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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!
