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1 1 of 10 11/13/2007 7:35 AM CS 696 Emerging Technologies: Java Distributed Computing Spring Semester, 1999 Simple Jini Example Previous Lecture Notes Index Next 1999, All Rights Reserved, SDSU & Roger Whitney San Diego State University -- This page last updated 18-Mar-99 References Hello World Example Example Explained The Client Service Lookup Matching Entries Standard Entry Subclasses Entry & JavaBeans HelloServer Contents of Doc 18, Simple Jini Example References Jini API, Local on-line version at: Jini Entry Specification 1.0 January 25, 1999 Jini Entry Utilities Specification 1.0 January 25, 1999 Jini Lookup Service Specification 1.0 January 25, 1999 Jini Lookup Attribute Schema Specification 1.0 January 25, 1999 These documents are available at: Noel Enete s Nuggets for Jini, Hello World Example Doc 18, Simple Jini Example Slide # 2 This example: Uses a null lease Uses unicast discovery & join Is derived from an example in Noel Enete s Nuggets for Jini package whitney.jini.examples.hello; import java.rmi.remote; import java.rmi.remoteexception; public interface HelloInterface extends Remote

2 2 of 10 11/13/2007 7:35 AM public String sayhello() throws RemoteException; Doc 18, Simple Jini Example Slide # 3 HelloServer package whitney.jini.examples.hello; import net.jini.core.entry.entry; import net.jini.core.lookup.serviceid; import net.jini.lookup.entry.name; import com.sun.jini.lookup.serviceidlistener; import com.sun.jini.lookup.joinmanager; import com.sun.jini.lease.leaserenewalmanager; import java.rmi.remote; import java.rmi.remoteexception; import java.rmi.rmisecuritymanager; import java.rmi.server.unicastremoteobject; public class HelloServer extends UnicastRemoteObject implements HelloInterface, ServiceIDListener private ServiceID myid; public HelloServer() throws RemoteException public String sayhello () throws RemoteException return ("Hello World from Jini Hello server!"); public void serviceidnotify (ServiceID uniqueid) myid = uniqueid; System.out.println("server: ID set: " + myid ); Doc 18, Simple Jini Example Slide # 4 HelloServer Main public static void main (String[] args) throws Exception System.setSecurityManager (new RMISecurityManager ()); HelloServer myserver = new HelloServer (); Entry[] identityingattributes = new Entry[1]; identityingattributes[0] = new Name("HelloServer"); JoinManager mymanager = new JoinManager ( myserver, identityingattributes, myserver, new LeaseRenewalManager () ); System.out.println ("Server has been Joined!"); Doc 18, Simple Jini Example Slide # 5 HelloClient package whitney.jini.examples.hello; import net.jini.core.entry.entry; import net.jini.core.lookup.servicetemplate; import net.jini.core.lookup.serviceregistrar;

3 3 of 10 11/13/2007 7:35 AM import net.jini.core.discovery.lookuplocator; import net.jini.lookup.entry.name; import java.rmi.rmisecuritymanager; public class HelloClient 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 ("HelloServer"); ServiceTemplate template = new ServiceTemplate (null, null, serverattributes); HelloInterface myserverinterface = (HelloInterface) registrar.lookup (template); System.out.println ( myserverinterface.sayhello () ); Doc 18, Simple Jini Example Slide # 6 Example Explained The Client public static void main (String[] args) throws Exception System.setSecurityManager (new RMISecurityManager ()); LookupLocator lookup = new LookupLocator ("jini://eli.sdsu.edu"); ServiceRegistrar registrar = lookup.getregistrar(); Service Lookup net.jini.core.discovery.lookuplocator A utility class that performs unicast discovery for a Lookup service LookupLocator(String url) LookupLocator(String host, int port) Constructors The URL type is jini Default port for a lookup service is 4160 Translate CAFE-BABE from hex to decimal to get 4160 String gethost() int getport() ServiceRegistrar getregistrar() ServiceRegistrar getregistrar(int timeout) Perform unicast discovery and return the ServiceRegistrar object for the given lookup service.

4 4 of 10 11/13/2007 7:35 AM Doc 18, Simple Jini Example Slide # 7 Interface net.jini.core.lookup.serviceregistrar Methods Information about available services Class[] getentryclasses(servicetemplate tmpl) Object[] getfieldvalues(servicetemplate, int setindex, String field) Class[] getservicetypes(servicetemplate, String prefix) Object lookup(servicetemplate tmpl) ServiceMatches lookup(servicetemplate tmpl, int maxmatches) Returns the service object from an item matching the template String[] getgroups() Information about Lookup service Returns the groups that this lookup service is a member of. LookupLocator getlocator() LookupLocator for unicast discovery of lookup service. ServiceID getserviceid() Notifcation, Registration EventRegistration notify(servicetemplate tmpl, int transitions, RemoteEventListener listener, MarshalledObject handback, long leaseduration) ServiceRegistration register(serviceitem item, long leaseduration) Doc 18, Simple Jini Example Slide # 8 HelloClient Continued // Create ServiceTemplate used to match or find the server // we want Entry[] serverattributes = new Entry[1]; serverattributes[0] = new Name ("HelloServer"); ServiceTemplate template = new ServiceTemplate (null, null, serverattributes); HelloInterface myserverinterface = (HelloInterface) registrar.lookup (template); Interface net.jini.core.entry.entry Entry subclasses: Are used in identifying and matching services

5 5 of 10 11/13/2007 7:35 AM Contains public fields of non-primitive types Must have no-argument constructor All fields must be serializable Each field is serialized separately, so references between two fields of an entry will not be reconstituted to be shared references, but instead to separate copies of the original object If a field of an entry being fetched is cannot be deserialized for any reason then net.jini.core.entry.unusableentryexception will be thrown when Entry is a marker interface, it has no methods Matching Entries Doc 18, Simple Jini Example Slide # 9 Let T (for template) be an object of a subclass Entry Let E be an object of a subclass of Entry A field of an Entry object is a wildcard it its value is null The template T matches E if: The type of E must be that of T, or be a subtype of the type of T Fields with values in T must be matched exactly by the value in the same field of E. Wildcards in T match any value in the same field of E. MarshalledObject.equals is used to test equality of fields, not Object.equals This means the bytes generated by their serialized form must match, ignoring differences of serialization stream implementation (such as blocking factors for buffering). Class version differences that change the bytes generated by serialization will cause objects not to match. net.jini.core.lookup.servicetemplate Constructor ServiceTemplate(ServiceID serviceid, Class[] servicetypes, Entry[] attrsettemplates) Doc 18, Simple Jini Example Slide # 10 Entry[] attributesettemplates ServiceID serviceid Public Fields

6 6 of 10 11/13/2007 7:35 AM Class[] servicetypes ServiceTemplates are used to match for services A service template (tmpl) matches service item (item) a if: item.serviceid equals tmpl.serviceid If tmpl.serviceid is null then tmpl and item match if: item.service is an instance of every type in tmpl.servicetypes and item.attributesets contains at least one matching entry for each entry template in tmpl.attributesettemplates. Standard Entry Subclasses net.jini.lookup.entry Classes Some basic entry classes with their fields. All fields are Strings Address ServiceInfo Location Name country manufacturer building name locality model floor organization serialnumber room organizationalunit vendor Doc 18, Simple Jini Example Slide # 11 Comment postalcode version comment stateorprovince street Status & StatusType Status is base class from which other status-related entry classes may be derived. StatusType defines status types: ERROR NORMAL NOTICE WARNING

7 net.jini.entry.abstractentry Useful base class for entry types You don t have to use this class, but will save you some effort Doc 18, Simple Jini Example Slide # 12 Entry & JavaBeans Jini uses JavaBeans to display entry objects to humans You should have a JavaBean class for an Entry class that a human may interact with Let X be an entry class then: JavaBean Class Design Pattern The JavaBean class for X is called XBean For each field F in X class XBean has methods: setf() and getf() XBean has an no-argument constructor XBean implements net.jini.lookup.entry.beanentry XBean has methods followlink(), makelink() These methods set and get the bean s field that contains the bean s entry object Location Entry Example Location fields and LocationBean s methods Location building floor room LocationBean Entry followlink() getbuilding() getfloor() getroom() makelink(entry e) setbuilding(string x) setfloor(string x) setroom(string x) 7 of 10 11/13/2007 7:35 AM

8 8 of 10 11/13/2007 7:35 AM Doc 18, Simple Jini Example Slide # 13 HelloClient Matching The following code creates a simple template to use to find a service. The service id is set to null, so it is not used. Using the service ID would be faster, but we need to know it. We also set the servicetypes to null. This means the template will match any servicetypes. If we were looking for printers, we might set servicetypes to be an array containing a printer type. Jini does not define these servicetypes. They must be supplied by Jini developers. Only one entry template is given. Hence this service template will match any service that contains an entry of type "Name" or subtype of "Name" with the field "name" equal to the value "HelloServer". Entry[] serverattributes = new Entry[1]; serverattributes[0] = new Name ("HelloServer"); ServiceTemplate template = new ServiceTemplate (null, null, serverattributes); HelloInterface myserverinterface = (HelloInterface) registrar.lookup (template); Doc 18, Simple Jini Example Slide # 14 HelloServer public class HelloServer extends UnicastRemoteObject implements HelloInterface, ServiceIDListener private ServiceID myid; public void serviceidnotify (ServiceID uniqueid) myid = uniqueid; System.out.println("server: ID set: " + myid ); Each service has a unique service id net.jini.core.lookup.serviceid The id is unique over time and space with respect to all other service ids generated by all lookup services. The id is a 128-bit value, to insure this uniqueness. It is to be set by the lookup service. To re-register an existing service, or to register the service in any other lookup service, item.serviceid should be set to the same service id that was returned by the initial registration. Contains one method, serviceidnotify com.sun.jini.lookup.serviceidlistener The lookup service calls this method to provide the service its service ID.

9 9 of 10 11/13/2007 7:35 AM Doc 18, Simple Jini Example Slide # 15 HelloServer Main HelloServer myserver = new HelloServer (); Entry[] identityingattributes = new Entry[1]; identityingattributes[0] = new Name("HelloServer"); JoinManager mymanager = new JoinManager ( myserver, identityingattributes, myserver, new LeaseRenewalManager () ); com.sun.jini.lookup.joinmanager This class manages the join protocol for a service. It discovers and keeps track of which lookup services to join, registers with them, keeps the registration leases renewed, and keeps the attributes up to date. JoinManager(Object service, Entry[] attrsets, ServiceIDListener callback, LeaseRenewalManager leasemgr) addattributes(entry[] attrsets) addattributes(entry[] attrsets, boolean checksc) addgroups(string[] groups) addlocators(lookuplocator[] locators) Entry[] getattributes() String[] getgroups() ServiceRegistrar[] getjoinset() JoinManager Methods Get the list of lookup services that have currently been joined. LookupLocator[] getlocators() Get the list of locators of specific lookup services to join. modifyattributes(entry[] attrsettemplates, Entry[] attrsets) modifyattributes(entry[] attrsettemplates, Entry[] attrsets, boolean checksc) removegroups(string[] groups) removelocators(lookuplocator[] locators) setattributes(entry[] attrsets) setgroups(string[] groups) setlocators(lookuplocator[] locators) terminate() Doc 18, Simple Jini Example Slide # 16

10 10 of 10 11/13/2007 7:35 AM Copyright, All rights reserved SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA USA. OpenContent license defines the copyright on this document. Previous visitors since 18-Mar-99 Next