RemoteData object creation as local object

[Pankaja Bansal]

Hi everybody

I have created an adapter class and I made this class as a remote object by extending UnicastRemoteObject . I am creating an object of this class using the code below in quotes.

DBClient localConnection = new RemoteData() ;

It works just fine but if I remove the stubs and the skeleton files, it gives an error even though I am not using the stubs functionality. My question is, Is it a violation of the below rule :

In either case, the program must allow the user to specify the location of the database, and it must also accept an indication that a local database is to be used, in which case, the networking must be bypassed entirely

Please suggest. I really need some good advice on this.

Regards
PB

[Andrew Monkhouse]

Hi Pankaja,

From memory when you instantiate a class that extends UnicastRemoteObject it exports an instance of the object using a network port (so it starts listening for a connection). A simple example of this is:

[list]Andrew Monkhouse@andrew-laptop ~[/list][list]$ cat TestUnicast.java[/list][list]import java.rmi.server.*;[/list][list] [/list][list]public class TestUnicast extends UnicastRemoteObject {[/list][list]        public static void main(String[] args) throws Exception {[/list][list]                new TestUnicast();[/list][list]        }[/list][list]<li>        public TestUnicast() throws Exception {[/list][list]                for( ; ; );[/list][list]        }[/list][list]}[/list][list] [/list][list]Andrew Monkhouse@andrew-laptop ~[/list][list]$ netstat -an | grep -c LISTEN[/list][list]39[/list][list] [/list][list]Andrew Monkhouse@andrew-laptop ~[/list][list]$ java -cp . TestUnicast &[/list][list][1] 3428[/list][list] [/list][list]Andrew Monkhouse@andrew-laptop ~[/list][list]$ netstat -an | grep -c LISTEN[/list][list]40[/list]

The program itself is in lines 3 - 14, and all it does is create an instance of a class that extends UnicastRemoteObject.

In line 16 I check how many ports I have LISTENing - this is shown in line 17 - I have 39 ports running for one reason or another :roll:

In line 20 I start my application in the background (if you are not running in a Unix (or Unix like) machine, you could simply run the additional steps in a separate DOS window).

Now that it is running, I check how many ports I have LISTENing in line 24 - in line 25 I now see that I have 40 ports LISTENing.

As for whether allowing this networking port to start listening is going to break the requirement that networking be bypassed - it is a bit of a grey area. Technically you are not using the network, so you might get away with it. But personally I would not chance it.

Regards, Andrew
[ March 13, 2006: Message edited by: Andrew Monkhouse ]

[Sergey Zolotaryov]

I avoided unexpected networking this way:
1. Created business layer object, which operates locally on the Data class
2. Created another object, which extends UnicastRemoteObject and implements the same interface that the object in 1 does. All the methods actually redirect to non-networked version of the business layer object.
3. Created a factory, which constructs either local or network business layer objects. In local mode I am guaranteed to use only non-network form. In networked form, only a network wrapper is needed (poin 2), but code is all in the non-networked version.