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Rapid Web Application Development with Grails

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

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  1. Rapid Web Application Development with Grails Graeme Rocher Managing DirectorAgilize ithttp://www.agilizeit.com Session ID# BOF-2521

  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

  3. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration

  4. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration

  5. 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

  6. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration

  7. 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

  8. 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.

  9. 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

  10. 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

  11. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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()

  17. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration

  18. 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

  19. 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

  20. 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

  21. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages (GSP) Tag Libraries Ajax Support Scaffolding Java Integration

  22. 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

  23. 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

  24. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Ajax Support Scaffolding Java Integration

  25. 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

  26. 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!

  27. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Ajax Support Scaffolding Java Integration

  28. 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

  29. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Scaffolding Ajax Support Java Integration

  30. DEMO • Scaffolding

  31. Agenda Groovy & Grails Getting Started The Application Domain Controllers Groovy Servers Pages Tag Libraries Scaffolding Ajax Support Java Integration

  32. 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

  33. DEMO • ECLIPSE INTEGRATION

  34. 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!

  35. 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

  36. Q&A

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