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J2EE Architecture and Design Patterns
Student: Fang FangAdvisor: Dr. Glen Qin
Date: 05/14/2005
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Agenda
Introduction to Architecture
J2EE Architecture Diagram
Distributed Programming Serviced
Modular-Based Development
J2EE Application Deliverable
J2EE Standards
Patterns Arose from Architecture
Gang of Four Patterns
Q & A
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Introduction to Arthitecture
Architecture is the overall structure of a system, and it
cancontain subsystems that interface with other subsystems
Architecture versus Design (level of details)
Architecture considers bunch of *abilities
CapabilityAvailability
ReliabilityManageability and
FlexibilityPerformanceScalabilityExtensibility, Validity,
ReusabilitySecurity
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J2EE Application I J2EE Application II
Client tier
Web tier
Business tier
EIS tier
Clientmachine
J2EEServer
machine
DataBaseServer
machine
ApplicationClient
Dynamic HTMLpages
JSP/Servlet
EnterpriseBeans
DatabaseDatabase
EnerpriseBeans
Multi-tiered J2EE applications
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Distributes Programming Services
Naming and Registration (JNDI)
Remote Method Invocation (RMI)
Protocols
Distributed Object Frameworks
Between user interface and business tiers HTTP, RMI, CORBA,
DCOM, JMS
Between business and persistence tiers JDBC, IDL to COM bridge,
JMS,plain socket, native APIs via JNIembedded in resource
adapters
- CORBA- Native Language Integration- Java/RMI- DCOM
XML
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EJB Distributed Nature (I)
EJB Container
BeanEJBObject
EJBHome
RemoteStub
Home Stub
Client
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EJB Distributed Nature (II)
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J2EE Modular-Based Development
Presentation tier developer
Bean provider
Application assembler
Component provider
Application server provider
EJB container provider
Staff be categories into different roles:
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J2EE Application Deliverable
Web archive(.war)
web.xml
EJB archive(.jar)
ejb-jar.xml
Client archive(.car)
application-client.xml
Enterprise archive (.ear)application.xml
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Deployment Descriptor Sample
...
This role represents everyone who is allowed full accessto the
Cabin EJB.everyone
everyoneCabinEJB*
CabinEJB*
Required
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J2EE Standards
CTS
J2EE SDK
Contains following specs
Together with below's offerings
EJB spec
Servlet spec
JSP spec
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Patterns Arose from Architecture andAnthropology - Christopher
Alexander
Is quality objective?
How do we get good quality repeatedly?
Look for the commonalities
...especially commonality in the features of the problem tobe
solved
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Moving from Architectural to SoftwareDesign Patterns
Adapting Alexander for software
The Gang of Four did the early work on design patterns(Gamma,
Helm, Johnson, Vlissides)
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Key Features of Patterns
Item
Description-------------------------------------------------------------------------------------------------------------Name
All patterns have a unique name that identifies them
Intent The purpose of the patternProblem The problem that the
pattern is trying to solveSolution How the pattern provides a
solution to the problem in the context
in which it shows upParticipants The entities involved in the
patternand collaboratorsConsequences The consequences of using the
pattern. Investigates the forces at
play in the patternImplementation How the pattern can be
implementedGeneric structure A standard diagram that shows a
typical structure for the pattern
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Enumerate GoF Patterns
Structural Patterns
AdapterBridgeCompositeDecoratorFacade
FlyweightProxy
Behavioral Patterns
Chain of ResponsibilityCommandInterpreterIteratorMediator
MementoObserverStateStrategyTemplate MethodVisitor
Creational Patterns
Abstract FactoryBuilderFactory MethodPrototypeSingleton
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Abstract Factory Pattern
Provide an interface for creating families of related or
dependentobjects without specifying their concrete classes." -
GoF
Solution
A Switch to Control Which Driver to Use
class ApControl {. . .
public void doDraw() {. . .switch (RESOLUTION) {
case LOW:// use lrdd
case HIGH:// use hrdd
}}
public void doPrint() {. . .switch (RESOLUTION) {
case LOW:// use lrpd
case HIGH:// use hrpd
}}
}
Problem class ApControl {. . .
public void doDraw() {. . .myDisplayDriver.draw();
}public void doPrint() {. . .myPrintDriver.print();
}}
abstract class ResFactory {abstract public DisplayDriver
getDispDrvr();abstract public PrintDriver getPrtDrvr();
}
class LowResFact extends ResFactory {public DisplayDriver
getDispDrvr() {
return new LRDD();}
public PrintDriver getPrtDrvr() {return new LRPD();
}}class HighResFact extends ResFactory {...}
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The Facade Pattern
Provide a unified interface to a set of interfaces in a
subsystem.Facade defines a higher-level interface that makes the
subsystemeasier to use. - GoF
Problem Solution
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Stragegy Pattern
Solution
Define a family of algorithms, encapsulate each one, and
makethem interchangeable. Strategy lets the algorithm
varyindependently from clients that use it. - GoF
Problem
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J2EE Best Practice MVC Pattern (I)
Model
Controller
View
Represents the application data along with methods thatoperate
on that data.
Displays that data to the user.
Translates user actions such as mouse movement and keyboardinput
and dispatches operations on the Model.
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J2EE Best Practice MVC Pattern (II)
Http request
or post
Response
Forward
Dispatch
Update
Extract
Client browser
Controller(action servlet)
Businesslogic
Model(server sideJavaBean/EJB)
View(JSP page)
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Q & A
Thank you!!
