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Jini: A Java-Based Distributed Framework - Overview and Usage - Prof. William Pugh, Study notes of Programming Languages

University of MarylandProgramming Languages
Prof. William Pugh

An overview of jini, a java-based distributed framework that offers services and registries, distributed events, transactions, and javaspaces. It covers the process of providing and finding services, using proxies, lookup services, and leasing. The document also mentions the use of jini in various networks and the concept of attribute lookup.

Typology: Study notes

Pre 2010

Uploaded on 07/30/2009

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koofers-user-7tj-1 🇺🇸

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Jini
CMSC 433
2
Jini overview
• Framework and services on top of Java RMI
– finding services
• finding registries
• searching registries
• keeping registries up to date
– Distributed events
– Transactions
– JavaSpaces
• Shared store
3
Providing Services
Lookup
Service
Printer
Service
Proxy
Printer
Interface
registration
4
Finding providers
Lookup
Service
Printer
Service
Printer
Proxy
Printer
Client
Printer
Interface
Printer
Proxy
5
Using Services
Lookup
Service
Printer
Service
Printer
Proxy
Printer
Client Printer
Proxy
6
Proxies
• Java classes that implement standard
interfaces
• Classes get downloaded as needed
– From http server?
• Proxies can use any mechanism to
communicate with service
– RMI stubs, local computation and any
communication medium
pf3
pf4

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Download Jini: A Java-Based Distributed Framework - Overview and Usage - Prof. William Pugh and more Study notes Programming Languages in PDF only on Docsity!

Jini

CMSC 433

2

Jini overview

  • Framework and services on top of Java RMI
    • finding services
      • finding registries
      • searching registries
      • keeping registries up to date
    • Distributed events
    • Transactions
    • JavaSpaces
      • Shared store

3

Providing Services

Lookup Service

Printer Service

Proxy InterfacePrinter

registration

4

Finding providers

Lookup Service

Printer Service

PrinterProxy

Printer Client

InterfacePrinter PrinterProxy

5

Using Services

Lookup Service

Printer Service

PrinterProxy

Printer Client

PrinterProxy

6

Proxies

  • Java classes that implement standard interfaces
  • Classes get downloaded as needed
    • From http server?
  • Proxies can use any mechanism to communicate with service - RMI stubs, local computation and any communication medium

7

Lego Mindstorm Proxies

  • An example: Proxies for Lego Mindstorm robots
  • Processor on Mindstorm not powerful enough to host a JVM
  • Proxy can keep state about robot, communicate through infrared link

8

Lookup services

  • Broadcast looking for lookup services messages
  • Each lookup service on network responds with a proxy
  • Queries to lookup service are done through proxy - actual communication with lookup service is up to proxy

9

Using a lookup service

  • Can specify a list of classes/interfaces
    • only interested in results that are subtypes of all
  • Can specify attributes
    • Location { String building; String floor; String wing; }
    • must match all attributes (^10)

Service ID’s

  • When services first register, they are assigned a service ID - 128 GUID
  • a particular service using the same service ID on all lookup services - if you get the same service back from multiple lookup services, can detect duplicates

11

Leasing

  • When a service registers with a lookup service, it gets a limited duration lease - if lease expires without being renewed, service is de-listed
  • Service must renew lease
    • makes sure service is still up and still reachable from lookup service

12

Finding lookup services, revisited

  • When a service is activated, broadcasts request to find lookup services - using multicast over local net
  • When lookup service is activated, and at periodic intervals, broadcasts “I’m a lookup service” - services that learn about new lookup services register with them

19

JavaSpace operations

  • write - add an entry
  • read - find a matching entry
    • Can wait for matching entry (with timeout)
  • notify - add listening for matching entries
  • take - read and delete atomically

20

JavaSpace matching

  • Entry’s match just like Jini lookup attributes
  • Can provide don’t cares
  • Can use subtyping