JSP Velocity Freemarker comparison

JSP has been the De facto standard for Java and web development for years. JSP is one of the first popular dynamic web application frameworks. Since then as architecture models have evolved. PHP has taken a foothold in the simple dynamic web applications and large enterprise application with complex business logic has moved to MVC design using Java or .Net. Where does that leave JSP and how does it compare with Velocity and Freemarker?

JSPOverview

Originally,JavaServerPagesweredesignedtobeutilizedwithinaJ2EEwebcontainerthatwouldallowforfullapplicationdevelopment.OlderapplicationsweredesignedtobewrittentodirectlyaccesstheJSPfiles.ThisistheMVCmodel1architectureapproach.TheclientdirectlyreferencestheJSPpage,theJSPpagereferencesabeanwhichinturncanaccessdatabaseinformation.Withtoday'sstandards,however,itistypicallynotacceptabletoutilizeJSPasanindependentarchitecturesolution.Assoftwarearchitecturehasevolvedanddesignpatternshavechanged,itseemsthatthepurposesofJSPpageshavechangedaswell.

TheabilityofJSPtopermitscripting,tags,andhtmlcodemakesitaspowerfulasJavaitselfwiththecapabilitytobedirectlyrunasawebpage.Torebuttalthestrengthofthispoint,thisunrestrictedabilityofallowingsomanydifferentdevelopmenttechniquesissimplydangerous.ItbecomesdangeroustoboththeapplicationarchitectureandtotheaveragedeveloperasitisveryeasytointroduceinconsistencyindesignpatternsintotheJSP.ThecomplexityofJSPcangrowquicklyandfurtherdevelopmentorongoingmaintenancecouldsufferinbothtimeandcost.

AnexampleofabusiveJSPdevelopmentcanoccurwhenmixingdifferentJSPsyntax.UsinganparticulartaglibrarywithwithanexpressionorusingETLinsideandoutsideoftags.JSPScripletsareinviolationoftheMVCapproachwhenusingJSPasaviewcomponentwhichistheprimaryfunctionJSPpagesareusedtoday.

VeloctiyandFreemarkerOverview

VelocityandFreemarkeraretemplateenginesthatdefineatemplatelanguageinwhichtoparse.TheytakeJavaobjectsandmergethedatawiththetemplate.VelocityandFreemarkeraresosimilarIwillnotcompareonetotheother.Bothareactiveprojects.Velocityrecentlycameoutofitsshellafterafewslowyearsandhadsomereleasesin2007.Freemarkermayhaveafewbitmorefunctionalitythanvelocitybutisalsoabitmorecomplex.

JSPvsTemplateEngines

*CompileTime-JSPneedtobeprocessedandcompiledtobeforeitisexecuted.JSPfileisconvertedtoaJavafile.Itisthencompiledintoaclassfile.Bothvelocityandfreemarkerdonotneedcompiliation.Thisisespeciallybeneficialtoadeveloper.EverytimeadevelopermodifiesaJSPitisveryslowtorunitduetocompilation.TheVelocityengineisnamedVelocityforareason.

*LearningCurve-JSPisverylargewithmanytagdifferentlibraries.VelocityandFreemarkeraresimple.Theengineandcorefunctionalitycanbeunderstoodwithinamatterofhours.

*Readibility-JSPallowsfortaglibraries,scriplets,expressionlanguage,andothervarioustechniquesthatisrecognizedascode.Velocityusesashortlistofbuiltincommands.

*CommunityBase-ManydevelopersknowJSP.Itisaverycommonlanguagefordeveloperstolistasaskill.BothfreemarkerandvelocityhavealargeuserbasebutneitherisaslargeasJSP.ThisisbecauseJSPwasoriginallyusedasafullapplicationframeworkwhendeployedtoacompliantwebcontainer.

*Templatestructure-JSPallowsformanydifferenttypesofsyntax.Scriptingtechniquessuchasdeclarations,scriptlets,andexpressionsaswellasactionsandtags.Velocityusesa#commandforcommandsand$varforvariables.Freemarkeruses<#command>forcommandsand${var}forvariables.JSP2.0triestoappearastemplateenginewith${}tryingtoresembletemplatestyle

*CustomTools-JSPallowsforthecreationofJSPtaglibs.BothFreemarkerandVelocityallowtheutilizationofJSPtaglibsaswell.Freemarkerhasalotofextrabuiltinfunctionalityaswell.Velocityallowsthedevelopertocreatetheirowncustomtools.ThesetoolsarecreatedinJavaandutilizedasJavaobjectswithinthetemplate.

*Integration-MostofthemajorlibrariesanddevelopmenttoolsintegratewithJSP,VelocityandFreemarker.FrameworkssuchasSitemesh,Tiles,Struts,andSpringhavefunctionalityavailabletoutilizeall3technologies.

therearecoupleofthingswhereFreeMarkermightsuityoubetter:

1.Thisissubjective,buttheoverallsyntaxislessawkward.I’mawarethere’slotofsyntacicsugarinJSP2.0that’saimedathidingtheuglinessofdirectlyusingJSTLtagsforcontrolflowetc.butrememberthatFreeMarkerhashadaratherergonomicsyntaxfor“foreach”and“if”foryears.

2.Macros.Ifyouwanttohavereusabletemplatesnippets,youcanwritethemasmacrosandimportthem.AFAIK,inJSP2.0youfinallyhaveasortofmacros,butyouneedtodefineeachsnippetinitsownfile.Thisisnowhereaselegantasthefullnamespace/macrosolutioninFreeMarker.

3.Transforms.TransformsaretheequivalentofbodytagsinJSP,withasignificantdistinctionthatwhileJSPbodytagsfirstcachealloftheirbodyandonlyafterthatactonthem,FreeMarkertransformsarefullyoutput-driven,infacttheyareimplementedinternallyaschainsofjava.io.Writerobjects.Therefore,regardlessofhowmanytransformsyouhavenested,youcanstillhaveprogressivepagerendering(“can”becauseatransformcanchoosetocacheallofitsbodylikeaJSPbodytag,butisnotmandatedtodosoandcanprovideacleverimplementationthatallowsprogressiveprocessing).

4.Also,theusualargumentaboutusabilityoutsidetheHTTPprotocolstack.IfyoursystemdoesanytextoutputbesideHTTPresponses–i.e.sendsSMTPmail,youcanuseFreeMarkerforgeneratingmailmessagesfromtemplates,too,orforgeneratingarbitraryXML.ItevenhasdeclarativeXMLprocessingcapabilitieswhichmakeitpossibletouseitsimilartoXSLT,butsignificantlylesscomplex.Youcansimplifyyourprojectbyhavingonelanguageforallyourtextoutputgeneratingneeds.

5.Datamodelflexibility–ifyoulike,youcanimplementthedatamodelinterfacestonaturallyrepresentanyunderlyingdatamodel.I.e.wehaveawrapperforJythonobjectsthatprettyfaithfullyreflectsthelookandfeelofJythonobjectsinthetemplatesyntax.PeoplehavereportedprovidingasimilarbindingforJavaScriptetc.

There’salsolotsofgoodieslikeautomaticHTMLorXMLescapingofexpressions,convenientliteralsyntaxforlistsandmaps,etc.

Thismuchoffthetopofmyhead–it’sabitlatehere,soIcan’tthinkofanythingelseatthisverymoment.

Velocity'sSimplisticdesign

Ofthethreetechnologies,velocityisthesimplest.Ithasasmallamountofverypowerfulcommands.Syntaxisasfollows.

Displayvariablename

$var

Displayvariablename.Ifnullitdisplaysblank

$!var

Directives

#foreach($itemin$collection)itemis$item#end

#if($order.total==0)Nocharge#end

#parse("header.vm")

#macro

#include("disclaimer.txt")

#set($customer=${order.customer})

CodeComparisons

HereissomecodethatiswritteninJSP.Thisisthelogicthatwouldbeusedwhenprocessinganumbernamed"number"ispassedinasaparameter.

<%@pagelanguage="java"%>

<%@tagliburi="/WEB-INF/struts-logic.tld"prefix="logic"%>

<logic:equalparameter="number"value="7">

Youguessedright!Youwinahighspeedblender!

</logic:equal>

<logic:notEqualparameter="number"value="7">

<logic:lessThanparameter="number"value="7">

Alittlehigher...

</logic:lessThan>

<logic:greaterThanparameter="number"value="7">

Alittlelower...

</logic:greaterThan>

</logic:notEqual>

Andhereisthesamelogicwithinavelocitytemplate

#if($number==7)

Youguessedright!Youwinahighspeedblender!

#end

#if($number!=7)

#if($number<7)

Alittlehigher...

#elseif($number>7)

Alittlelower...

#end

Nowaanotherexamplewiththesametask.Createalistanddisplayit.FirstJSP.

<%@pagelanguage="java"%>

<%@tagliburi="/WEB-INF/struts-bean.tld"prefix="bean"%>

<%@tagliburi="/WEB-INF/struts-logic.tld"prefix="logic"%>

java.util.ArrayListlist=newjava.util.ArrayList();

list.add("First");

list.add("Second");

list.add("Third");

list.add("Fourth");

list.add("Fifth");

pageContext.setAttribute("list",list,PageContext.PAGE_SCOPE);

<logic:iterateid="myCollectionElement"name="list">

ElementValue:<bean:writename="myCollectionElement"/><br/>

</logic:iterate>

Andhereisthevelocityversion.

#set($list=["First","Second","Third","Fourth","Fifth"])

#foreach($itemin$list)

ElementValue:$item<br/>

#end

Conclusion

JSPhasprovideddeveloperswithaveryusefullibraryandtoolset.Ithasbeenaroundforalongtimeandtherearenosignsthatitsusersaredeclining.DuetoMVCstylearchitecture,serversideprocessingincludingbusinesslogicshouldnottakeplacewithintheviewcomponent.IdidnotgetintoVelocityvsFreemarkerdebatesincetheyareidenticalfromanarchitecturalstandpoint.Youcanmakethatdecisionbycomparingthetemplatelanguageitselfandchoosewhichisbettersuitedforyourneeds.WhendeterminingwhichtechnologytoutilizeIhopethatyoutaketimetoresearcheachtechnologyandusethisarticleasareference.

JSP Velocity Freemarker comparison

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