Web Applications and Struts2

8/8/2019 Web Applications and Struts2

1/24

WebA lications


2/24


3/24

Separationofapplicationlogicandmarkup

Easierto

change

and

maintain

Lesserrorprone

Accesstofunctionalitytosolveroutineneeds

Datatransferbetweenclient HTTP andserver Java

Validation

Internationalization Userinterfacecomponents(tags)


4/24

Struts2sitsontopoftwoimportanttechnologies

Webframework (Struts2)

HTTP


5/24

Seriesofclientservermessageexchanges

Designedfor

static

HTML

rather

than

dynamic

Stateless(howtodothingslikeauthentication?)

Text based(howtomaptoandfromJavatypes?)

Requestfor

aresource

Application or

webserver

Web

browser

Response


6/24

ProvidesintuitiveobjectorientedabstractionofHTTP:

Servlet(HttpServlet)

SmallJavaprogram

ReceiveandrespondtorequestsfromWebclients

Objectrepresentingaclientrequest

Accessto arameters re uestURL in utstream

Response(HttpResponse)

Objectrepresenting

aserver

response

Accesstocontenttype,header,writer


7/24

Session

Provides

a

session

between

multiple

requests

AllowsServletstobindobjectsandmanipulateinformation

Filter Performsfilteringonrequestsand/orresponses

Configuredinweb.xml

Useful

for

authentication,

logging


8/24

ServletsarepackagedintowebapplicationsasWARfiles

Zip

file

with

a

specific

structure on a ns:

Servlets

Webresources

(HTML,

CSS,

templates,

images)

Dependentlibraries(JARs)

/ Web resources (HTML, CSS, templates, images) /WEB-INF Private files (not returned by Web server) /WEB-INF/web.xml Deployment descriptor / configuration file /WEB-INF/classes Java classes /WEB-INF/lib Depdendent libraries / JARs


9/24

WebapplicationsaredeployedinServletcontainers

Implementation

of

the

Servlet

specification

PopularopensourceversionsareTomcatandJetty

Servlet container

http://localhost:8080/WebAppC/ServletB

ServletA ServletC

ServletB

WebAppAServletB

WebAppCServletB


10/24

Solvingapplicationlevelconcerns/routinework!

Binding

request

parameters

to

Java

types

Providinginternationalization

Renderin resentationla er HTMLetc

Makingcalls

to

business

layer


11/24

Purposes

Encapsulates

the

work

to

be

done

for

a

request

Determinewhichresultshouldrendertheview

public class InvertStringAction implements Action{

private String word;// set-method

pr vate tr ng nverte or ;// get-method

public String execute()

{ if word == null word.trim .len th == 0{

return INPUT;}

invertedWord = getInvertedWord(); // implemented another place

return SUCCESS;

}}


12/24

ActionSupport:Abstract convenienceclassproviding:

Validation

Workstogetherwithinterceptorsinthedefaultstack

ActionContext:Container

holding

relevant

data

for

arequest:

ValueStack

Requestparameters

Sessionvariables

Applicationattributes


13/24

Transfersdatadirectlyontomodelobjects

Avoids

tedious

object

creation

code

ProvidedbyinterfaceModelDriven

xposesme o ge o e


14/24

public class SaveStudentextends ActionSupport implements ModelDriven

{

private Student student = new Student();

Class extending ActionSupport

andimplementing ModelDriven

Studentinstance created

public Student getModel(){

return student;}

getModel implemented

=

public String execute(){

studentService.saveStudent( student );

Studentobject populated with

dataandready touse

return SUCCESS;}

}Datawill beavailabe inview

Dont changeobject reference!


15/24

BasicvalidationaccessiblefromActionContext

TheDefaultWorkFlowInterceptorworksbehindthescenes

Separatesvalidation

logic

from

business

logic


16/24

public class CalculateAction extends ActionSupport{

private Integer numerator;

private Integer denominator;// set-methods

Class extending ActionSupport

Javabean properties

private Double result;// get-method

public void validate()Validate method containing logic

if ( denominator == null )

{addFieldError( denominator, Please enter a numerator );

}elseif ( denominator == 0 )

Storingerrors viamethods

provided byActionSupport

addFieldError( denominator, Divison by zero not allowed );}

}


Validation workflow separated

fromexecution

{result = // calculate somehow

}}


17/24

calculate.vmcalculate.vm

Inputresult isusedwhen

validation errors exist

< m >

#sform( "action=calculate" )#stextfield( "label=Numerator" "name=numerator" )#stextfield( "label=Denominator" "name=denominator" )

Validation error messages printed

forappropriate UI

tag in

view

#ssubmit( "value=Calculate" )#end


18/24

Separationlayerbetweensourcecodeandmessages

Builtupon

Java

resource

bundles,

which

will

be

found

in:

SamepackageandwithsamenameasActionclass

Classpathaftersettingstruts.custom.i18n.resources configproperty

..

LocaleaccessibleinJavacodethroughgetLocale()

propertiesofUItags


19/24

struts.xml configuration

salute=Bonjour!

i18n.propertiesini18nfolderon

classpath

Public class SaluteAction extends ActionSupport{

public String execute(){

Actionclass using getText(..)and

getLocale()

Locale locale = getLocale();return SUCCESS;

}}

#stext( "name=salute" )

Velocity template using text tag


20/24

HighleveltagAPIimplementedin:

JSP

Freemarker

Datatags

MovesdatabetweentheValueStackandtheview

Controltags

Altersthe

rendering

flow

of

the

view

UItags

ProvidesadvancedHTMLformcontrols


21/24

UsefultoapplydependencyinjectiontoaStruts2application

Struts2Springpluginisrequired(struts2springplugin)

.

Classattribute

in

Struts

2config

will

point

at

Spring

bean

identifiers

Approach2:Useautowiringbyname

Struts

2

will

instantiate

Actions

but

let

Spring

inject

beans

afterwards BeanidentifiersarematchedtosetmethodsinActions


22/24

Only the StudentService bean is

defined inthe configuration

public class SaveStudentAction extends ActionSupport{

Actionclass provides

StudentService property andset

methodpr vate tu ent erv ce stu ent erv ce;

public voic setStudentService( StudentService studentService ){

this.studentService = studentService;}

Name of setmethod ismatched

with Springbean identifiers

// Student properties and setters


{.

}

}


23/24

Struts2isbuiltupontheJavaServletspecificationwhichisbuiltuponHTTP

ru s so vesapp ca on eve rou newor no prov e y

theServletspecifiction

Validatingdata

Providinginternationalization

Renderingpresentationlayer

Makingcallstobusinesslayer


24/24

Brown,Davis,Stanlick:Struts2inAction

Velocityuserguide:

http://velocity.apache.org/engine/devel/user guide.html

Strutshomepage:

. .

Documents

Web Applications and Struts2