Grails - learning notes

Hello Grails!

Trailer.
Download and unpack Grails, set GRAILS_HOME environment variable and update PATH. It works

grails create-app mapp
cd mapp
grails create-domain-class mapp.site.Site
grails create-controller mapp.site.Site
Import project into Eclipse or NetBeans (Grails creates Eclipse project)
Add fields and toString() to model
Add dynamic scaffold property to controller (def scaffold=Site)
grails run-app
Run and show off dynamicity by adding fields to model, and index-method.

grails generate-all mapp.site.Site

Step back and explain:

• CoC: Show mapping url -> controller+view
  
• MVC: Jump to "Domain Model", "Controller", "GSP"
• Configuration: Set up database: store and update
  

Code a test

Why?
No configuration, zero overhead, immediate turnaround.
High-productivity web MVC framework for the Java platform

• CoC: easy to find your way to domain-objects, controllers, services, views
• Ready-to-use development environment (+test and production)
• Scaffolding (even dynamic): quick-start
  
• Familiar: On the shoulders of Java eco-system, Hibernate, Spring, Groovy, SiteMesh
  
• GORM: DAO-layer implemented by MOPing
• Good Ajax-support
• Small stuff: test support, generating (web-)services. flash-scope, Web-flow, filters
  
• Easily extensible, 312 Plugins at last count. Grails main function is plugin management.
  

Domain Model
You write POGOs, GORM provides DAO-functionality through mixins:

• get, list, save, delete
  
• findByName, findBy...And...

Validation provided.
Error container provided: siteInstance.errors
Command Object: domain object that is not persisted

Controllers
Scaffolding: CRUD generated. Provides a nice starting point.
Comment on first Controller generated:

• list(): where did Site.list() come from?
• list(): return statement optional.
  
• show(): what is flash-scope?
• show(): Model passed to view: Controller properties or returned map [key:value].
• edit(): same as show() but different view (by convention)
• update(): siteInstance.properties = params
  
• index(): will be default action if not overridden by eg. defaultAction = 'list';
  

View (GSP)
JSP works, but GSP takes advantage of Groovy, and is remarkably similar
GSP taglib similar to Struts2 + jstl

Services
Transactional boundaries, automagicaly injected.

Google app-engine
Fra http://grails.org/plugin/app-engine og http://www.morkeleb.com/tag/grails/
sørge for at domeneklasser ligger under en pakke
grails install-plugin app-engine
(valgte jpa)
grails install-plugin gorm-jpa
La til annotasjoner (@Entity)

grails app-engine run
grails set-version 1
grails app-engine package
(første gang $APPENGINE_HOME/bin/appcfg.sh update ./target/war)

grails app-engine deploy

Go 2 http://nerdetom.appspot.com/

IDE Support
Approaching acceptable, maybe good if my PC was working fine.
NetBeans: syntax colored, some autocomplete, access to grails-commands, direct junit debug
Eclipse: some syntax colored, some autocomplete, debug of junit-tests.
IDEA: supposedly best-of-breed.
Debugging: remote (grails-debug run-app) on port 5005

Recommended reading
http://grails.org
http://www.morkeleb.com/tag/grails/
Book: "The Definitive Guide To Grails" 2nd edition by Graeme Rocher and Jeff Brown. Comprehensive and readable guide, details Enterprise integration issues.
Mastering Grails on DeveloperWorks.
Agile Enterprise Development with Groovy and Grails: From JavaZone 09

Outro.