Hi there, I use dbus-java to communicate via DBus. This works fine as long as I stick to primitve types natively supported by the java dbus lib such as String, int, boolean and so on. However I try to send objects instances (of a class called Metadata) via DBus, which have a String member and a ArrayList<String> member. So I implemented the serialize and deserialize methods according to the API and the tutorial which ships with the lib.  When trying to call a remote method which should deliver a Metadata object, I receive the following exception: Exception in thread "main" org.freedesktop.dbus.exceptions<div id="mb_0">.DBusExecutionException: Wrong return type (not expecting Tuple)     at org.freedesktop.dbus.RemoteInvocationHandler.convertRV(RemoteInvocationHandler.java:65)     at org.freedesktop.dbus.RemoteInvocationHandler.executeRemoteMethod(RemoteInvocationHandler.java:138)     at org.freedesktop.dbus.RemoteInvocationHandler.invoke(RemoteInvocationHandler.java:187)     at $Proxy1.pongMD(Unknown Source)     at de.ichaus.entw.DBusTest.dBusClient.DBusClient.main(DBusClient.java:65) I put together a small testcase existing of a server and a client in case anyone want to run it. I thought it might be a problem with that List member in Metadata. Won't work with Vector<String>, ArrayList<String> or Collection<String> either. I tried both versions Version 2.4 and 1.13 of the library. It would be great if anyone could suggest something I am missing out on or got wrong. :) Greetings Johannes Felten CLASSES: //------------------------------------------------------------------------------------------------------------------ package de.ichaus.entw.DBusTest.dBusServer; import java.io.IOException; import org.freedesktop.dbus.DBusConnection; import org.freedesktop.dbus.exceptions.DBusException; public class DBusServer{     private static DBusConnection conn = null;     private static Pong pongObj = null;     private static void connect(){         try {             conn = DBusConnection.getConnection(DBusConnection.SESSION);             conn.requestBusName("de.ichaus.entw.DBusServerPingPong");             conn.exportObject("/pongObj",pongObj);         } catch (DBusException e) {             e.printStackTrace();         }     }     /**      * @param args      */     public static void main(String[] args) {         pongObj = new Pong();         connect();         System.out.print("Press ENTER to exit.");         try {             System.in.read();         } catch (IOException e) {             // TODO Auto-generated catch block             e.printStackTrace();         }         finally{             conn.disconnect();         }     } } //------------------------------------------------------------------------------------------------------------------ package de.ichaus.entw.DBusTest.dBusServer; import java.util.ArrayList; import org.freedesktop.dbus.DBusInterface; import org.freedesktop.dbus.Tuple; import de.ichaus.entw.DBusTest.types.Metadata; public class Pong implements DBusConnectorInterface {     private Metadata pongMD;     public Pong(){};     public String pong() {         return "pong";     }     public void makeMD(String mdStr){         ArrayList<String> strLst = new ArrayList<String>(3);         for (int i=0; i<3; i++)             strLst.add(mdStr+"_"+i);         pongMD = new Metadata(mdStr, strLst);     }     public Metadata pongMD(){         return pongMD;     }     public boolean isRemote() {         return false;     } } //------------------------------------------------------------------------------------------------------------------ package de.ichaus.entw.DBusTest.dBusClient; import java.util.Calendar; import org.freedesktop.dbus.DBusConnection; import org.freedesktop.dbus.exceptions.DBusException; import de.ichaus.entw.DBusTest.dBusServer.DBusConnectorInterface; import de.ichaus.entw.DBusTest.dBusServer.Pong; public class DBusClient {     private static DBusConnection conn = null;     private static DBusConnectorInterface pongObj = null;     private static void connect(){         try {             conn = DBusConnection.getConnection(DBusConnection.SESSION);             //pongObj = (DBusConnectorInterface)conn.getRemoteObject("de.ichaus.entw.DBusServerPingPong", "/pongObj");             //pongObj = (DBusConnectorInterface)conn.getRemoteObject("de.ichaus.entw.DBusServerPingPong", "/pongObj", de.ichaus.entw.DBusTest.dBusServer.DBusConnectorInterface.class);             pongObj = (DBusConnectorInterface)conn.getRemoteObject("de.ichaus.entw.DBusServerPingPong", "/pongObj", DBusConnectorInterface.class);         } catch (DBusException e) {             // TODO Auto-generated catch block             e.printStackTrace();         }     }     private static String getTimeStamp(){         Calendar rightNow = Calendar.getInstance();         return rightNow.get(Calendar.YEAR) + "-"                 + (rightNow.get(Calendar.MONTH) + 1) + "-"                 + rightNow.get(Calendar.DAY_OF_MONTH) + " "                 + rightNow.get(Calendar.HOUR_OF_DAY) + ":"                 + rightNow.get(Calendar.MINUTE) + ":"                 + rightNow.get(Calendar.SECOND) + "."                 + rightNow.get(Calendar.MILLISECOND);     }     /**      * @param args      */     public static void main(String[] args) {         System.out.println("Starttime:    " + getTimeStamp());         connect();         System.out.println("Connected:    " + getTimeStamp());         System.out.println("\n Play some ping pong...");         for (int i = 0; i < 10; i++) {             System.out.println("I said ping...");             if (pongObj != null)                 System.out.println("Server said " + pongObj.pong());             else                 System.out.println("Server said nothing...");         }         System.out.println("Endtime:      " + getTimeStamp());         System.out.println(" Finished ping pong play.");         System.out.println("\nPlay some Metadata ping pong...");         for (int i = 0; i < 10; i++) {             System.out.println("I said makeMD...");             if (pongObj != null)             {                 pongObj.makeMD("pong_"+i);                 System.out.println("Server said " + pongObj.pongMD());             }             else                 System.out.println("Server said nothing...");         }         System.out.println(" Finished Metadata ping pong.");         if (conn != null)             conn.disconnect();         System.out.println("Disconnected: " + getTimeStamp());     } } //------------------------------------------------------------------------------------------------------------------ package de.ichaus.entw.DBusTest.dBusServer; import org.freedesktop.dbus.DBusInterface; import de.ichaus.entw.DBusTest.types.Metadata; public interface DBusConnectorInterface extends DBusInterface {     public String pong();     public void makeMD(String mdStr);     public Metadata pongMD(); } //------------------------------------------------------------------------------------------------------------------ package de.ichaus.entw.DBusTest.types; import java.util.ArrayList; import java.util.List; import org.freedesktop.dbus.DBusSerializable; import org.freedesktop.dbus.Position; import org.freedesktop.dbus.exceptions.DBusException; public class Metadata implements DBusSerializable{     @Position(0)     private String md5Sum = "";     @Position(1)     private List<String> someStrings;     public Metadata(){}     public Metadata(String md5, List<String> strings){         md5Sum = md5;         someStrings = strings;     }     public Object[] serialize() throws DBusException {         return new Object[] {this.md5Sum, this.someStrings};     }     public void deserialize(String md5sum, List<String> someStrings){         this.md5Sum = md5sum;         this.someStrings = new ArrayList<String>(someStrings);     } } //------------------------------------------------------------------------------------------------------------------</div>