Java Reference
In-Depth Information
We now have a unique instance of the
DvdDatabaseImpl
class for each connected client. If
each
DvdDatabaseImpl
has its own instance of
DvdDatabase
, then the instance of
DvdDatabase
can be used to identify the client to the
ReservationManager
.
Since using a factory will work for both a socket solution and an RMI solution, and since
we are building
both
socket connectivity and RMI connectivity in this topic, we will present
the
ReservationManager
code as though a factory solution is being used.
Let's demonstrate the use of a factory and compare it to a nonfactory scenario. Included
in the downloaded code are two classes,
RmiFactoryExample.java
and
RmiNoFactoryExample.
java
. As you can probably surmise from the names, one class serves as a factory implementa-
tion test case, while the other serves as a test case for a nonfactory implementation. The
RmiFactoryExample
class demonstrates how multiple instances of the
DvdDatabase
is instanti-
ated, and the
RmiNoFactoryExample
class demonstrates how multiple requests result in reuse
of our
DvdDatabase
instance.
Both sample programs extend
Thread
and implement the
run
method. The
main
in each
sample test program also spawns two threads to simulate a multiuser environment. The only
difference between the two test programs involves which remote object gets registered. The
RmiNoFactoryExample
registers a
DvdDatabase
remote object, while the
RmiFactoryExample
reg-
isters the
DvdDatabaseFactory
remote object. Correspondingly, the
run
methods must cast the
appropriate remote interface returned from the
lookup
method. Refer to Listings 6-5 and 6-6.
Listing 6-5.
The Main Method in the RmiNoFactoryExample Class
public static void main(String[] args) throws Exception {
LocateRegistry.createRegistry(1099);
Naming.rebind("RmiNoFactoryExample", new DvdDatabaseImpl());
Thread a = new RmiNoFactoryExample("A");
a.start();
Thread.sleep(1000);
Thread b = new RmiNoFactoryExample("B");
b.start();
a.join();
b.join();
System.exit(0);
}
public void run() {
try {
System.out.println("getting a remote handle to a DvdDatabase."
+ this.hashCode());
DvdDatabaseRemote remote
= (DvdDatabaseRemote)Naming.lookup("RmiNoFactoryExample");
}
catch (Exception e) {
System.err.println(e);
e.printStackTrace();
}
}
