttpURLConnection conn2=null;
    FileInputStream fileInputStream = null;
    DataOutputStream dos=null;
    try {
        String lineEnd = "\r\n";
        String twoHyphens = "--";
        String boundary = "*****";
        int bytesRead, bytesAvailable, bufferSize;
        byte[] buffer;
        int maxBufferSize = 1 * 1024 * 1024; 
        // open a URL connection to the Servlet
        fileInputStream = new FileInputStream(file);
        URL url = new URL(uri);

        // Open a HTTP  connection to  the URL
        conn = (HttpURLConnection) url.openConnection();
        conn.setDoInput(true); // Allow Inputs
        conn.setDoOutput(true); // Allow Outputs
        conn.setUseCaches(false); // Don't use a Cached Copy
        conn.setInstanceFollowRedirects(false);
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Connection", "Keep-Alive");
        conn.setRequestProperty("ENCTYPE", "multipart/form-data");
        conn.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
//          conn.setChunkedStreamingMode(1024);
        conn.setRequestProperty("content-length", String.valueOf(file.length()));   //caused IllegalStateException "Already connected" locally, but not remotely

        log("Orignal URL: " + conn.getURL());
        //conn.connect();   //TODO duplicates url.openConnection() above?
        conn.getInputStream();  //so we can follow the redirect
        String redirectedUrl = conn.getHeaderField("Location");
        log("Redirected URL: " + redirectedUrl);
        //this is horrible and messy but let's get it working then clean it up later

        conn.disconnect();
        url = new URL(redirectedUrl);

        // Open a new HTTP  connection to  the URL
        conn2 = (HttpURLConnection) url.openConnection();
        conn2.setDoInput(true); // Allow Inputs
        conn2.setDoOutput(true); // Allow Outputs
        conn2.setUseCaches(false); // Don't use a Cached Copy
        conn2.setInstanceFollowRedirects(false);
        conn2.setRequestMethod("POST");
        conn2.setRequestProperty("Connection", "Keep-Alive");
        conn2.setRequestProperty("ENCTYPE", "multipart/form-data");
        conn2.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
        conn2.setChunkedStreamingMode(maxBufferSize);
        conn2.setRequestProperty("Content-Length", String.valueOf(file.length()));
        conn2.connect();
        dos = new DataOutputStream(conn2.getOutputStream());

        dos.writeBytes(twoHyphens + boundary + lineEnd);
        dos.writeBytes("Content-Disposition: form-data; name=\"myFile\";filename=\""+file.getName()+"\"" + lineEnd);
        dos.writeBytes(lineEnd);

        // create a buffer of  maximum size
        bytesAvailable = fileInputStream.available();

        bufferSize = Math.min(bytesAvailable, maxBufferSize);
        buffer = new byte[bufferSize];

        // read file and write it into form...
        bytesRead = fileInputStream.read(buffer, 0, bufferSize); 

        while (bytesRead > 0) {
            dos.write(buffer, 0, bufferSize);
            bytesAvailable = fileInputStream.available();
            bufferSize = Math.min(bytesAvailable, maxBufferSize);
            bytesRead = fileInputStream.read(buffer, 0, bufferSize);  
        }

        // send multipart form data necesssary after file data...
        dos.writeBytes(lineEnd);
        dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);

        // Responses from the server (code and message)
        int serverResponseCode = conn2.getResponseCode();
        String serverResponseMessage = conn2.getResponseMessage();
        //we are expecting another redirect here
        log("aaaargh! 400 instead of 302! "+serverResponseCode+" to "+conn2.getHeaderField("Location"));
    }catch (IOException e)  {
        log(e.getMessage());
        throw e;
    }catch(Exception e) {
        log(e.getMessage());
        throw new IOException(e);
    }   finally {
        //close the streams //
        if (dos!=null)  {   
            try {
                dos.flush();
                dos.close();
            }catch(IOException ioe){}
        }
        if (fileInputStream!=null)
            try {
                fileInputStream.close();
            }catch(IOException ioe){}

        if (conn!=null )
            try {
                conn.disconnect();
            }catch(Exception ioe){}

        if (conn2!=null)
            try {
                conn2.disconnect();
            }catch(Exception ioe){}

    }
}

注意，上面的serverResponseMessage字符串从生产blobstore作为“错误请求”返回