Question

I have a ASP.Net web api which is intended to send a new file over the internet encoded as Base64. To do so, I have a public exposed REST service:

    string imei = ControllerContext.Request.Headers.GetValues("IMEI").FirstOrDefault();
    byte[] FileAsBytes = null;
    String base64 = null;
    var svcs = new CrudService.CrudServiceClient();

    if (svcs.IsDeviceAccepted(imei))
    {
        FileAsBytes = svcs.DownloadSoftwareVersion();
    }

    if(FileAsBytes != null)
    {
         base64 = Convert.ToBase64String(FileAsBytes);
    }

    return base64;

and a Private service, CRUD service, which communicates directly with the database and the core layers.

After some debugging I found out that this service returns the correct lenght, something like 4194304 bytes, which seems to correspond to the size of file. However on the client side, I am contacting this service inside a AsyncTask:

    @Override
    protected String doInBackground(String... params) {
        Log.i("UpdateManager: ", "Inside doInBackground");

        try {

            String imei = params[0];
            String urlString = "http://10.118.18.50/Mobile.RESTPublicService/api/SoftwareUpdate";

            HttpPost post = new HttpPost(urlString);
            post.addHeader("IMEI", imei);
            response = httpClient.execute(post);

            Log.w("Update-Response: ",
                    Integer.toString(response.getStatusLine().getStatusCode())
                            + " " + response.getStatusLine());

            if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {

                is = response.getEntity().getContent();
                IOUtils.copy(is, writer, "UTF-8");

                _log.debug(writer.toString());

                Log.w("CONTENT: ", writer.toString());
                byte[] result = new byte[MAX_FILE_SIZE]; //7242880 b
                result = decodeBase64(writer.toString());

                Log.w("BYTE ARRAY LENGTH: ", Integer.toString(result.length));

            }

        } catch (ClientProtocolException e) {
            Log.e("Client: ", e.getMessage());
            _log.error(e.getMessage());
            return FAILED_DUE_TO_EXCEPTION;
        } catch (IOException e) {
            Log.e("IO: ", e.getMessage());
            _log.error(e.getMessage());
            return FAILED_DUE_TO_EXCEPTION;
        }
        return response.getStatusLine().toString();
    }

The interesting point here is the result = decodeBase64(writer.toString()); and the decodeBase64 method:

protected byte[] decodeBase64(String s) {
        return Base64.decode(s);
    }

The String s is what I get from the webservice:

UEsDBBQACAgIAJteK0IAAAAAAAAAAAAAAAAZAAQAcmVzL2FuaW0vYWN0aXZpdHlmYWRlLnhtbP7KAABdkN9OwjAchc+PbW4YErnwgkRuuSGEek1MDI/SsMkmbF26es8D+AA+hs+hD6Wn0GXKab60/fq/ETK8CyCY4xNgL4TuCUPuyANZkEeyIXvySiaTqnGFbc1RO2MxHr9YU2+PbamRps5cWlmWv1ntKtNQ6ia3psqxXJbOtRul

This is not the whole file, but I can see that this is base64 encoded

When this string is passed inti the decodeBase64 method I only get this error message:

Then the application terminates. Is this the way to handle Base64 String? Can someone suggest how I can create a file from this base64 string? My first thought was to convert it to a byte array, and then create a file.

Answer 1

Looks to me like you’ve got a quoted string there – because " is what seems to be making it blow up. Is the web service returning a JSON string? If it is, then it will be surrounded by quotes and you have to take those off in order to parse it from base 64.