HttpTransportSE.call method returns NullPointerException frequently

Question

I connect to a webservice to download master data for my app. So, in a single download the app will need to call the webservice a no of times with different indexes.

During this, HttpTransportSE.call method returns NullPointerException for some indexes sometimes, otherwise it works fine.

My calling function is :

public String SoapAction(String[] values){

String[] data = new String[] { "CompanyID", "Username", "Password", "indexNo", "DataString","lDate" };

    SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME);

for(int i = 0; i < data.length; i++){
  PropertyInfo property = new PropertyInfo();
  property.setName(data[i]);
  property.setNamespace(NAMESPACE);
  property.setType(PropertyInfo.STRING_CLASS);
  property.setValue(values[i]); 

  request.addProperty(property);
}

SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
envelope.dotNet = true;
envelope.implicitTypes = true;
envelope.setOutputSoapObject(request);

try{
  HttpTransportSE http = new HttpTransportSE(URL);
  http.debug = true;
  System.setProperty("http.keepAlive", "false");

  http.call(SOAP_ACTION, envelope);
}catch (IOException e1) {
  e1.printStackTrace();         
  return "serverError";
} catch (XmlPullParserException e1) {
  e1.printStackTrace();
  return "serverError";     
} catch (Exception e) {
  e.printStackTrace();          
  return "serverError";
}

SoapPrimitive resultString = null;

try{
  resultString = (SoapPrimitive)envelope.getResponse();
}catch (SoapFault e) {
  e.printStackTrace();          
  return "serverError";
}

if(resultString != null){
  return resultString.toString();
} else {
  return "serverError";
}
}

I did quite a bit of googling, but couldn't find a solution

Here's the stacktrace:
02-06 14:01:14.136: W/System.err(1504): java.lang.NullPointerException

02-06 14:01:14.136: W/System.err(1504): at org.ksoap2.transport.ServiceConnectionSE.getResponseProperties(ServiceConnectionSE.java:85)

02-06 14:01:14.136: W/System.err(1504): at org.ksoap2.transport.HttpTransportSE.call(HttpTransportSE.java:167)

02-06 14:01:14.136: W/System.err(1504): at org.ksoap2.transport.HttpTransportSE.call(HttpTransportSE.java:96)

02-06 14:29:50.026: W/System.err(1504): at com.c2info.engine.WebServiceConnection.SoapAction(WebServiceConnection.java:49)

02-06 14:29:50.026: W/System.err(1504): at com.c2info.engine.DownloadData.downloadTasks(DownloadData.java:800)

02-06 14:29:50.026: W/System.err(1504): at com.c2info.engine.DownloadData$3.run(DownloadData.java:187)

Answer 1

After doing some research, I found out that it happens when the server is busy and by the time the server processes your request, the HttpTransportSE call method times out. The default time-out values in 20s. So, to overcome this, :

• Set a suitable time-out value

  HttpTransportSE http = new HttpTransportSE(URL, 30000);

• Enclose the http.call method in a while loop and retry till 'N' no of times till you get a valid response