Building Web Applications With J2EE

8/2/2019 Building Web Applications With J2EE

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Building Web ApplicationsWith J2EE

OhioedgeEnterprise Java Solutions Provider

Since 1996

By Sandeep Dixit, Partner


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Assumptions

Audience Background

Elementary knowledge of J2EE

Currently planning or in the process ofbuilding Web applications with J2EE


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Assumptions

Audience Expectations

Want to learn or verify essential concepts

of Web application development withJ2EE

Want to see live demonstrations of sample applications

deploying sample applications in J2EE-compliantapplication server

how a proper implementation of these concepts results inrobustness, quality, and improved productivity


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Todays Agenda

Origin of J2EE

Mindset for building Web applications

Generalization: J2EE Patterns Three-tier component: EJB-JavaBean-JSP

XML schema-driven applications

Directory structure: Effective organization of java,

jsp, xml, sql and bat script files Package structure: Effective grouping of Java and

JSP source code

Live Demonstration of J2eeBuilder Framework &component plug-in


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J2EE Facts

J2EE is not a programming language.

J2EE is a specification for writing enterpriseapplications (distributed computing)

J2EE specification compliant code is

portable between J2EE-compliantapplication servers.


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1985-1992

One programming language for building

distributed (client-server) applications IDE for compilation, debugging,

execution and file management

Procedural programming


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1990+

VB brings client-server (distributed)

application development environment todesktops

Procedural programming

GUI development is more user-friendly


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1995+

Java, an OS independent, pure Object-

oriented, programming language startsgaining ground

Object-oriented programming is more

user friendly Java Remote Method Invocation (RMI) is

made available for distributed computing


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1997+

Apache Web Server becomes de-facto

web server Java RMI is further strengthened by a

specification - J2EE specification - on

how to write an RMI server. Developing distributed applications is

made more user friendly.


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1999+

Servlet/JSP makes HTML-based Web GUI

a real thing for enterprise applications Object-oriented programming is further

extended into XML definition driven

object-oriented programming J2EE incorporates XML as the way to

specify data


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2000+

Enthusiastic software developers start

using J2EE. Container Managed Persistence becomes

a reality

Methodologies for writing J2EEapplications are discovered.


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2001+

Various articles, papers, and books on

J2EE Patterns, Practices, and Strategiesare published and presented

Jboss an open-source J2EE 1.3-compliant

application server is used by more than 1Million developers world-wide

J2EE is free. J2EE is open. J2EE is here

to stay.


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Mindset for building Web

applications

Think in terms of Servicing a request

For example, a click on a create buttonon a customer page in a browser is arequest.

Building a Web application requires anapproach of handling and processing httprequests and sending appropriate

responses back to the requesters

Application

Server

CRM


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Generalization of Services

Generalization of how http requests are

serviced by presentation-tier, middle-tier,and data-tier results in a generic, inter-tier dependent, reusable library of sourcecode - J2EE patterns


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Generalization of Services

For an example, the application processing customer-createrequest needs to verify if the requester is valid, requesters session isvalid, and license to use application itself is valid. These validation

steps are independent of customer-create request and areapplicable to any requests such as, customer-delete, contact-find,etc.

This requires that every time a request is received it should be firstpassed-on to a generic validation service that would either permit

or deny further servicing of the request.

Typically, validation service would get categorized underpresentation services. Depending upon the layer where theservices are called, they would be categorized under either -presentation, business, or data services.


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Servicing a request

Http request originates in a browser

Http response ends in the browser

URL

Presentation-tier

Business-tier


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J2EE Patterns: Presentation-tier

Front Controller

View Helper

Composite View

Service To Worker

Dispatcher View


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Brief overview of

Presentation-tier patterns Front Controller: Provides a centralized controller for

managing the handling of a request

View Helper: Encapsulates logic that is not related topresentation formatting into Helper components

TheViewController

*.ctrl


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Brief overview of

Presentation-tier patterns Dispatcher View: Similar to Service To Worker; Dispatcher plays a limited role

in the processing of requests - Dispatcher plays limited to moderate role inview management.

Limited role: No outside resources are utilized in order to choose the view. The informationencapsulated in the request is sufficient to determine the view to dispatch the request. Forexample: http://my.server.com/myContextRoot/Controller?next=login.jsp

Moderate role: The information contains an action to be completed:http://my.server.com/myContextRoot/Controller?action=login The responsibility of thedispatcher component here is to translate the logical name login into the resource name of anappropriate view, such as login.jsp, and dispatch to that view. To accomplish this translation, thedispatcher may access resources such as an XML configuration file that specifies the appropriate

view to display.

Service To Worker: Combines a Dispatcher component with the FrontController and View Helper patterns - Dispatcher plays moderate to largerole in view management. Dispatcher is more sophisticated. The dispatchermay invoke a business service to determine the appropriate view to display. For example: http://my.server.com/myContextRoot/Customer.ctrl?submit=Set


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Service To Worker

URL

Business-tier


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Processing the request

URL

Service

Locator

Value

Object

Requests EJB/BusinessService

Locates

Business

Service

EJBBusiness

Delegate


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J2EE Patterns: Business-tier

Business Delegate

Value Object

Session Faade

Composite Entity

Value Object Assembler

Value List Handler

Service Locator


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Brief overview of Business-tier

patterns Business Delegate: De-couples presentation and service tiers,

and provides a faade and proxy interface to the services.

Value Object: Facilitates data exchange between EJB andBusinessDelegate

Value List Handler: Manages query execution, results caching,and results processing.

Service Locator: Encapsulates complexity of business servicelookup and creation; locates business service factories.


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J2EE Patterns for Servicing

Requests Front Controller

View Helper

Composite View

Service To Worker

Dispatcher View

Business Delegate

Value Object

Session Faade

Composite Entity

Value Object Assembler

Value List Handler

Service Locator

Service Activator

Data Access Object

Business-tierPresentation-tier Data-tier


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Directory Structure

Source Code

Scripts

J2EE Specification Code ejb.xml web.xml application.xml

J2EE Application Specific Code jboss.xml

jboss-web.xml Java/Jar Specific Code

manifest.mf


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Package Structure

Business Functionality code

extends framework code

Framework code

implementation of patterns


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J2eeBuilder Framework

Demonstration of a framework

Implementation of patterns

Session Management

User Management

License Management

j2eebuilder-config.xml

Demonstration of plugging-in a product componentinto the framework


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Summary

J2EE is Java, EJB specification, Servlet, JSP, Html, and XML

Use open-source software such JDOM, LOG4J, Apache Web Server,

Tomcat Servlet Container, and JBoss Application Server Document your architecture, data-structure, functional scope,

directory structure, and package structure, before launching a full-scale development

Understand key concepts. Learn to do-it by hand using simple

TextPad before using IDEs.

Keep it J2EE compliant. Avoid getting locked into any vendor specifictechnology.

You build a generic framework and robustness, quality andproductivity will come.


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Q & A

Documents

Building Web Applications With J2EE