1 Vrijendra Gokhale, Bernard Menezes K. R. School of Information Technology IIT Bombay User Interfaces for Jini Services The Jini Pattern Language Workshop.

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Vrijendra Gokhale, Bernard Menezes

K. R. School of Information TechnologyIIT Bombay

User Interfaces for Jini Services

The Jini Pattern Language WorkshopOOPSLA – 2000

15 October 2000 User Interfaces for Jini Services

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Pervasive Computing

• Computing as a technology that hides, like paper

• Devices around us have increasing computational power

• Future wireless networks are going to be increasingly dynamic


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Context Aware Computing

• Control: ability to control things around me

• Data manipulation: ability to gather data from gadgets around me and process it

• Customization: does the environment adapt to my needs?


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The Jini Technology

• A federating technology for services

• Enables impromptu communities• Supports service discovery based

on attributes• Based on the Java Remote Method

Invocation (RMI)


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Key Jini Features

• Discovery• Lookup• Leasing• Remote Events• Transactions

Proxy publishing and lookup

Soft State and automatic cleanup


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A Jini Scenario

• Service discovers a Jini Lookup

Multicast request

Lookup proxy


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A Jini Scenario

• Service publishes a proxy at the lookup

Join Protocol


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A Jini Scenario

• Client discovers a Jini Lookup

Multicast request

Lookup proxy


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A Jini Scenario

• Client looks up the printer

Lookup

Printer proxy


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A Jini Scenario

• Client uses the print service of the printer

print()


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The Lego Example!


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A Hypothetical Situation

“You enter a room which contains appliances like printers, cameras, music systems, microwave ovens… is it possible to control, compute or manipulate these gadgets without any prior knowledge of their existence?”


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Issues: A Hypothetical Situation• To programmatically talk to a Jini service

the client must have the service interface• Does the client carry ALL the interfaces it

needs to talk to [impractical]• How to handle gizmos?

Something the Martians left behind!(assuming it participates in a Jini federation)


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Issues: A Hypothetical Situation• Can a common Jini interface allow

service specific behaviour?• Does the client have a JVM?


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Solution: User Interfaces

• All interactive services export UIs.• Programmatically such services

are known by a well known interface.

public interface JUnknown{

public void getBuilder(String id);

}


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Using Patternsto Accommodate Varied Client Display Technologies

• A Factory encapsulates client side UI capabilities

public interface Factory{

public Object getObject(Object which);

}


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Using Patternsto Accommodate Varied UI Construction Logic

• A Builder encapsulates client UI technology specific UI construction logic

public interface Builder {

public void buildUI (Factory factory);

}


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• the getBuilder(String id)method of JUnknown dynamically loads the appropriate builder for the specified client factory type!

• this uses underlying RMI class loading mechanisms

JUnknown ties it all customized UI construction for different client devices


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Interactions and code


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Interactions and code


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Advantages

• Dynamically builders can be loaded for various factory types

• Support for different display technologies

• Stub is lightweight and does not carry any extra UI classes

• Dynamically builders can be loaded for various factory types

• Support for different display technologies

• Stub is lightweight and does not carry any extra UI classes


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More Advantages

• Adding support for new UI tech by simply adding new builders at service end

• Support for Non JVM clients viz web clients– Using an intermediate tier viz Servlets– Involves an HTMLFactory and

HTMLBuilder


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Future Work

• Identifying and refining the UI patterns

• Security in Jini– Who can access services?

Authentication– Who can invoke what service?

Authorization


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Thank You!

1 Vrijendra Gokhale, Bernard Menezes K. R. School of Information Technology IIT Bombay User Interfaces for Jini Services The Jini Pattern Language Workshop.

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