Mini project - 2001/2

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Mini project - 2001/2 Jini - a new computing
paradigm
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Our first jini steps basic topics 1.RMI
overview. 2.a first jini application hello
world.
rmi
rmi
rmi
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RMI-remote method invocation
provides a way for Java applications running
on different JVMs/host computers to talk to
each other.
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basic ideas/concepts 1.remote interface. 2.stubs
and skeletons - rmic.
client
server
Remote impl
Remote interface
stub
skeleton
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3.serialization. 4.parameters and return
values. 5.dynamic code loading. 6.security
implications. 7.marshaled objects. 8.the
activation framework - rmid.
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Jini basics
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3 main components 1.service 2.client 3.jini
environment - rmi,web server, lookup
service...
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service

• Device that shares its capabilities with other
  devices
• Devices Requirement
• Memory CPU
• Connection to Network
• E.g. TV, Microwave,Printer,PC,Software

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client

• A device that uses services
• Requirement
• Memory CPU
• Connection to Network
• E.g. PDA, WAP Phone, PC, Coke Machine

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The Jini environment
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How does it works? 1.create the jini
environment-lookup server online. 2.services
discover,join and register on lookup
servers. 3.clients discover and finds matching
and downloading services, then using them.
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Our first jini application - hello
world! 1.compiling running the jini
env. 2.compiling running a)server. b)client.
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Creating The jini environment 1.run a http
server (jini provides a
simple but efficient one) 2.run a rmi daemon
(exists on Java 2) 3.run a lookup server
(supplied with the reggie.jar
files in jini)
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Running the environment command lines http
server java -jar java
archive /usr/local/Java/jini1_1/lib/tools.jar
jinis http -port 8087 -dir /usr/local/Java/jini1
_1/lib the servers root
directory -verbose Rmi
daemon rmid -J-Dsun.rmi.activation.execPolicynon
e -port 1100 -log /tmp/rmid_log rmi log
directory-recvering...
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Running the environment command lines Lookup
server java -Djava.security.policy/usr/local/Ja
va/jini1_1 /example/lookup/policy.all
policy -jar /usr/local/Java/jini1_1/lib/reggie.jar
lookup service http//silver.cs.bgu.ac.il8087/re
ggie-dl.jar codebase /usr/local/Java/jini1_1/exam
ple/lookup/policy.all /tmp/reggie_log1 public
policy
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Compiling the server and client programs Compile
the server class javac -classpath
/usr/local/Java/jini1_1/lib/jini-core.jar/usr/loc
al/Java/jini1_1/lib/jini-ext.jar/usr/local/Java/j
ini1_1/lib/sun-util.jar/users/studs/bsc/2000/liyb
oviz/files/service -d /users/studs/bsc/2000/liybov
iz/files/service /users/studs/bsc/2000/liyboviz/fi
les/corejini/chapter5/HelloWorldServiceInterface.j
ava /users/studs/bsc/2000/liyboviz/files/corejini/
chapter5/HelloWorldService.java Compile the
client class javac -classpath /usr/local/Java/jin
i1_1/lib/jini-core.jar/usr/local/Java/jini1_1/lib
/jini-ext.jar/usr/local/Java/jini1_1/lib/sun-util
.jar -d /users/studs/bsc/2000/liyboviz/files/clie
nt /users/studs/bsc/2000/liyboviz/files//corejini/
chapter5/HelloWorldServiceInterface.java
/users/studs/bsc/2000/liyboviz/files/corejini/chap
ter5/HelloWorldClient.java
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Running - first the server, then the
client Server http java -jar /usr/local/Java/jin
i1_1/lib/tools.jar -port 8085 -dir
/users/studs/bsc/2000/liyboviz/files/service-dl
-verbose The Service java -cp
/usr/local/Java/jini1_1/lib/jini-core.jar/usr/loc
al/Java/jini1_1/lib/jini-ext.jar/usr/local/Java/j
ini1_1/lib/sun-util.jar/users/studs/bsc/2000/liyb
oviz/files/service -Djava.rmi.server.codebasehtt
p//silver.cs.bgu.ac.il8085/ -Djava.security.poli
cy/usr/local/Java/jini1_1/example/lookup /policy.
all corejini.chapter5.HelloWorldService
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Running then, the client The Client java -cp
/usr/local/Java/jini1_1/lib/jini-core.jar /usr/lo
cal/Java/jini1_1/lib/jini-ext.jar /usr/local/Java
/jini1_1/lib/sun-util.jar /users/studs/bsc/2000/l
iyboviz/files/client -Djava.security.policy/usr/
local/Java/jini1_1/example/lookup /policy.all
corejini.chapter5.HelloWorldClient
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Screen output

From the service gtdiscovered a lookup
service! gtset serviceID to e91bb-53434-ty7554 Fro
m the client gtGot matching service. gtIts message
is Hello, world!
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Whats behind the screen?
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The client/server known interface // This is the
interface that the service's proxy //
implements package corejini.chapter5 public
interface HelloWorldServiceInterface public
String getMessage()
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The servers code // This is the first iteration
of a Hello, World // service--it publishes a
proxy that returns // a string when asked by
clients. package corejini.chapter5 import
net.jini.discovery.DiscoveryListener import
net.jini.discovery.DiscoveryEvent import
net.jini.discovery.LookupDiscovery import
net.jini.core.lookup.ServiceItem import
net.jini.core.lookup.ServiceRegistrar import
net.jini.core.lookup.ServiceRegistration import
java.util.Hashtable import java.io.IOException i
mport java.io.Serializable import
java.rmi.RemoteException import
java.rmi.RMISecurityManager
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// This is the proxy object that will be
downloaded // by clients. It's serializable and
implements // our well-known HelloWorldServiceInte
rface. class HelloWorldServiceProxy implements
Serializable, HelloWorldServiceInterface
public HelloWorldServiceProxy()
public String getMessage() return
"Hello, world!"
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// HelloWorldService is the "wrapper" class
that // handles publishing the service
item. public class HelloWorldService implements
Runnable // 10 minute leases protected
final int LEASE_TIME 10 60 1000
protected Hashtable registrations new
Hashtable() protected ServiceItem item
protected LookupDiscovery disco // Inner
class to listen for discovery events class
Listener implements DiscoveryListener
// Called when we find a new lookup service.
public void discovered(DiscoveryEvent ev)
System.out.println("discovered a lookup
service!") ServiceRegistrar
newregs ev.getRegistrars() for
(int i0 iltnewregs.length i)
if (!registrations.containsKey(newregsi))
registerWithLookup(newregsi)

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// Called ONLY when we explicitly discard a
// lookup service, not "automatically" when a
// lookup service goes down. Once
discovered, // there is NO ongoing
communication with a // lookup service.
public void discarded(DiscoveryEvent ev)
ServiceRegistrar deadregs
ev.getRegistrars() for (int i0
iltdeadregs.length i)
registrations.remove(deadregsi) public
HelloWorldService() throws IOException
item new ServiceItem(null, createProxy(),
null) // Set a security manager
if (System.getSecurityManager() null)
System.setSecurityManager(new
RMISecurityManager()) // Search for the
"public" group, which by // convention is
named by the empty string disco new
LookupDiscovery(new String "" ) //
Install a listener. disco.addDiscoveryListen
er(new Listener())
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protected HelloWorldServiceInterface
createProxy() return new
HelloWorldServiceProxy() // This work
involves remote calls, and may take a while to
complete //Thus, since it's called from
discovered(), it will prevent us // from
responding in a timely fashion to new discovery
events. An // improvement would be to spin
off a separate short- // lived thread to do
the work. protected synchronized void
registerWithLookup(ServiceRegistrar registrar)
ServiceRegistration registration null
try registration
registrar.register(item, LEASE_TIME)
catch (RemoteException ex)
System.out.println("Couldn't register "
ex.getMessage()) return if
(item.serviceID null)
item.serviceID registration.getServiceID()
System.out.println("Set serviceID to "
item.serviceID) registrations.put(regist
rar, registration)
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// This thread does nothing but sleep, but it
// makes sure the VM doesn't exit. public
void run() while (true)
try Thread.sleep(1000000)
catch (InterruptedException ex)
// Create a new HelloWorldService
and start // its thread. public static
void main(String args) try
HelloWorldService hws new HelloWorldService()
new Thread(hws).start()
catch (IOException ex)
System.out.println("Couldn't create service "
ex.getMessage())

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The clients code
// A simple Client to exercise the
HelloWorldService package corejini.chapter5 imp
ort net.jini.discovery.DiscoveryListener import
net.jini.discovery.DiscoveryEvent import
net.jini.discovery.LookupDiscovery import
net.jini.core.lookup.ServiceRegistrar import
net.jini.core.lookup.ServiceTemplate import
java.util.Vector import java.io.IOException impo
rt java.rmi.RemoteException import
java.rmi.RMISecurityManager
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public class HelloWorldClient implements Runnable
protected ServiceTemplate template
protected LookupDiscovery disco // An
inner class to implement DiscoveryListener
class Listener implements DiscoveryListener
public void discovered(DiscoveryEvent ev)
ServiceRegistrar newregs
ev.getRegistrars() for (int i0
iltnewregs.length i)
lookForService(newregsi)
public void discarded(DiscoveryEvent
ev)
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public HelloWorldClient() throws IOException
Class types HelloWorldServiceInterface
.class template new
ServiceTemplate(null, types, null)
// Set a security manager if
(System.getSecurityManager() null)
System.setSecurityManager(new
RMISecurityManager())
// Only search the public group disco
new LookupDiscovery(new String "" )
// Install a listener
disco.addDiscoveryListener(new Listener())

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// Once we've found a new lookup service,
search // for proxies that implement //
HelloWorldServiceInterface protected Object
lookForService(ServiceRegistrar lusvc)
Object o null try o
lusvc.lookup(template) catch
(RemoteException ex)
System.err.println("Error doing lookup "
ex.getMessage()) return null
if (o null) System.err.println(
"No matching service.") return
null System.out.println("Got
a matching service.")
System.out.println("It's message is "
((HelloWorldServiceInterface)
o).getMessage()) return o
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// This thread does nothing--it simply keeps
the // VM from exiting while we do
discovery. public void run() while
(true) try
Thread.sleep(1000000) catch
(InterruptedException ex)
// Create a HelloWorldClient and start its
thread public static void main(String args)
try HelloWorldClient hwc
new HelloWorldClient() new
Thread(hwc).start() catch (IOException
ex) System.out.println("Couldn't
create client "
ex.getMessage())
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A policy file example grant // Allow
everything for now permission java.security.AllPe
rmission
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The End
To be continued...