RMI UnmarshalException Occurs after some time

Question

Hi,
I have a client server application that talks via rmi. My client saves data to a server or gets data by passing in parameters that include string, boolean and a Hashtable. The data is saved and retrieved many times. However, after some time, the RMI can't even find the method. That is, the client calls a method and I get a unmarshalling exception from the client, basically stating that it can't find the method.
Here is the method in my interface, the method in question is the override method, the getLast works fine all the time:
public interface Admin extends Remote
     Hashtable getLast(Hashtable setLashtHash) throws RemoteException;
//override method can query or set a new data in the form of a hashtable. It return a Hashtable or null
     Object override(boolean setNew, String ticker, boolean getOverrideHash,boolean getLast, boolean getPrevious,Hashtable newOverride) throws RemoteException;
Here's the implementation of override:
     synchronized public Object override(boolean setNew, String ticker, boolean getOverrideHash,boolean getLast, boolean getPrevious,Hashtable newOverride) throws RemoteException
          try{
          if(setNew)
               if(newOverride!=null)
               System.out.println("Saving override hash, entries=" + newOverride.size());
               overrideHash=newOverride;
          else if(getOverrideHash)
               if(overrideHash!=null)
               System.out.println("Getting override hash entries=" + overrideHash.size());
               return overrideHash;
          else
               if(getLast)
                    if(overrideHash==null)
                         System.out.println("override hash is null");
                         return null;
                    OverrideStruct os=(OverrideStruct)overrideHash.get(ticker);
                    if(os.last!=null)
                         System.out.println("Last price for ticker " + ticker + " is=" +os.last);
                         Float last=os.last;
                         return last;
                    return null;
               else if(getPrevious)
                    if(overrideHash==null)
                         return null;
                    OverrideStruct os=(OverrideStruct)overrideHash.get(ticker);
                    if(os.previous!=null)
                         Float previous=os.previous;
                         return previous;
                    return null;
     }catch(Exception e)
          System.out.println("Unknown Exception caught in override function");
          e.printStackTrace();
          return null;
Here is the exception, please help.
java.rmi.ServerException: RemoteException occurred in server thread; nested exce
ption is:
java.rmi.UnmarshalException: invalid method hash
java.rmi.UnmarshalException: invalid method hash
at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknow
n Source)
at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
at sun.rmi.server.UnicastRef.invoke(Unknown Source)
at AdminImpl_Stub.override(Unknown Source)
at StocksTable$12.run(stockstable.java:481)
Please help,
Thanks Steve

Answer 1

By the way, this is how my server calls the client:
Hashtable otable=(Hashtable)a1.override(false,new String(""),true,false,false,new Hashtable());