The document discusses Groovy and Grails. Groovy is a dynamic language for the JVM that is inspired by languages like Python and Ruby. It allows seamless integration with Java classes and libraries. Grails is a web framework for Groovy that is inspired by Ruby on Rails. It uses Spring MVC, Hibernate, and other technologies to provide features like auto-generation of code and integration with databases. The document provides examples of using closures, dynamic methods, lists, and maps in Groovy and generating applications using Grails.

1. Groovy and Grails
Prabhu
prabhu@prabhu-s.com

2. Groovy
• is an agile and dynamic language for JVM
• Features inspired from Python, Ruby …
• Seamless integration with all existing
Java classes and libraries.
• Groovysh and GroovyConsole
• Can run on .Net 2.0 using IKVM
• Latest version 1.5
• http://groovy.codehaus.org

3. Features
• Closures
• Dynamic Methods
• List & Maps
• Better XML/Swing Capabilities

4. Closure
• Statements enclosed within curly braces
“{}“
• Can be passed around like variables
• Return value either using return
keyword or the value of last executed
statement.

5. Closure (Contd)
square = { it * it }
square (4)
Output = 16
“it” implicit parameter representing the
passed value.

6. Closure (Contd)
square {
it * it
return 3
}
square (4)
Output = 3 (Since there is an explicit
return statement!)

7. Closure (Contd)
square = { param1 ->
param1 * param1
}
square (3)
Output = 9
Param1 – Named parameter

8. Factorial using closures
fact = 1 fact = 1
for (i in 2..5) { (2..5).each {
number ->
fact *= i
fact *= number
} }
print fact print fact
// (2..5) = Range

9. Factorial again!
fact = 1
2.upto(5) { num ->
fact *= num
}
print fact
// Numbers are treated as object.
• upto method generates all number objects
• To each object, the closure gets passed
around!

10. Generic Factorial
fact = 1
fun = { n->
2.upto(n) { num ->
fact *= num
}
}
fun(5)
print fact

11. Dynamic methods
class webcamp {
def haveTea() {
println quot;Time for teaquot;
}
}
camp = new webcamp()
camp.haveTea()

12. Dynamic methods (Contd)
• Add a new method “haveSamosa”
class webcamp {
def haveTea() {
println quot;Time for tea“
}
}
camp = new webcamp()
camp.haveTea()
webcamp.metaClass.haveSamosa = { ->
println quot;Have Samosa alsoquot;
}
camp = new webcamp() // Create a fresh object since the class has
changed!
camp.haveSamosa()

13. Lists and Maps
• Like python
List = [2,3,4]
Map = [„a‟ : 2, „b‟ : new Date()]

14. Grails
• Web Framework inspired by RoR
• Latest version is 1.0.1.
– The one in the DVD is 1.0 and doesn‟t run cleanly in
windows!
• Grails = Spring MVC 2.5.1 + Hibernate 3 +
SiteMesh 2.3
• Newbie‟s are unaware that Grails is full and full
Spring!
• Provides several commands to auto generate
code.
• Comes bundled with HSQLDB.

15. Create your first app
• Set environmental variables
GRAILS_HOME and PATH
• grails create-app firstapp

16. Directory Structure
Controllers
Domain
Views
Sources
Test cases
J2EE Web Appln.

17. First app Demo
• grails create-domain-class <name>
• grails create-controller <name>
• grails run-app (Starts inbuilt Jetty 6.1.4
server)
• Visit http://localhost:8080/firstapp
• Demo

18. Features
• Both gsp and jsp are supported.
• Specify constraints
static constraints = {
username (minLength : 3, maxLength: 8, blank:false)
password(minLength : 5, maxLength:9, blank:false)
}
• Specify Optional fields
static optionals = [“middle_name”, “addr2”]

19. Features (Contd)
• Dynamic finder methods
def search = {
render(view : „list‟,
model : [userList :
User.findAllByUsernameLike (
„%‟ + params.username + „%‟)
]
)
}
• User.findAllByUsernameLikeAndPassword
Like

20. Features (Contd)
• Create Advanced Search criteria using
Hibernate Criteria Builder.
def criteria = User.createCriteria() // Dynamic method
def results = criteria {
and (
like („username‟ , „%‟ + params.username + „%‟)
le(„age‟, params.age)
)
}
Render(view:‟list‟, model:[userList : results])

21. Features (Contd)
• Flash scope - Data will be stored as
name-value pairs for current request
and the next request.
• Create custom tags just by creating a
new file in grails-
app/taglib/<name>TagLib.groovy

22. Features (Contd)
• AJAX Support
– Supports prototype, YUI, DOJO
– Use render method in your groovy code to
render text, HTML, JSON or OpenRico
Response XMLs
• Plays nicely with flex
– Simply add this
static expose = [“flex-remoting”]
– Automatic flex based CRUD generation and
Domain class to AS3 compilation coming up!

23. Features (Contd)
• Plays nicely with EJB
– http://www.infoq.com/articles/grails-ejb-
tutorial
• Has lots of plugins already!
– grails install-plugin <name>
– grails create-plugin <name>

24. Scalability
• Thanks to Spring and Hibernate, Grails
is highly scalable and already enterprise
ready!

25. RoR Competition?
• No.
– Instead going to compete with Java based
frameworks like struts 2, JSF, Seam.

26. Should I learn?
• If you are a Java guy, then yes.
• Companies like Oracle have already
started showing full support!

27. Thanks
Q&A