Data Interface definition for server and client

[Gokul Krishnan]

Hi Everyone,
I am currently doing the FBN assignment and have a question regarding the
Definition of the Interface for the Database server and Data client.
I have put all the public methods in the data class in an interface which
can be used by the client and server.
I currently have the 2 following interface definitions for data client
and the RMI server (as given below).I would like to know if this approach
is acceptable as per good OOP design principles ? The reason for the separation
is exception handling :

 
// This interface will be implemented by the RMI Server
public interface DataBaseServerIF extends Remote
{
    public FieldInfo [] getFieldInfo() throws RemoteException; 
    public int getRecordCount() throws RemoteException;
    public void unlock(int record) throws RemoteException;
    public void lock(int record) throws RemoteException;
    public DataInfo[] criteriaFind(String criteria) throws RemoteException;
    ...
    ...
    ...
}  
// This interface will be implemented by the data client
public interface DataClientIF 
{
    public FieldInfo [] getFieldInfo() ; 
    public int getRecordCount();
    public void unlock(int record);
    public void lock(int record) throws IOException;
    public DataInfo[] criteriaFind(String criteria) throws DatabaseException;
    ...
    ...
    ...
}

The reason I chose this approach is this : If one interface extends another,
then the exception handling gets mucked up(one method does not throw an
exception in the local mode while in the server it must throw an exception
For e.g. the method getFieldInfo()
This way it is cleaner. But if a method is added to the the Data class, it
has to be updated in 2 interfaces separately(the only drawback I see).
Any comments/suggestions on this design ?
Thanks
Gokul

[Andrew Monkhouse]

Hi Gokul
That is the same approach I took.
I also had the same concerns as you - that a change to Data that has to be propogated would require both interfaces to be changed - but I could not see a clean way around it.
Regards, Andrew

[Xiao Qinglai]

Given that we have:
A interface DataInterface resides in suncertify.db;
A interface RemoteData, which extends Remote, resides in suncertify.server;
Now we have a package named suncertify.client, in which package, we want to dynamicly change data's resource: either from local or from network.
We can write a class ClientData implements suncertify.db.DataInterface. ClientData works like a wrapper of RemoteData, that is, use try--catch to hide RemoteException.
Now, given we have suncertify.client.Client, we can set Client's data like this:

public void setData(DataInterface dataIf) {
    this.data = dataIf;
}

In this way, we can dynamicly change DataInterface in Client.
In one word, the point is to create a class (ClientData) to implement DataInterface, and to wrap RemoteData (that is, catch RemoteException in method, instead of throwing it).
[ July 16, 2003: Message edited by: Xiao Qinglai ]
[ July 16, 2003: Message edited by: Xiao Qinglai ]