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Introduction to Grails

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Presentation on theme: "Introduction to Grails"— Presentation transcript:

1 Introduction to Grails
by Jason McDonald Java Users Group Charleston, SC June 25, 2008

2 Getting Started

3 Grails Basics Open Source Fully integrated with Java Groovy based
Uses ANTLR to compile Groovy down to JVM compatible bytecode Predicated on DRY principle

4 Underlying Technologies
Spring Hibernate Log4J Junit Quartz Ant

5 Native Support HSQL MySQL Servlet container servers AJAX and DHTML
Jetty Tomcat AJAX and DHTML Dojo Prototype Yahoo!

6 Installation Visit http://www.grails.org Download and extract files
Create GRAILS_HOME environment variable Add %GRAILS_HOME% to PATH environment variable That’s it!

7 Grails Structure

8 Goovy Roots Built on top of Java Very similar syntax to java
Supports closures Method returns can be slightly different Case sensitive No semi-colons needed All classes end in .groovy

9 Conditional Environments
Environment conditionals allow for variations for a specific environment Database Initialization options More Three environment choices Development Testing Production

10 Script Based Code Generation
grails create-app [app name] grails create-controller [controller name] grails create-domain-class [class name] grails create-service [service name] grails create-unit-test [test name] grails create-tag-lib [taglib name] grails generate-all [class name] grails generate-views [class name]

11 Building, Deploying, and Managing
grails clean grails compile grails console grails doc grails install-plugin grails run-app grails war

12 Important Files conf/DataSource.groovy conf/UrlMapping.groovy
Database connections conf/UrlMapping.groovy Routing conf/BootStrap.groovy Bootstrap file conf/Config.groovy Configurations (MIME mappings, more…)

13 Routing Route rules found in conf/UrlMapping.groovy Default route:
application/controller/action/id[?params] Additional rules and restrictions can be applied here static mappings = { "/product/$id?"(controller:"product"){ action = [GET:"show", PUT:"update", DELETE:"delete", POST:"save"] } }

14 Databases db configuration is in conf/DataSource.groovy
Can define at environment level or global level Defaults to HSQL Change to MySQL by: Dropping MySQL connector in the lib Changing DataSource.groovy to point at MySQL

15 Database Create Scheme
dbCreate create-drop: creates tables on startup and drops them on shutdown (DEV) create: creates tables on startup, deletes data on shutdown (DEV, TEST) update – creates tables on startup, saves data between restarts (TEST, PROD)

16 Grails MVC

17 MVC Framework Standard MVC implementation Sits on top of Spring MVC
Reduces repetition of XML developers must maintain Gives access to Spring DSL

18 Views Groovy Server Pages GSP extension Based on JSP pages Use
Tag libraries Expressions similar to JSP EL but allows any expression within ${…}

19 Tag Libraries Ordering and sorting <g:sortableColumn property="releaseDate" defaultOrder="desc" title="Release Date" titleKey="book.releaseDate" /> Form display <g:form name="myForm" action="myaction" id="1"> <g:passwordField name="myPasswordField“ value="${myPassword}" /> ... </g:form> Formatting <g:formatDate format="yyyy-MM-dd" date="${date}"/>

20 Custom Tag Libraries Custom tag libraries are just groovy classes that end with TagLib Defaults to ‘g’ namespaces unless declared Closure defines actual tag: class FormattingTagLib { static namespace = ‘fmt’ def dateFormat = { attrs -> out << new java.text.SimpleDateFormat( ‘dd-MM-yyyy’).format(attrs.date) } } <fmt:dateFormat date=‘${plan.effDate}’ />

21 Internationalization Support
Based on Java i18n specifications Define properties files with language specific entries Views can read i18n entries with a tag: <g:message code=‘my.message’ args=‘${[‘One’, ‘Two’]}’/> Tag libraries can read entries with code: g.message(code: ‘my.message’, args: [‘One’, ‘Two’])

22 Models POGOs Fields default to private
Getters and setters provided automatically Must use wrapper objects – no primitives (1.5?) Field validation defined within: static constraints = { date(nullable: false) } Can define custom messages using convention: className.propertyName.constraint = ‘’Err msg’’ Automatic parameter mapping from view book.properties = params

23 GORM Grails Object Relational Mapping Uses Hibernate3
Dynamic methods for finding Book.findByTitle(“The Dark Tower“) Book.findByTitleAndAuthor(“The Dark Tower”, “Stephen King” Book.findByTitle(“Christine”, [sort: ‘edition’, order: ‘asc’] ) Relational mapping defined within One to many: static hasMany = [ attendances:Attendance ] One to one: Attendance attendance

24 GORM Caching Provides the same caching mechanisms that can be found with Hibernate3 Updates to DataSource.groovy can toggle caching: hibernate { cache.use_second_level_cache = true cache.use_query_cache = true cache.provider_class = ‘org.hibernate.cache.EhCacheProvider’ }

25 Controllers House actions (methods) that respond to a request
Actions should map to GSP of same name index is the default action Can define the method each action is allowed: def allowedMethods = [save:'POST', update:'POST'] GET is the default Auto scaffolding sets up CRUD without files def scaffold = true // In Controller class

26 Action Responses All actions respond in one of three ways: redirect
Equivalent ot response.sendRedirect Can specify actions, controller, params, and more return Returns a value and calls a GSP of the same name (action method ‘go’ will forward to go.gsp) render Calls a GSP by name Has the ability to pass arguments

27 Grails in Action

28 Web Services REST SOAP Provide RESTful mappings in UrlMappings.groovy
Implement controller to accept and return marshalled data SOAP Supported through XFire plug-in Simply expose a service: static expose = [‘xfire’]

29 Testing Test framework based on JUnit Unit tests Integration tests
By convention uses mock objects Integration tests By convention use real objects Functional tests Supports Canoo WebTest integration

30 Running the Application
Bootstrapping data Allows for initialization and test data Jetty Server Specify port and environment on command line grails dev –Dserver.port=9999 run-app Tomcat As war Exploded

31 The Example

32 Requirements Application needs to:
Store meetings, people, and which meetings each person attends People should store first and last name Meetings should store date and subject of meeting Must have full CRUD capability Must be web based Must be able to integrate with Java environments (to meet future integration needs)

33 Open Discussion


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