Something

package client;

import java.io.IOException;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;
import org.ksoap2.SoapEnvelope;
import org.ksoap2.serialization.SoapObject;
import org.ksoap2.serialization.SoapSerializationEnvelope;
import org.ksoap2.transport.HttpTransport;
import org.ksoap2.serialization.PropertyInfo;
import org.xmlpull.v1.XmlPullParserException;

public class SimpleClient
	extends MIDlet
	implements Runnable {
	
  private Display display;        
  private String url = "http://localhost:8080/axis/Service"; 
  TextBox textbox = null; 
    
  public void startApp() { 
	  Thread t = new Thread(this);
	  t.start();
  } 

  public void pauseApp() {} 
  public void destroyApp(boolean unconditional) {} 

  public void testWebService()
  	throws IOException {
	  
	StringBuffer stringBuffer = new StringBuffer(); 
     
	TextBox textBox = null;
	String method = "sum";
	    
	// Call the WebService
	SoapObject client = new  SoapObject(url,method);
	HttpTransport transport = new HttpTransport(url);
	    
	client.addProperty("value1",new Integer(2)); 
	client.addProperty("value2",new Integer(4));
	    
	SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
	envelope.bodyOut = client;
	envelope.addMapping("http://xml.apache.org/xml-soap","Integer",PropertyInfo.INTEGER_CLASS);
	    
	try{
		transport.call(method, envelope);
	}catch(XmlPullParserException io) {
		System.err.println(io);
	}
	    
	String result = envelope.getResponse().toString();    
	stringBuffer.append("Resultado: " + result);
	    
	// show the value on the screen.
	textBox = new TextBox("Test WebService", stringBuffer.toString(), 1024, 0); 
	display.setCurrent(textBox); 
  }
  
  public void run() {
	  display = Display.getDisplay(this); 
	  try {  
		  testWebService(); 
	  } catch (IOException ex) { 
		  System.out.println(ex);    
	  }   
  }
}

Error: Uncaught exception java/lang/RuntimeException: Cannot serialize: 2.