Spring Northwest Usergroup Grails Presentation

Grails Presentation
Adam Evans
(http://www.ctisn.com)

What is Grails?
Rapid development framework
Convention over configuration
Built on proven technologies
Spring IoC
Spring MVC
Hibernate
Sitemesh
Uses groovy

What is Groovy?
A scripting language which runs on the JVM
Groovy Objects extend java.lang.Object
Seamless Java integration
Designed for the Java developer
Linear learning curve
Familiar syntax

A Java Class

And A Groovy Example

What's The Difference
NONE!
Groovy lets you use Java code in your groovy classes / scripts
We can make this groovier

A Groovy Example V2
No constructor – groovy allows you to pass in a map to set variables
Closures (the each function)
Null safe operations '?'
Extends standard JDK classes objects (the each function)
Typing optional – def keyword

Groovy
Allows you to use Java + Static typing when necessary
Adds additional functionality to standard JDK classes
Closures
MOP Meta Object Protocol
Java like syntax
Linear learning curve, you can start with Java and re-factor to make it groovier

Grails
Uses best practices with the power of Groovy to make a rapid development environment built on proven technologies you already know

Grails Cont
Provides a view layer (GSP's + Sitemesh)
Service layer (Service spring managed beans)
Repository (GORM, Grails object relational mapping...hibernate abstraction)
Unit / integration tests a key feature
The grails app structure

Grails Plugins
Provide a full slice of the application
Views
Controllers
Domain objects
Sessions
Scripts
Allow to make a application modular, great for teams working on feature sets and to reuse ability

Demo
Lets take a look at how easy it is to create a grails application and integrate spring libraries
We'll create a basic application to search twitter using the api, cache and display the results

Demo (contd)
Create the application, type 'grails create-app twitter-search' from the command line
We now have a fully functional web application, this can be run using 'grails run-app'

Demo (contd)
Create a service bean to query twitter. 'grails create-service com.demo.TwitterService'

Demo (contd)
Create a controller to query the service 'grails create-controller com.demo.TwitterSearch'
Notes:
1) Spring injects the TwitterService class based on the variable name
2) Controller actions are defined as groovy closures. We return
a map to the view. By convention the view will be under
'grails-app/views/${controller}/${action}‘ Iefor the above:
'grails-app/views/twitterSearch/search.gsp'

Demo (cont)
Create the view 'grails-app/views/twitterSearch/seach.gsp'
Note: the layout meta tag, this tells sitemesh to decorate the page using the
'grails-app/layouts/main.gsp' template

Complete
We now have a basic web application displaying results from the twitter api

Demo (cont)
Run 'grails-stats'
18 lines of code !

Integrating with Spring
We've not interacted with Spring directly so far
Grails has taken over in the background configuring the view resolver, url mappings / controllers for Spring MVN, injecting session beans

Spring In Grails
We'll look at making further use of Spring in Grails by using Spring AOP to cache the search results

Spring AOP In Grails
1) We place the required lib directory
aspectjrt.jar (v1.5+)
aspectjweaver.jar (v1.5+)
2) Create the spring config xml file 'grails-app/conf/resources.xml'
Note: As of grails 1.2 the component-scan will not be needed as grails supports the
@Component annotation by default

Create a Annotation
We create a Cacheable annotation under src/java.

We create a Aspect
With the above, any method with the annotation @Cacheable will be handled by the aroundAdvice method. For now we just called proceed() so the method We are intercepting is executed and
we return the value

Trivial Caching
As we apply 'around' advice to our method it is trivial to cache.
Check if we have a cached value
If not execute method and store result
else load cached item
Return result
For this example grails comes with the oscache libs already so I'll use that for the caching

Trivial Caching (cont)

Trivial Caching (cont)
Below is the function we use to generate the cache key based on method name / arguments

Conclusion
We've seen how Grails integrates with
Java
Spring
The rapidness of creating a application
If you have a spring application already you can import your spring beans into Grails
Boilerplate code has gone, no more days lost setting up new projects writing masses of XML

Points not Discussed
Scaffolding
Grails attempts to create basic views of your domain to get you started
GORM

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Spring Northwest Usergroup Grails Presentation

by ajevans on Dec 02, 2009

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Spring Northwest Usergroup Grails Presentation — Presentation Transcript