Download pdf - Grails Overview

 WhatisGrailsandwhyshouldIcare?

  BuildingonJava’sstrengths

  TheGroovylanguage

  AtourofGrails

  AncillarytoolsusefulinGrails©2009DevJam‐Allrightsreserved.

 Webapplicationdevelopmentenvironment  BuiltontheJavaPlatform  Groovyastheprimarylanguage

  JavacanalsobeusedandintermixedwithGroovyseamlessly

  FavorsConventionoverConfiguration  SimilarinspirittoRubyonRails

©2009DevJam‐Allrightsreserved.

  Javawebdevelopmentcanbetedious  TheJVM,classlibraries,andframeworksaretherealstrengthoftheJavaPlatform

  GroovyisanexcellentdynamiclanguagefortheJVM  CompilestoJavabytecode(.classfiles)

  Favorconventionoverconfiguration  Grailsisanopinionatedframework

  Enhancesproductivity©2009DevJam‐Allrightsreserved.

  BuiltontopoftheJavaVirtualMachine Maturity  Optimizationandperformance  Runtimefamiliarity

  IntegrationwithJavaapplications  GroovyclassesareJavaclasses  ReusewhatworksfromtraditionalJavastack▪  JavaEE:ServletAPI,JDBC,JMS▪  Hibernate,SpringFramework,SpringMVC,SiteMesh



  Hibernate  Object/relationalmapping(ORM)

  SpringFramework  Dependencyinjectionservices  Applicationlifecyclefacilities

  SpringMVC Webframework

  SiteMesh  Userinterfacelayoutandthemingfacilities


  Grailsconventiondictates… Wherecomponentsresideintheapplication  Howthecomponentisnamed  Howthecomponentiswiredandcollaborateswithotherapplicationcomponents

  Howapplicationscanbeextendedthroughtheuseofthird‐partyplugins


  Standardizedconfiguration  Log4j,databasedatasources  Autowiringanddependencyinjectionofcomponents

  Standardizedbuild  Gantscripts

  Standardizeddomainmodel  GORMfacilitiesinjectedintodomainobjects

  Standardizedservices  Automatictransactionsupport


  FeaturesinspiredfromPython,Ruby,andSmalltalk

  CanbecompiledtoJavabytecode  GroovyclassesareJavaclasses

  GroovycanseamlesslyuseJavaclasses  JavacanseamlesslyuseGroovyclasses*

  Lotsofnewlanguagesfeatures  GPath,GString,internaliterators,closures,Meta‐ObjectProtocol(MOP),andmanyothers


  JDBCisusedforcommunicatingwithdatabases

  HSQLDB:defaultdatasource  DataSource.groovy

  ConfigurationofDataSourcesforallyourenvironments

  Easytoswitchtoadifferentdatabase,evenacrossdifferentdeployments


  DomainclassesarecentraltoaGrailsapplication

  Locatedingrails‐app/domain  Allattributespersistentunlessmarkedinthetransientsproperty

  Nogettersandsettersnecessary  Validators:specifiedinconstraintsproperty  GORMmapping:customizedinthemappingproperty


  GrailsObjectRelationalMapping  LeveragesHibernate

  Automaticallymapsdomainobjectstodatabase

  Providesqueryandupdatefacilities  Findingobjectsinthepersistencestore(findBy…methods).

  Persistencelifecyclemethods(save,update,delete).

  CriteriaandHQLqueryfacilities.©2009DevJam‐Allrightsreserved.

  Noneedtoextendacommonpersistentbaseclass  GrailsinjectsGORMfunctionalityintoobjectsatrun‐time.

  Declarepropertiesforyourdomainobjects  Theidorversionpropertiesareinjectedautomatically.

  Allpropertiesarenotnull/requiredbydefault


  Associations  One‐to‐one,one‐to‐many,many‐to‐many  Uni‐directionalandbi‐directional  OwnersdefinedbyusingbelongsToproperty

  Inheritancehierarchies  Table‐per‐hierarchy:Allclassesmaptoasingletable

  Table‐per‐subclass:EachclassmapstoitsowntableandJOINsareused


  Retrievingobjects  get(), getAll(), read()

  Listingobjects  list(), listOrderBy*() methods  order, sort, offset, andmaxnamedarguments

  Dynamicfinders(findBy*())  Usepropertynamesoftheclass  Supportformanyexpressionsinfindermethod


  BuiltonHibernate’sCriteriaAPI  Groovybuilderisusedtobuildupthecriteria

  Hierarchyofmethodcallsandclosuresforbuildingtree‐likestructures

  EachdomainclasshasacreateCriteria()method  Callget,list,scroll,orcountoncriteria  Thecriteriabuilderisusedtorestrictthequery

  Supportsassociationsandprojections©2009DevJam‐Allrightsreserved.

  SupportforHibernateQueryLanguage  find(hql), findAll(hql), andexecuteQuery(hql) forqueries

  executeUpdate(hql)forDML‐styleopera3ons(setsofupdatesordeletes)

  Supportforpositionalandnamedparameters


  HandlesHTTPrequestsanddeterminesrenderingresponsibility

 Manyobjectsareavailabletoyourcontrollerclosures  log,params,request,response,session,servletContext,flash

  Interceptorsonacontroller  beforeInterceptorandafterInterceptorclosures


  Fileupload/multipartrequests  Automaticbindingtodomainobjects  <g:uploadForm />

  Binaryresponsewriting  response.outputStream  response.contentType   Overloaded<<operatortoappendcontent

  RequestInputStreamreading  def incomingText = request.inputStream.text


  BuiltuponSpring’svalidationframework  org.springframework.validationpackage

  Domainobjectshavevalidationbakedin  save()andvalidate()methodstriggervalidation  Validationerrorspopulateerrorspropertyondomainobject

  Errors  Interrogatethedomainobjectinstance  hasErrors()methodanderrorsproperty


  SimilartoJSPs  UtilizesGPathandGStringsandothercoolGroovylanguagefeatures

  AutomaticdiscoveryofGrailstaglibs  Supportfortemplates

  Smallsnippetsofviewcodethatotherviewscanuse

  UsefulforAJAXresponses


  Grailsshipswithastandardsetoftaglibs  Iteration,filtering,switching,logicaltaglibs  HTMLmarkupcreation:links,forms,formfields,datepicker

  Validationerrorcheckingandrendering  Paginatingviews  Viewtemplaterendering(reusablesub‐views)

  Customtaglibsareeasy  GroovyclasswithaTagLibsuffixandresidesingrails‐app/taglibdirectory


  GrailsusesPrototypelibrarybydefault   EasilychangedtoanotherJavaScriptproviderthroughGrailspluginsystem

  GrailstaglibsinsulateyoufromtherawJavaScript  Remotelinks,remoteforms,remoteformfields,beforeandaftercallbacks,eventhandling,effects,animations


  Grailshasbuilt‐insupportformanagingmessagebundles,locales

 Messagefilesaremanagedinthegrails‐app/i18ndirectory

  Grailstaglibcanbeusedtoretrievemessagesfrommessagebundles  Supportsparameterizedmessaging

  SupportforspecialURLmappingstosupportencodinglocaleinformationintheURI


  Allowsforcentralizationofapplicationbehavior  Necessarycomponentinanynon‐trivialGrailsapplication

  Transactionalbydefault,setthroughthetransactionalproperty

  Usetheexposepropertytoexposeaserviceviaremotingtootherprocesses  Usewithvariousremotingplugins


  ReflectionandtheGroovyMetaClassareusedtoscaffoldCRUDfunctionality

  Enableinthecontrollerclass…

class UserController {

def scaffold = User … }


  Extensionmechanismforintegratingthird‐partyfunctionality

  About80orsopluginstodayandmanymorecomingonboard  AJAX,JavaScript,Flex/Flash,UIwidgets  Security,Crypto,CAPTCHA,CAS  Databasemigration,codecoverage,functionaltesting

 Manyothers…findatgrails.org/plugin/list©2009DevJam‐Allrightsreserved.

  SwingGUIconsole  AllowsexecutionofarbitraryGroovystatements

  YourGrailsdomainmodelisaccessibleinthisenvironment  GORMfacilitiesareavailable  Greatwaytotinkerandplaywithyourdomainobjectmodel


  Eclipse  Pluginavailable,butthestoryisnotgoodatthemoment

  NetBeans  GroovyandGrailssupportinversion6.5

  IntelliJIDEA  JetGroovypluginbyJetBrainsoffersgoodsupportforGrails

  Seemstobetheleaderatthemoment


  TakeGrailsonatestdrive!  grails.org

  Books  GroovyinAction  TheDefinitiveGuidetoGrails,SecondEdition  BeginningGroovyandGrails  GrailsinAction  GroovyandGrailsRecipes  GrailsPersistencewithGORMandGSQL


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