Grails(8)Guide Book Chapter 7 The Web Layer Groovy Server Pages

Grails(8)GuideBookChapter7TheWebLayerGroovyServerPages

7.1.13AsynchronousRequestProcessing

7.2GroovyServerPages(GSP)

7.2.1GSPBasics

GSPsupportstheusageof<%%>scriptletblockstoembedGroovycode.(discouraged)

<%=%>syntaxtooutputvalues.

7.2.1.1VariablesandScopes

<%now=newDate()%>

<%=now%>

Wedefineavariable,andusethatlaterinthesamepage.

application-Thejavax.servlet.ServletContextinstance

applicationContext-TheSpringApplicationContextinstance

flash-Theflashobject

grailsApplication-TheGrailsApplicationinstance

out-Theresponsewriterforwritingtotheoutputstream

params-Theparamsobjectforretrievingrequestparameters

request-TheHttpServletRequestinstance

response-TheHttpServletResponse

session-TheHttpSessioninstance

webRequest-TheGrailsWebRequestinstance

7.2.1.2LogicandIteration

<%[1,2,3,4].each{num->%>

<p><%="Hello${num}!"%></p>

<%}%>

<%if(params.hello=='true')%>

<%="hello!"%>

<%else%>

<%="Goodbye!"%>

IfoundthereisnoendtagintheGSPabove.Itwillconfuseme.

7.2.1.3PageDirectives

Theimportdirectiveletsusimportclassesintothepage.

<%@pageimport="java.awt.*"%>

<%@pagecontentType="text/json"%>

7.2.1.4Expressions

AGSPexpressionissimilartoaJSPELexpression.${expr}

Hello${params.name}

7.2.2GSPTags

7.2.2.1VariablesandScopes

<g:setvar="now"value="${newDate()}"/>//setjava.util.Dateinstance

<g:setvar="myHTML">

Somere-usablecodeon:${newDate()}

</g:set>//sethtmlcontent

<g:setvar="bookService"bean="bookService"/>//setservicebean

Therearefollowingscopes>

page-Scopedtothecurrentpage(default)

request-

flash

session

application

<g:setvar="now"value="${newDate()}"scope="request"/>

7.2.2.2LogicandIteration

<g:iftest="${session.role=='admin'}">

…snip...

</g:if>

<g:else>

…snip...

</g:else>

<g:eachin="${[1,2,3]}"var="num">

<p>Number${num}</p>

</g:each>

7.2.2.3SearchandFiltering

StephenKing'sBooks:

<g:findAllin="${books}"expr="it.author=='StephenKing'">

<p>Title:${it.title}</p>

</g:findAll>

TheexprattributecontainsaGroovyexpressionthatcanbeusedasafilter.

<g:grepin="${books}"filter="NonFictionBooks.class">

<p>Title:${it.title}</p>

</g:grep>

filterbyClass?

7.2.2.4LinksandResources

<g:linkaction="show"id="1">Book1</g:link>

<g:linkaction="show"id="${currentBook.id}">${currentBook.name}</g:link>

<g:linkcontroller="book">BookHome</g:link>

<g:linkcontroller="book"action="list">BookList</g:link>

<g:linkurl="[action:'list',controller:'book']">BookList</g:link>

<g:linkparams="[sort:'title',order:'sac',author:currentBook.author]"

action="list">BookList</g:link>

7.2.2.5FormsandFields

FormBasics

<g:formname="myForm"url="[controller:'book',action:'list']">…</g:form>

FormFields

textField

passwordField

checkBox

radio-Forinputfieldsoftype'hidden'

hiddenField

select

EachoftheseallowsGSPexpressionsforthevaluepart.

<g:textFieldname="username"value="${user.username}"/>

MultipleSubmitButtons

<g:actionSubmitvalue="Update"action="update"/>

7.2.2.6TagsasMethodCalls

7.2.3ViewsandTemplates

TemplateBasics

Grailsusestheconventionofplacinganunderscorebeforethenameofaviewtoidentifyitasatemplate.

grails-app/views/book/_bookTemplate.gsp

<divclass="book"id="${book?.id}">

<div>Title:${book?.title}</div>

<div>Author:${book?.author?.name}</div>

</div>

<g:rendertemplate="bookTempalte"model="[book:myBook]"/>

<g:rendertemplate="bookTemplate"var="book"collection="${bookList}"/>

SharedTemplates

Passmorepathtotherendertemplate

<g:rendertemplate="/shared/mySharedTemplate"/>

TheTemplateNamespace

TemplatesinControllersandTagLibraries

Wecanalsorendertemplatesfromcontrollersusingtherendercontrollermethod.ThisisusefulforAjaxapplications.

defbookData(){

defb=Book.get(params.id)

render(template:"bookTemplate",model:[book:b])//firstthebookisthenamein//template,secondbisthevariable.

}

Alternatively,moreclear

defbookData(){

defb=Book.get(params.id)

Stringcontent=g.render(template:"bookTemplate",model:[book:b])

rendercontent

}

7.2.4LayoutswithSitemesh

CreatingLayouts

GrailsleveragesSitemesh,adecoratorengine.Layoutsarelocatedinthegrails-app/views/layoutsdirectory.

<html>

<head>

<title><g:layoutTitledefault="Anexampledecorator"/></title>

<g:layoutHead/>

</head>

<bodyonload="${pageProperty(name:'body.onload')}">

<divclass="menu">…snip…</menu>

<divclass="body">

<g:layoutBody/>

</div>

</div>

</body>

</html>

Thekeyelementsareasfollow:

layoutTitle

layoutHead

layoutBody

TriggeringLayouts

Thereareafewwaystotriggeralayout.Thesimplestistoaddametatagtotheview:

<html>

<head>

<title>AnExamplePage</title>

<metaname="layout"content="main"/>

</head>

<body>Thisismycontent!</body>

</html>

Inthiscasealayoutcalledgrails-app/views/layouts/main.gsp

SpecifyingALayoutInAController

Anotherwaytospecifyalayoutistospecifythenameofthelayoutbyassigningavaluetothe"layout"propertyinacontroller.Forexample,

classBookController{

staticlayout='customer'

deflist(){…}

}

Thenthelayoutgrails-app/views/layouts/customer.gspwhichwillbeappliedtoallviewsthattheBookControllerdelegatesto.

staticlayout='custom/customer'

grails-app/views/layout/custom/customer.gsptemplate

LayoutbyConvention

layoutbyconventionmeansthat

classBookController{

deflist(){…}

}

grails-app/views/layouts/book.gspwillbeappliedtoallviewsthattheBookControllerdelegatesto.

Alternatively,wecancreatealayoutcalledgrails-app/views/layouts/book/list.gspwhichwillonlybeappliedtothelistactionwithintheBookController.

Theapplicationdefaultlayoutis

grails-app/views/layouts/application.gsp

ThisisconfiguredinConfig.groovy

grails.sitemesh.default.layout='myLayoutName'

InlineLayouts

<g:applyLayoutname="myLayout"template="bookTemplate"collection="${books}"/>

Server-SideIncludes

7.2.5StaticResources

7.2.5.1Includingresourcesusingtheresourcetags

Pullinginresourceswithr:require

Touseresources,wecanindicatewhichresourcemodulesitrequires.

<r:requiremodule="jquery"/>

<r:requiremodules="query,main,blueprint,charting"/>

Addingpage-specificJavaScriptcodewithr:script

<r:scriptdispostion="head">

window.alert('Thisisattheendof<head>');

</r:script>

Linkingtoimageswithr:img

<r:imguri="/images/logo.png"/>

7.2.5.2Otherresourcetags

7.2.5.3Declaringresources

7.2.5.6Debugging

7.2.8GSPDebugging

Viewingthegeneratedsourcecode

?showSource=true

7.3.6UsingJSPTagLibraries

<%@taglibprefix="fmt"uri="http://java.sun.com/jsp/jstl/fmt"%>

7.4.4MappingtoResponseCodes

staticmappings={

"403"(controller:"errors",action:"forbidden")

"404"(controller:"errors",action:"notFound")

"500"(controller:"errors",action:"serverError")

}

staticmappings={

"403"(view:"/errors/forbidden")

"404"(view:"/errors/notFound")

"500"(view:"/errors/serverError")

}

7.4.5MappingtoHTTPmethods

staticmappings={

"/product/$id"(controller:"product"){

action=[GET:"show",PUT:"update",DELETE:"delete",POST:"save"]

}

}

7.4.6MappingWildcards

staticmappings={

"/images/*.jpg"(controller:"image")

}

References:

http://grails.org/doc/latest/guide/index.html

http://grails.org/doc/latest/guide/theWebLayer.html#asynchronousRequestProcessing