Case Study PrintService

- dynamically networked products, services, and applications

- network computer / consoles (powerful processor, several MB of memory)

©2001 Jerome Colombie

Infrastructure Requirements

• Java 2 platform, Standard Edition (J2SE) (May 8, 2000)

• Jini is written purely in Java• JVM (powerful processor, several MB

of memory)• JRE 1.3 / JDK1.2.* (Solaris / Windows / Linux)

• network (TCP/IP)

Infrastructure Requirements 2

Software Requirements

• http-server (Class files, centralized, distributed)

• lookup-service reggie• rmid (Activation, power saving, activatable hardware with

standby) lease manager, lookup manager

Programming Requirements

• Discovery (Unicast / Multicast for maximum flexibility)

• Three Tiers (Thin-Client, dynamic GUI/driver, Print-Service)

• Thin-Client searches for specific Interface (Attributes: Address (vendor), Location, ServiceInfo, ServiceType, Status)

• GUI/driver (Transformation of Input-File, Printer-Selection)

• PrintService (Hardware abstraction, job-scheduling, billing data)

Prgramming Requirements 2

Client PrintManager (GUI / Driver)Printer

PrintService

Interface Requirements

• Client / Server must share common Interface

• Beans (get and set methods for attributes)getAttribute(name, value)setAttribute(name, value)

• Attributes (Entry[], service specific attributes: driver, supported file-formats or languages, security-levels)

Attributes

• Find Service (Printer, Movieplayer, PCMCIA-Cards, wordprocessor)

• Load Interface (Entry[], TypeInfo, ServiceInfo, Manufacturer)

• Find Driver for Service (Printer driver, plug-ins, application from specific vendor)

Interface PrintService.java

PrintService.java

import java.rmi.*;

public interface PrintService { public String print(String file) throws RemoteException; public boolean setAttributes(String room, String device,

String format, String copies, boolean flagboolean psnup) throws RemoteException;

}

Interface PrintManager.java

PrintManager.java

import java.rmi.*;

public interface PrintManager { public boolean start(String clientinfo) throws RemoteException;}

What do we get?

• Dynamic loading of services without configuration or user-intervention

• the implementation of services is loaded dynamically, at runtime

• no administration (little) needed, ideal for dynamic environments

• A Jini Community is self-healing. (Printer failure)

Service registration

Client PrintManager (Driver)

PrintServicePrintService register

PrintManager register

LUS

Discovery / Loading

Client PrintManager (Driver)

LUS

1. Discover Print- Manager

2. Load PrintManager

(Local Execution)

Discovery / Printing

Client PrintManager (Driver)

LUS

1. Discover Print- Service

2. Print

Problems:

• Service Interfaces must be specified (a server is an implementation of a service)

• Interface is crucial. Both client and server know it.

• Jini Community (Developers) define set of common and ubiquitous interfaceshttp://www.jini.org/

• Generic Interface (Use object reflection to learn the interface of a service, extendible)

Areas of application

• large systems (scalability)• environments sensitive to security and

fail-safety (robustness)• distributed systems• Ad-hoc networks

Key Features:

• open standards based environment• Provides cross-platform compatibility,

safe network delivery, and smartcard to supercomputer scalability

• dynamically networked products, services, and applications that scale from device to the enterprise

• rapid and cost effective development

Official Case Study from Sun:

• Jini[tm] Network Technology Drafted for Service in the U.S. Army

• Tactical Operation Centers• control, execute, plan, and monitor battlefield maneuvers• introduce new computing and communications elements into

the network under battle conditions• independent of computer re-starts, device drivers, system re-

configurations, and extensive technical support• increased TOC mobility and functionality