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Learn how to swiftly create web applications with the agile framework Grails, inspired by Ruby on Rails, Spring, and Hibernate, featuring Groovy language support. Dive into MVC architecture, efficient Java integration, and dynamic method implementation.
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Rapid Web Application Development with Grails Graeme Rocher Managing DirectorAgilize ithttp://www.agilizeit.com Session ID# BOF-2521
Goal of this Talk Rapid Web Application Development with Grails Learn how to rapidly create web applications using the agile web application framework Grails
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
Groovy & Grails • Grails: MVC web framework inspired by: • Convention over Configuration • Don’t Repeat Yourself (DRY) • Ruby on Rails • Built on solid foundations: • Spring IoC, MVC and WebFlow • Hibernate • SiteMesh • Why Groovy? • Meta-Programming • Closure Support • Syntactically Expressive • Java Integration Source: Please add the source of your data here
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
Getting Started • Grails available from http://grails.org • Stable & Development snapshots available • Simple installation: • Download & extract zip • Set GRAILS_HOME variable • Add $GRAILS_HOME\bin to PATH variable • Run “grails create-app” Source: Please add the source of your data here
Project Infrastructure • + PROJECT_HOME • + grails-app • + conf • + controllers • + domain • + i18n • + services • + taglib • + views • + lib • + spring • + hibernate • + src • + web-app Main Grails resources Jar archive libraries Additional Spring configuration Additional Hibernate mapping Java sources Web resources e.g. CSS, JavaScript etc.
Command Line Targets • Apache Ant bundled with Grails • Many useful targets available: • create-* (for creating Grails artifacts) • generate-controller • generate-views • run-app • test-app • run-webtest Source: Please add the source of your data here
The Data Source // data source located in grails-app/conf Class ApplicationDataSource { @Property pooled = false @Property dbCreate = “create-drop” @Property url = “jdbc:hsqldb:mem:testDb” @Property driverClassName = “org.hsqldb.jdbcDriver” @Property username = “sa” @Property password = “sa” } Whether connection Pooling is enabled DB Auto creation with hbm2ddl Remaining connection settings
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
The Application Domain • 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 Source: Please add the source of your data here
Grails ORM (GORM) • Extremely simple. No special class to extend or file to configure! class ExpenseReport { @Property Long id @Property Long version @Property relatesToMany = [items:ExpenseItem] @Property Set items @Property Date submissionDate @Property String employeeName } Each domain class has an ‘id’ and ‘version’ Defines one-to-many relationship to ExpenseItem
Grails ORM (GORM) • We’ve got this far, so lets define the other side! class ExpenseItem { @Property Long id @Property Long version @Property belongsTo = ExpenseReport @Property String type @Property Currency currency @Property Integer amount } Defines the owning side of the relationship Each property maps To a column
Grails Constraints • Validation constraints can be defined using the ‘constraints’ property class ExpenseItem { … @Property constraints = { type(inList:['travel', 'accomodation']) amount(range:1..999) } } Each node relates to 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
Dynamic Methods & Properties • 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()
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
Controllers • 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. Source: Please add the source of your data here
The Controller • The controller and action name map to the URI: /expenseReport/list class ExpenseReportController { @Property list = { [expenseReports : ExpenseReport.list()] } } The name of the class is the first token in the URI Each action is a closure property An optional model is returned as a map
Data Binding & Flow Control Dynamic get method Auto-type conversion To id type // save action @Property save = { def e = ExpenseItem.get(params.id) e.properties = params if(e.save()){ redirect(action:show,id:e.id) } else { render( view: 'create', model:[expenseItem:e] ) } } Auto-type conversion from request parameters Example flow control via render and redirect methods
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration
Groovy Server Pages • 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
A GSP Example • The GSP for the list action is named according to convention: grails-app/views/expenseItem/list.gsp <html> <body> <g:each in="${expenseItems}"> <p>${it.type} – amount: ${it.amount}</p> </g:each> </body> </html> References the model returned by the controller Embedded GString expressions
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Ajax Support Scaffolding Java Integration
Dynamic Tag Libraries • Easy definition of simple, logical and iterative tags: class ExpenseTagLib { @Property dateFormat = { attrs,body -> out << new SimpleDateFormat(attrs.format) .format(attrs.date) } } The body argument is a closure that can be invoked The name of the tag The attributes are passed as a map
Dynamic Tag Libraries • Using the tag requires no imports or configuration and can be reloaded at runtime!: <p>Submitted: <g:dateFormatdate="${report.submissionDate}" format="DD-MM-YYYY" /> </p> <p><input type="hidden" name="submissionDate" value="${dateFormat( date:report.submissionDate, format:'DD-MM-YYYY')}" /> </p> Tag called by name with the “g:” prefix Tag can also be called as a regular method!
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Ajax Support Scaffolding Java Integration
AJAX Support • 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
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Scaffolding Ajax Support Java Integration
DEMO • Scaffolding
Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Scaffolding Ajax Support Java Integration
Java Integration • 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 stilluse dynamic methods! • Take advantage of Hibernate’s power by mapping onto legacy systems. • Use Spring’s dependency injection to integrate Controllers with existing services
DEMO • ECLIPSE INTEGRATION
Summary 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 static-typing and IDE support is crucial Grails provides the ability to use a blended approach And most importantly it runs on the JVM!
For More Information 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