Spring Semester, 1999
Client-side Server, Unicast Join & Leases
© 1999, All Rights Reserved, SDSU & Roger Whitney
San Diego State University -- This page last updated 25-Mar-99
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CS 696 Emerging Technologies: Java Distributed Computing Spring Semester, 1999 Client-side Server, Unicast Join & Leases |
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© 1999, All Rights Reserved, SDSU & Roger Whitney San Diego State University -- This page last updated 25-Mar-99 |
Jini Services
Some topics we need to cover:
Server & Proxies
Note the presentation of Server Proxies follows very closely to the Simple example in Jan Newmarch’s Jini Tutorial at: http://pandonia.canberra.edu.au/java/jini/tutorial/Jini.xml. The server provides a different service in this example. A few other details relating to RMI usage and registration are also changed. It is instructive to look at both examples.
In designing a Jini service there are several different strategies:
Client-side Server
Will use an encryption server as an example
The classes:
package whitney.jini.examples.serverProxy;
public interface EncryptionInterface
{
public String[] encodeTypes();
public String encode( String encodeType, String plainText );
public String decode( String encodeType, String encodedText);
}
DirectEncryptionServer
package whitney.jini.examples.serverProxy;
import java.io.Serializable;
import sdsu.io.XorOutputStream;
import sdsu.io.XorOutputStream;
public class DirectEncryptionServer
implements EncryptionInterface, Serializable {
private static final String XOR = "xor";
private byte mask;
private String[] encodeTypes = { XOR };
public DirectEncryptionServer( byte aMask ) {
mask = aMask;
}
public String[] encodeTypes() {
return encodeTypes;
}
public String encode( String encodeType, String plainText ) {
if ( encodeType.equals( XOR) )
return xorText( plainText );
else // just an example. Save space by not using exception
return "";
}
public String decode( String encodeType, String encodedText) {
if ( encodeType.equals( XOR) )
return xorText( encodedText );
else // just an example. Save space by not using exception
return "";
}
DirectEncryptionServer
Continued
private String xorText(String text) {
byte inputBytes[] = text.getBytes();
byte[] xorBytes = new byte[inputBytes.length];
for (int k = 0; k < inputBytes.length;k++)
xorBytes[k ] =(byte) (inputBytes[k] ^ mask);
return new String(xorBytes);
}
}
DirectEncryptionClient
package whitney.jini.examples.serverProxy;
import net.jini.core.entry.Entry;
import net.jini.core.lookup.ServiceTemplate;
import net.jini.core.lookup.ServiceRegistrar;
import net.jini.core.discovery.LookupLocator;
import net.jini.lookup.entry.Name;
import java.rmi.RMISecurityManager;
public class DirectEncryptionClient{
public static void main (String[] args) throws Exception {
System.setSecurityManager (new RMISecurityManager ());
LookupLocator lookup = new LookupLocator ("jini://eli.sdsu.edu");
ServiceRegistrar registrar = lookup.getRegistrar ();
Entry[] serverAttributes = new Entry[1];
serverAttributes[0] = new Name ("EncryptionService");
ServiceTemplate template =
new ServiceTemplate (null, null, serverAttributes);
EncryptionInterface encoder =
(EncryptionInterface) registrar.lookup (template);
String testText = "Hi Mom";
String encodedText = encoder.encode( "xor", testText );
String decodedText = encoder.encode( "xor", encodedText );
System.out.println ( "Original Text: " + testText );
System.out.println ( "Encoded Text: " + encodedText );
System.out.println ( "Decoded Text: " + decodedText );
}
}
RegisterEncryptionService
package whitney.jini.examples.serverProxy;
import com.sun.jini.lease.LeaseRenewalManager;
import java.rmi.RMISecurityManager;
import java.util.Date;
import net.jini.core.discovery.LookupLocator;
import net.jini.core.entry.Entry;
import net.jini.core.lease.Lease;
import net.jini.core.lookup.ServiceID;
import net.jini.core.lookup.ServiceItem;
import net.jini.core.lookup.ServiceRegistrar;
import net.jini.core.lookup.ServiceRegistration;
import net.jini.lookup.entry.Name;
public class RegisterEncryptionService {
public static void main (String[] args) throws Exception {
System.setSecurityManager (new RMISecurityManager ());
Entry[] serverAttributes = new Entry[1];
serverAttributes[0] = new Name ("EncryptionService");
ServiceID serverID = null;
DirectEncryptionServer theServer =
new DirectEncryptionServer((byte) 11);
ServiceItem encryptServer =
new ServiceItem( serverID, theServer, serverAttributes);
LookupLocator lookup = new LookupLocator ("jini://eli.sdsu.edu");
ServiceRegistrar registrar = lookup.getRegistrar ();
ServiceRegistration serverReg =
registrar.register(encryptServer, 1000 * 60 );
System.out.println ( "Server registered" );
RegisterEncryptionService
Continued
Lease serverLease = serverReg.getLease();
LeaseRenewalManager manageLease =
new LeaseRenewalManager( serverLease, Lease.FOREVER, null );
serverID = serverReg.getServiceID();
long now = (new Date()).getTime();
long leaseDuration = (serverLease.getExpiration() - now)/1000;
System.out.println ( "Server id: " + serverID );
System.out.println ( "Server lease: " + serverLease );
System.out.println ( "Lease duration in seconds " + leaseDuration );
Thread.sleep( 1000 * 60 * 15 );
System.out.println ( "Server going down: ");
manageLease.cancel(serverLease);
}
}
RegisterEncryptionService
Explained
Set
the security manager to allow downloading of reggie code
System.setSecurityManager (new RMISecurityManager ());
Prepare
to register server with lookup service using unicast join
// Entry is used described the attributes of the service
Entry[] serverAttributes = new Entry[1];
serverAttributes[0] = new Name ("EncryptionService");
ServiceID serverID = null;
// Create the server
DirectEncryptionServer theServer =
new DirectEncryptionServer((byte) 11);
// Service items contain the data needed to register the service
ServiceItem encryptServer =
new ServiceItem( serverID, theServer, serverAttributes);
RegisterEncryptionService
Explained Continued
Perform
the unicast join
// Find the lookup service
LookupLocator lookup = new LookupLocator ("jini://eli.sdsu.edu");
ServiceRegistrar registrar = lookup.getRegistrar ();
// Register the server, the second arugment of register is the
// requested lease time
ServiceRegistration serverReg =
registrar.register(encryptServer, 1000 * 60 );
Lease serverLease = serverReg.getLease();
LeaseRenewalManager manageLease =
new LeaseRenewalManager( serverLease, Lease.FOREVER, null );
Print
out some information about the lease & server registration
serverID = serverReg.getServiceID();
long now = (new Date()).getTime();
long leaseDuration = (serverLease.getExpiration() - now)/1000;
System.out.println ( "Server id: " + serverID );
System.out.println ( "Server lease: " + serverLease );
System.out.println ( "Lease duration in seconds " + leaseDuration );
RegisterEncryptionService
Explained Continued
Keep
the server object & LeaseRenewalManager alive
Thread.sleep( 1000 * 60 * 15 );
Be
polite and cancel the lease.
System.out.println ( "Server going down: ");
manageLease.cancel(serverLease);
DirectEncryptionClient
Explained
Contact
the lookup service
LookupLocator lookup = new LookupLocator ("jini://eli.sdsu.edu");
ServiceRegistrar registrar = lookup.getRegistrar ();
Request
a DirectEncryptionServer object
Entry[] serverAttributes = new Entry[1];
serverAttributes[0] = new Name ("EncryptionService");
ServiceTemplate template =
new ServiceTemplate (null, null, serverAttributes);
EncryptionInterface encoder =
(EncryptionInterface) registrar.lookup (template);
String testText = "Hi Mom";
String encodedText = encoder.encode( "xor", testText );
String decodedText = encoder.encode( "xor", encodedText );
Running
the Example
Class
Location
Client
Machine needs:
Starting the programs
Jini components Start rmid