communicate with xml-rpc

hello everyone i want to communicate with xml-rpc in my code but i can't! and get error when i compile my code.
my code

Code:

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package com.thr.FireEagle;
import java.net.MalformedURLException;
import org.apache.xmlrpc.XmlRpcException;
import org.apache.xmlrpc.client.XmlRpcClientConfigImpl;
import java.net.URL;
import org.apache.xmlrpc.client.XmlRpcClient;
//import java.util.Vector;

public class JavaClient {
        private static Object[] params;
          public JavaClient( )
          {
              params = new Object[] { "http://dl4.mihandownload.com/2011/Alipour0c/2011.4/Welcome_MAC_World_Mihandownload.com.rar" };
          }
              public static void main( String[] args )
              {
                  System.out.println( "execute" );
                  XmlRpcClientConfigImpl config = new XmlRpcClientConfigImpl();
                  try {
                    config.setServerURL(new URL("http://127.0.0.1:6800/rpc"));
                } catch (MalformedURLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                  XmlRpcClient client = new XmlRpcClient();
                  client.setConfig(config);
                         
                  try {
                    client.execute("aria2.addUri", params );
                } catch (XmlRpcException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
               

            }

}

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i get this error when i compile my code!

Code:

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execute
org.apache.xmlrpc.XmlRpcException: URI is not provided.
        at org.apache.xmlrpc.client.XmlRpcStreamTransport.readResponse(XmlRpcStreamTransport.java:197)
        at org.apache.xmlrpc.client.XmlRpcStreamTransport.sendRequest(XmlRpcStreamTransport.java:156)
        at org.apache.xmlrpc.client.XmlRpcHttpTransport.sendRequest(XmlRpcHttpTransport.java:143)
        at org.apache.xmlrpc.client.XmlRpcSunHttpTransport.sendRequest(XmlRpcSunHttpTransport.java:69)
        at org.apache.xmlrpc.client.XmlRpcClientWorker.execute(XmlRpcClientWorker.java:56)
        at org.apache.xmlrpc.client.XmlRpcClient.execute(XmlRpcClient.java:167)
        at org.apache.xmlrpc.client.XmlRpcClient.execute(XmlRpcClient.java:137)
        at org.apache.xmlrpc.client.XmlRpcClient.execute(XmlRpcClient.java:126)
        at com.thr.FireEagle.JavaClient.main(JavaClient.java:29)

---

error occurred at line:

Code:

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client.execute("aria2.addUri", params );

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but i don't no how to fix it!
unfortunately aria2 has the method aria2.addUri but i surprised what in code i can't communicate with aria2!
please help me to fix this problem.

No everyone can help me?

If i want to create gui for aria2c you encourage me to use xml-rpc or JSON-RPC? which is better in java programming language? i can't communicate with xml-rpc in my code!
please help me to choose best approach.
tnx