This document introduces Grails, a web framework based on Java, Groovy, Spring, and GORM. It discusses how Grails enables rapid development through scaffolding and plugins, supports modern browsers, and allows rendering objects to JSON and XML. The document also provides an overview of Groovy and its similarities to Java, and demonstrates Grails through examples of parallel computing with GPars and calling Clojure code from Grails services.

1. Why
Grails?
Yiguang
Hu

2. What
is
Grails?
• Grails
is
a
web
framework
based
on
– JAVA,
GROOVY,
Spring,
GORM
• Scaffolding!
• Plugin
everything!!!
– GWT,
DWR,
YUI,
ACEGI,
Google
AppEngine,
Google
Wave,
COMET,
JQuery,
Clojure,
Scala,
JSF,
Struts…
• Support
all
modern
browsers
automaRcally
• Render
object
to
JSON,
XML
free!
• MVC+IOC(services)+plugin

3. Why
Grails?
• Rapid
– Have
your
next
Web
2.0
project
done
in
weeks
instead
of
months.
Grails
delivers
a
new
age
of
Java
web
applicaRon
producRvity.
• Dynamic
– Get
instant
feedback,
see
instant
results.
Grails
is
the
premier
dynamic
language
web
framework
for
the
JVM.
• Robust
– Powered
by
Spring,
Grails
out
performs
the
compeRRon.
Dynamic,
agile
web
development
without
compromises.
• Proven
Technologies:
JAVA(Groovy),
Spring,
GORM

4. What
is
Groovy?
• Groovy
=
– JAVA+Dynamic
Typing+Closure+
DSL,
GPars,Griffon….
• Runs
on
JVM
• 0
Learning
curve
for
Java
programmer

5. Success
Stories
• The
Sites
I
personally
involved:
– Worthpoint.com
(80
million
records)
– Gsword:
h_p://www.ccimweb.org/gsword
• Web
2.0.
Highly
interacRve.
• Done
in
two
days!
– Others

6. Demo
• Install
java,
groovy,
grails
• grails
create-­‐app
interop
– Goto
dir
interop
and
see
the
dires/files
created
• Run
it!
• Add
domain
• Generate
controller/views
and
run
– SorRng,
paginaRon
are
there
already!
• Add
a
service
and
use
in
controller
• Run
it!

7. Demo…
• SOA
– Render
objects
as
JSON,
XML
etc
– Import
grails.converters.*;
• Parallel
compuRng
in
Services
using
GPars
• Using
other
languages
like
Clojure
in
grails
• …

8. Performance
Concern?
• User
Java
in
high
demanding
place
• Gpars
(Actors,
map
reducer…)
• Use
clojure
in
services
• User
Scala
in
services
• Yes.
It
is
AGILE!

9. Clojure
Demo
• grails
install-­‐plugin
clojure
• New
dir
src/clj
is
created
• Add
file
Addnumber.clj
in
src/clj
(ns
grails)
(def
twenty
20)
(defn
add_numbers
[a
b]
(+
a
b))

10. Call
Clojure
from
Service
class
ClojService
{
boolean
transacRonal
=
false
def
addNumbers(x,
y)
{
clj.add_numbers(x,
y)
}
def
addTwenty(x)
{
clj.add_numbers(x,
clj.twenty)
}
}

11. Call
Service
in
Controller
import
grails.converters.XML;
class
PlayController
{
def
index
=
{
}
def
clojService
def
cljaddnumber={
render
clojService.addNumbers(Integer.parseInt(params.a?:"5"),
Integer.parseInt(params.b?:"4"))
}
def
cljadd20={
render
clojService.addTwenty(Integer.parseInt(params.a?:"10"))
}
}

12. Gpars
Map
Reducer
Demo
//@Grab(group='org.codehaus.gpars',
module='gpars',
version='0.9')
import
staRc
groovyx.gpars.Parallelizer.*
class
ConcurrentService
{
boolean
transacRonal
=
true
def
sqr()
{
def
myNumbers
doParallel{
myNumbers
=
(1..1000).parallel.filter{it
%
2
==
0}.map{Math.sqrt
it}.collecRon
}
myNumbers
}

13. Gpars
Map
Reducer
Demo
def
search(String
key,keys){
key+":"+
keys.replaceAll(key,key.toUpperCase())
/turns
key
to
upper
case
}
def
webs=["a
b
c
d
e
f
g
h
j
k
i
o
as
da
o
sa
ds
h
vcx
aw
s
dsf
gdsg
ds
,
bbx
fdwvcx
786
",
"b
sd
sd
sd
dsfgh
fds
ewr
56y
k
o
aw
n
q
12
g
n
1
uy
t
r",
"sad
assa
sa
sa
sa
sa
456t465367
45
45
23
23
12
453
43
5
3
234
523
",
"8sdf
ds
5ue
we
123
42
hg
h
k
s
x
d
f
t
r
g
h
j
y
k
v
b
n
m
l
qw
ew
c"]
def
reducer(String
key)
{
def
rst
doParallel
{
rst
=
webs.parallel.map
{search(key,it)}.collecRon
}
rst
}}