Slide 1: Rapid Web Application Development with Grails
Graeme Rocher
Managing Director Agilize it http://www.agilizeit.com
Session ID# BOF-2521
2006 JavaOneSM Conference | Session BOF-2521 |
Slide 2: Goal of this Talk
Rapid Web Application Development with Grails
Learn how to rapidly create web applications using the agile web application framework Grails
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Slide 3: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
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Slide 4: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
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Slide 5: Groovy & Grails
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Grails: MVC web framework inspired by:
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Convention over Configuration Don’t Repeat Yourself (DRY) Ruby on Rails Spring IoC, MVC and WebFlow Hibernate SiteMesh
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Built on solid foundations:
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Why Groovy?
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Meta-Programming Closure Support Syntactically Expressive
Java Integration
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Slide 6: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
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Slide 7: Getting Started
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Grails available from http://grails.org Stable & Development snapshots available Simple installation:
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Download & extract zip Set GRAILS_HOME variable Add $GRAILS_HOME\bin to PATH variable
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Run “grails create-app”
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Slide 8: Project Infrastructure
+ PROJECT_HOME Main Grails resources + grails-app + conf + controllers + domain + i18n + services Jar archive libraries + taglib + views Additional Spring configuration + lib + spring + hibernate Additional Hibernate mapping + src Java sources + web-app Web resources e.g. CSS, JavaScript etc.
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Slide 9: Command Line Targets
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Apache Ant bundled with Grails Many useful targets available:
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create-* (for creating Grails artifacts) generate-controller generate-views run-app test-app run-webtest
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Slide 10: The Data Source
// data source located in grails-app/conf Class ApplicationDataSource { @Property pooled = false @Property dbCreate = “create-drop” @Property @Property @Property @Property DB Auto creation with hbm2ddl url = “jdbc:hsqldb:mem:testDb” driverClassName = “org.hsqldb.jdbcDriver” username = “sa” password = “sa” Remaining connection settings
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Whether connection Pooling is enabled
}
Slide 11: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
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Slide 12: The Application Domain
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Domain classes hold state and implement behaviour They are linked together via relationships (e.g. one-to-many) In Java domain classes have traditionally been handled by Object-Relational Mapping (ORM) Grails provides simple ORM built on Hibernate
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Slide 13: Grails ORM (GORM)
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Extremely simple. No special class to extend or file to configure!
Each domain class has an ‘id’ and ‘version’
class ExpenseReport { @Property Long id @Property Long version
@Property relatesToMany = [items:ExpenseItem] @Property Set items @Property Date submissionDate @Property String employeeName }
Defines one-to-many relationship to ExpenseItem
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Slide 14: Grails ORM (GORM)
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We’ve got this far, so lets define the other side!
class ExpenseItem { @Property Long id @Property Long version
Defines the owning side of the relationship
@Property belongsTo = ExpenseReport @Property String type @Property Currency currency @Property Integer amount }
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Each property maps To a column
Slide 15: Grails Constraints
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Validation constraints can be defined using the ‘constraints’ property
class ExpenseItem { … @Property constraints = { type(inList:['travel', 'accomodation']) Each node relates to amount(range:1..999) a property } Ensures the ‘type’ property Is one of the values in the list } ‘amount’ must be
in a range greater than 0 but less than 1000
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Slide 16: Dynamic Methods & Properties
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Grails injects methods and properties into domain classes at runtime:
def r = ExpenseReport.findByEmployeeName('fred') def r = ExpenseReport .findBySubmissionDateGreaterThan(lastMonth) def reports = ExpenseReport.findAll() assert ! (new ExpenseItem().validate()) def er = new ExpenseReport(employeeName: 'Edgar') .save()
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Slide 17: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
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Slide 18: Controllers
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Controllers handle requests and prepare responses Response created by either delegating to a view or writing to the response A controller is a class containing closure properties that act on requests The convention used for the name of the controller and the actions within map to URIs.
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Slide 19: The Controller
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The controller and action name map to the URI: /expenseReport/list The name of the
class is the first token in the URI Each action is a closure property
class ExpenseReportController { @Property list = { [expenseReports : ExpenseReport.list()] } An optional model } is returned as a
map
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Slide 20: Data Binding & Flow Control
// save action @Property save = {
Dynamic get method Auto-type conversion To id type
def e = ExpenseItem.get(params.id) e.properties = params
Auto-type conversion if(e.save()){ redirect(action:show,id:e.id) from request parameters } else { Example flow control via render and redirect methods }
render( view: 'create', model:[expenseItem:e] ) }
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Slide 21: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
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Slide 22: Groovy Server Pages
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A view technology very similar to JSP, but with Groovy as the primary language More expressive and concise with support for embedded GStrings & Tags Layout support through integration with SiteMesh Ability to define dynamic tag libraries
Source: Please add the source of your data here
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Slide 23: A GSP Example
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The GSP for the list action is named according to convention: grails-app/views/expenseItem/list.gsp
References the model returned by the controller
<html> <body> <g:each in="${expenseItems}"> </g:each> </body> </html>
Embedded GString expressions
<p>${it.type} – amount: ${it.amount}</p>
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Slide 24: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Ajax Support Scaffolding Java Integration
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Slide 25: Dynamic Tag Libraries
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Easy definition of simple, logical and iterative The body argument tags:
The name of the tag is a closure that can be invoked
class ExpenseTagLib { @Property dateFormat = { attrs,body -> out << new SimpleDateFormat(attrs.format) .format(attrs.date) } }
The attributes are passed as a map
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Slide 26: Dynamic Tag Libraries
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Using the tag requires no imports or configuration and can be reloaded at runtime!:
Tag called by name <p>Submitted: with the “g:” prefix <g:dateFormat date="${report.submissionDate}" format="DD-MM-YYYY" /> </p> Tag can also be <p><input type="hidden" called as a regular name="submissionDate" method! value="${dateFormat( date:report.submissionDate, format:'DD-MM-YYYY')}" /> </p>
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Slide 27: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Ajax Support Scaffolding Java Integration
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Slide 28: AJAX Support
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Built in “adaptive” tag library for Ajax Supports Prototype, Rico, and Yahoo (Dojo coming soon) Tags for remote linking, asynchronous form submission etc. Dynamic “render” method available for rendering XML snippets, or partial templates Save/Reload and dynamic tag libraries make Ajax even easier
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Slide 29: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Scaffolding Ajax Support Java Integration
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Slide 30: DEMO
Scaffolding
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Slide 31: Agenda
Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Scaffolding Ajax Support Java Integration
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Slide 32: Java Integration
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Now for the important bit, with Groovy and Grails you can: Call any existing Java library seamlessly Deploy as a WAR onto any JEE application server Write your domain model in Java, mapped with Hibernate, and still use dynamic methods! Take advantage of Hibernate’s power by mapping onto legacy systems. Use Spring’s dependency injection to integrate Controllers with existing services
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Slide 33: DEMO
ECLIPSE INTEGRATION
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Slide 34: Summary
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With the advent on Web 2.0 agility is key Dynamic frameworks (Grails, Rails, Django etc.) provide this through quick iterative development with a clear productivity gain However, for large scale applications statictyping and IDE support is crucial Grails provides the ability to use a blended approach And most importantly it runs on the JVM!
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Slide 35: For More Information
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Groovy website – http://groovy.codehaus.org Grails website – http://grails.org Mailing lists – http://grails.org/Mailing+lists Graeme’s Blog – http://graemerocher.blogspot.com Upcoming books ‘The Definitive Guide to Grails’ by Apress and ‘Groovy in Action’ by Manning
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Slide 36: Q&A
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