Developing Java Web Applications 120276364738927 5

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Developing Java Web

Applications

Dr. Harry Chen

CMSC 491S/691S

February 11, 2008
http://harry.hchen1.com/http://socailwebtechnologies.blogspot.com/http://socailwebtechnologies.blogspot.com/http://harry.hchen1.com/http://www.umbc.edu/umbcstyle/images/verthires.jpg


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Agenda

Web application architecture

Java Servlet technology

WebWork: building webapps made easySpring: Inversion of Control (IoC)

Maven: Java project management and

build tool
http://www.umbc.edu/umbcstyle/images/verthires.jpg


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A canonical Web architecture

Do you see any technical issues in this architecture?

Source: http://www.ibm.com/developerworks/ibm/library/it-booch_web/


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Stateless communication

Communications

between your browser

and the Web Server

is usually stateless Cookie was

invented to solve this

problem.


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Thin client vs. Thick (fat) client

Where do you place

your business logic?

Thin client: most of

the business logic liveon the client side

Thick client:

application states are

managed by the

serverThin clients live here.

Thick clients live here.


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How do we create View?

Raw data must beprocessed before itspresented to the user.

Users see the View(HTML, PDF, RSSetc.)

Should you hardwire

code in the businesslogic to generateViews?

Raw dataView (HTML, PDF, etc)

How will be the Views be generated?


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Overhead in access data

A major part of theapplicationimplementationconsists of accessingand updating the rawdata which can becostly.

Reduce this overheadcan speed up yourdevelopment (i.e.,save cost)

SQL DBHTML

Do I have to call

SELECT,

INSERT,

UPDATE all the

time?


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Framework

Software engineering is like civil

engineering: we need framework.

Option 2: Use framework Your Goal

Option1: Build everything from scratch


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http://en.wikipedia.org/wiki/OnTaphttp://en.wikipedia.org/wiki/Model-Gluehttp://en.wikipedia.org/wiki/Model-Gluehttp://en.wikipedia.org/wiki/Model-Gluehttp://en.wikipedia.org/wiki/Mach-IIhttp://en.wikipedia.org/wiki/Mach-IIhttp://en.wikipedia.org/wiki/Mach-IIhttp://en.wikipedia.org/wiki/Fusebox_%28programming%29http://en.wikipedia.org/wiki/ColdSpringhttp://en.wikipedia.org/wiki/ColdFusion_on_Wheelshttp://en.wikipedia.org/w/index.php?title=ColdBox&action=edithttp://en.wikipedia.org/wiki/Symfonyhttp://en.wikipedia.org/wiki/Simplicity_PHP_frameworkhttp://en.wikipedia.org/wiki/Seagull_PHP_Frameworkhttp://en.wikipedia.org/wiki/QPHP_Frameworkhttp://en.wikipedia.org/wiki/Qcodohttp://en.wikipedia.org/wiki/PRADOhttp://en.wikipedia.org/wiki/PostNukehttp://en.wikipedia.org/wiki/PHPOpenbizhttp://en.wikipedia.org/wiki/PHP_For_Applicationshttp://en.wikipedia.org/wiki/MODxhttp://en.wikipedia.org/wiki/KohanaPHPhttp://en.wikipedia.org/wiki/Joomla%21http://en.wikipedia.org/wiki/Horde_%28software%29http://en.wikipedia.org/wiki/Fuse_Frameworkhttp://en.wikipedia.org/wiki/Epesihttp://en.wikipedia.org/wiki/Drupalhttp://en.wikipedia.org/wiki/DIY_Frameworkhttp://en.wikipedia.org/wiki/CodeIgniterhttp://en.wikipedia.org/wiki/Canvas_Frameworkhttp://en.wikipedia.org/wiki/CakePHPhttp://en.wikipedia.org/wiki/Antares_Frameworkhttp://en.wikipedia.org/wiki/Akelos_PHP_Frameworkhttp://en.wikipedia.org/wiki/Mason_%28Perl%29http://en.wikipedia.org/wiki/Maypole_frameworkhttp://en.wikipedia.org/wiki/Interchange_%28software%29http://en.wikipedia.org/wiki/Catalyst_%28software%29http://en.wikipedia.org/wiki/ZTemplateshttp://en.wikipedia.org/wiki/ZK_Frameworkhttp://en.wikipedia.org/wiki/Wicket_frameworkhttp://en.wikipedia.org/wiki/WebWorkhttp://en.wikipedia.org/wiki/WebObjectshttp://en.wikipedia.org/wiki/ThinWirehttp://en.wikipedia.org/wiki/Tapestry_%28programming%29http://en.wikipedia.org/wiki/Stripes_%28framework%29http://en.wikipedia.org/wiki/Spring_Frameworkhttp://en.wikipedia.org/wiki/SmartClienthttp://en.wikipedia.org/wiki/Shale_Framework_%28software%29http://en.wikipedia.org/wiki/RIFEhttp://en.wikipedia.org/wiki/Reasonable_Server_Faceshttp://en.wikipedia.org/wiki/Oracle_ADFhttp://en.wikipedia.org/wiki/OpenXavahttp://en.wikipedia.org/wiki/OpenLaszlohttp://en.wikipedia.org/wiki/Makumba_%28framework%29http://en.wikipedia.org/wiki/JBoss_Seamhttp://en.wikipedia.org/wiki/JavaServer_Faceshttp://en.wikipedia.org/wiki/ItsNathttp://en.wikipedia.org/wiki/IT_Mill_Toolkithttp://en.wikipedia.org/wiki/ICEfaceshttp://en.wikipedia.org/wiki/Hamletshttp://en.wikipedia.org/wiki/Grails_%28Framework%29http://en.wikipedia.org/wiki/Google_Web_Toolkithttp://en.wikipedia.org/wiki/Flexivehttp://en.wikipedia.org/wiki/Clickhttp://en.wikipedia.org/wiki/Aranea_frameworkhttp://en.wikipedia.org/wiki/AppFusehttp://en.wikipedia.org/wiki/Apache_Strutshttp://en.wikipedia.org/wiki/Apache_Cocoonhttp://en.wikipedia.org/wiki/ASP.NET_MVC_Frameworkhttp://en.wikipedia.org/wiki/Component-based_Scalable_Logical_Architecturehttp://en.wikipedia.org/wiki/DotNetNukehttp://en.wikipedia.org/wiki/Monorail_%28.Net%29http://en.wikipedia.org/wiki/Yahoo%21_UI_Libraryhttp://en.wikipedia.org/wiki/Spry_frameworkhttp://en.wikipedia.org/wiki/SmartClienthttp://en.wikipedia.org/wiki/Script.aculo.ushttp://en.wikipedia.org/wiki/Rico_%28Ajax%29http://en.wikipedia.org/wiki/Rialto_Toolkithttp://en.wikipedia.org/wiki/Qooxdoohttp://en.wikipedia.org/wiki/Prototype_JavaScript_Frameworkhttp://en.wikipedia.org/wiki/OpenLink_AJAX_Toolkithttp://en.wikipedia.org/wiki/MooToolshttp://en.wikipedia.org/wiki/Mochikithttp://en.wikipedia.org/wiki/Microsoft_AJAX_Libraryhttp://en.wikipedia.org/wiki/JQueryhttp://en.wikipedia.org/wiki/Ext_%28javascript_library%29http://en.wikipedia.org/wiki/Echo_%28framework%29http://en.wikipedia.org/wiki/Dojo_Toolkithttp://en.wikipedia.org/wiki/Clean_AJAXhttp://en.wikipedia.org/wiki/Backbasehttp://www.umbc.edu/umbcstyle/images/verthires.jpg


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Servlets are Java code that run in a server

application (e.g., Tomcat) and answer

client request.

Source: http://www.informit.com/articles/article.aspx?p=26920


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HelloWorld Servlet

Set HTTP Header: Content-Type (HTML)

Creates the HTML page content

Implementation that handles HTTP GET request

Outputs the HTML into the HTTP Response

Do you see any technical issues with this implementation?

Source: http://www.informit.com/articles/article.aspx?p=26920


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JSP (Java Servlet Pages)

Technology that allows Java code and

certain pre-defined actions to be

embedded into static content.

Java Servlet:

Write codecompiledeploy

JSP

Write codedeploy


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HelloWorld JSP

Source: http://mainline.brynmawr.edu/~dkumar/JSP/

Use Java as if its a scripting language


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Open issues in Java Servlet technology

No mention of any framework or design

pattern for building web applications

How to handle stateless communication?

Use Thin or Thick client?

How to access data?

How to create Views?


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Example: J2EE webapp

This is what you want to build.


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Example: J2EE webapp (cont.)

This is an MVC solution

All DB access and update

operations are implemented here.

All business logic and applications

states are stored here.

HTML, PDF and whatever goes here.

They read and parse data object from

the Model


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Problems with MVC

MVC is only a design patterni.e., you

still have to write code to follow this

specification

An obvious problem is that everyone has

to learn and write their own MVC

framework


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WebWork


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WebWork

A Java MVC framework that help

developers to minimize code and to be

more concentrated on business logic and

modeling.

Less plumbing code, more useful code.

http://www.opensymphony.com/webwork/
http://www.amazon.com/exec/obidos/tg/detail/-/1932394532/qid=1128052468/sr=8-1/ref=pd_bbs_1/104-0806192-0414332?v=glance&s=books&n=507846http://www.umbc.edu/umbcstyle/images/verthires.jpg


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WebWork terminology

Action: a piece of code that is executed when a

URL is visited

Bean: a data object that holds useful application

information Views: templates pages for generating outputs

for the clients to consume.

Result: the output created by a template page


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WebWork workflow

Read: http://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.html
http://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.javaworld.com/javaworld/jw-03-2004/jw-0329-webwork.htmlhttp://www.umbc.edu/umbcstyle/images/verthires.jpg


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WebWork HelloWorld

Goal: Go a URL, the webapp outputs

Hello World!

3 Steps

Create an Action class to handle the request

Create a View (template) to produce HTML

Configure Action and View


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Action: HelloWorld.java

Extends a standard Action

superclass.

Implement the business logic

How to access the Bean (the

message)


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View: helloworld.jsp

Use JSP Tag lib to access our Bean

(the message)

If you dont like to use JSP, you have other options: Freemarkerand Velocity


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WebWork Configuration: HelloWorld

Edit xwork.xml to glue the Action with the

Template view.

Define our Action and name it

helloworld

If the action returns success, then

apply the hello.jsp template


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WebWork: HelloWorld Output

Read: http://www.javaworld.com/javaworld/jw-10-2005/jw-1010-webwork.html


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Spring IoC


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Dynamic object instantiation

Often your business logic implementation

requires runtime configuration

Customer Relationship App may use a different

JDBC connection to access a new customer DB

Dynamically fine tune how many threads the

robot should instantiate for building search

index DB

Configure the username, password and DB url

for your JDBC connection.


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Inversion of Control (IoC)

IoC is a principle that encourage the

decoupling of code.

A.K.A. Dependency Injection.

Problem: The use of MovieFinderImpl is hardwired into

MovieLister. Change this logic will require code rewrite and

re-compile MovieFinderImpl

Read: http://martinfowler.com/articles/injection.html


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IoC Solution

Introduce an intermediate component to

handle the assembly of class objects.

Solution: If you want to use a different MovieFinder, just

change how Assembler calls .


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Spring IoC

A framework that can be coupled with

WebWork to provide Dependency

Injection.

Spring IoCimplements a

flexible Assembler.

Developers can tell this

Assembler how to

perform viaXML configuration.

http://static.springframework.org/spring/docs/2.0.x/reference/beans.html


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Spring IoC: HelloWorld in gnizr

How HelloWorld Action is instantiated in

gnizrs HelloWorld demo

http://code.google.com/p/gnizr/wiki/HelloWorldDemo


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Spring IoC: a more complex example

(1) The Class object folderTagListener is dynamically associated with

bookmarkManager via a configuration file, not hardwired in the source of

bookmarkManager. (2) Developers also fine tune the number of WorkerThread to be

instantiated by bookmarkManager in the same configuration file.

(1)

(2)


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Apache Maven


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Jave project management

It concerns the management of

library dependency,

code building,

unit testing,

packaging and

documentation.

- Why do you think its

important to consider those

issues when building

software?

- Can you relate to what youhave experienced in the

past (in school or at work)?


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Problems I have faced

When some JAR library changed, I have tomanually download the JAR from the projectweb site.

Make sure dependency library are included inmy CLASSPATH for building and testing

Decide the directory layout of my project (whereis src, classes, resources).

Figure out how to write documentation and calljavadoc in my project.


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Apache Maven

Maven is an open source Java project

management tool that simplifies many of

the tedious tasks associated with Java

programming.

Features I love very much:

Library dependency management

Build, test, and package

Pre-defined directory layout for webapp dev.

http://maven.apache.org/


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POM file

In Make, we have Makefile

In Maven, we have POM file (pom.xml)

In this POM file, you can define

JAR (version and package names) that should to beincluded in your build CLASSPATH (dependencies).

The layout of your project (where do you keep source,.class, other resources and configuration)

Information for generating documentation

And many other stuff


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Maven: Create a project


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Maven: POM file


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Maven: build package


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Try Maven in 5 minutes

http://maven.apache.org/guides/getting-started/maven-in-five-minutes.html
http://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://maven.apache.org/guides/getting-started/maven-in-five-minutes.htmlhttp://www.umbc.edu/umbcstyle/images/verthires.jpg


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Summary

Building a successful and maintainable Java

Web application requires the effective use of

software frameworks and development tools.

WebWorkand Springare excellent frameworksfor building scalable and high-quality Java Web

applications.

Apache Mavensolves many project

management issues that programmers havebeen struggling for a long time.

Developing Java Web Applications 120276364738927 5

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