RMI Interface

[Pete Palmer]

Hi

The code below is my current approach to provide an RMI interface to the client.

    
public interface DBAccess {
	public String[] readRecord(long recNo) throws RecordNotFoundException;

	public void updateRecord(long recNo, String[] data, long lockCookie)
			throws RecordNotFoundException, SecurityException;

	public void deleteRecord(long recNo, long lockCookie)
			throws RecordNotFoundException, SecurityException;

	public long[] findByCriteria(String[] criteria);

	public long createRecord(String[] data) throws DuplicateKeyException;

	public long lockRecord(long recNo) throws RecordNotFoundException;

	public void unlock(long recNo, long cookie) throws SecurityException;
}



public interface  ClientDBAcess extends DBAccess {

	/**
	 * Return the record detail held by the specified recNo
	 * in the database.
	 * This interface is ideal for reading a record as the detail is
	 * returned in a serialised object.
	 */
	public Record readRecordObj (long recNo) throws RecordNotFoundException;
	
	/**
	 * Return all the records stored in the database
	 */
    public List<Record> readRecords()throws IOException;
    
}



public interface DatabaseRemote extends Remote, ClientDBAcess {
}


public class DatabaseRemoteImpl extends UnicastRemoteObject
implements DatabaseRemote   {

    //
    // Data class also implements ClientDBAcess.
    private Data database;

	public long[] findByCriteria(Record criteria) throws RemoteExceptions {
		return database.findByCriteria(criteria.toStringArray());
	}

	public long lockRecord(long recNo) throws RecordNotFoundException, RemoteExceptions {
		return database.lockRecord(recNo);
	}

	public Record readRecord(long recNo) throws RecordNotFoundException, RemoteExceptions {
		
		return database.readRecordObj(recNo);		
	}
	
    public List<Record> readRecords() throws IOException, RemoteExceptions {
    	return database.readRecords();    	   	
    }
}

My thoughts on this approach.

DBAccess is Sun’s provided interface.

ClientDBAcess extends above to introduce two additional methods –

readRecordObj() – identical to Sun’s readRecord() except a Record object is returned instead
of an Array of Strings. I don’t particularly like the method name !
readRecords() – Return all records in the database. Useful to initialise the JTable on startup.


1) The client will communicate with either the local or remote database via a ClientDBAcess instance.
In the local mode, I will return an instance of Data, which implements ClientDBAcess.
In the remote mode, I will return an instance of DatabaseRemote, which implements ClientDBAcess.
This way, the client will not have to worry whether the connection is remote or local.
Any issues that I have overlooked/should consider with this approach ?

2) Is it OK to simply add the RemoteExceptions to the methods DatabaseRemoteImpl class, like I have shown.

3) My client will not be using the readRecord() which returns an array of Strings or findByCriteria() which
returns a array of londs, however, if the client did use either, would there be any issue with serialization ?

4) Do I need to consider any serialization issue with respect List<Record> readRecords() ?


Pete

[Alecsandru Cocarla]

1. See 2.
2. It's not possible, your remote class won't compile.
3. No.
4. Only that Record is Serializable.

[Roel De Nijs]

Hi Pete,

Because i had also no experience with RMI i made a small testing application to see how RMI works and what you can do and can not do regarding your interface and the RemoteException.

You can find this thread here.

Regards,
Roel