Whistle-­‐stop
tour
of
the
Li#
web
framework
and
demonstra:ng
why
the
real-­‐:me
web
should
ma=er
to
you
www.devoxx.com

Agenda
! Overview
of
Scala
! Li#’s
Ra:onale
! The
real-­‐:me
web
! Li#’s
awesome
feature
set
! Why
Scala
makes
Li#
possible
www.devoxx.com

About
Me
! Project
commi=er
on
Li#
! Manufacturing
and
marke:ng
automa:on
is
my
day-­‐job
(industrial
systems)
! Whole
raH
of
experience
with
both
dynamic
and
sta:c
languages
! Desktop
and
Web
applica:on
development
www.devoxx.com
! Coding
Scala
and
LiH
since
end
of
2007

What
is
Scala?
(10,000
foot
view!)
! Scala
is
func:onal
! Scala
is
object
orientated
! Scala
is
mul:-­‐paradigm!
OO
and
FP
hybrid...
! Designed
by
Mar:n
Odersky
(Java
generics)
! Runs
as
fast
as
na:ve
Java
code
! Fully
interoperable
with
exis:ng
Java
libraries
www.devoxx.com
! More
type-­‐safe
than
Java

Scala
in
the
wild?
www.devoxx.com

Scala
in
breif….
! What
follows
is
an
overview
of
core
Scala
language
features
www.devoxx.com

Immutability
val example = “Devoxx”
! Immutable
values
are
assigned
with
the
“val”
keyword
! Immutability
is
your
long-­‐lost
friend:
!
No
need
to
synchronise
!
Never
need
to
copy
vars
“just
in
case”
!
Great
for
hash
keys
www.devoxx.com
! Be=er
for
garbage
collector

Case
Classes
case class Foo(bar: String, baz: List[Int])
! Func:onality
you
get
for
free:
!
“new”
keyword
is
redundant
!
bar
and
baz
proper:es
(immutable
by
default)
!
toString,
hashCode,
and
equals
et
al
!
Pa=ern
matching
with
parameter
extrac:on
www.devoxx.com

Singletons
object ChatServer extends Actor
! ChatServer
is
a
singleton
! One
instance
per
classloader
! Can
be
passed
as
parameter…
it’s
an
instance
www.devoxx.com

Composi:on
with
Traits
! Finely-­‐grained
aggrega:on
of
func:onality
! Mul:ple-­‐inheritance
without
diamond
problem[1]
! Extensively
used
in
Li#
object sally extends Person(“Sally”)
with Female
with Runner
def womansRun(who: Female with Runner)
www.devoxx.com
//=> womansRun(sally)
[1]
h=p://en.wikipedia.org/wiki/Diamond_problem

Func:on
Passing
! Encapsulates
logic
concisely
! Wildcard
shorthand
keeps
things
simple
! Func:ons
are
instances
that
can
be
passed
// make x a function that lower cases input
val x: (String) => String = (str) => str.toLowerCase
www.devoxx.com
// alter the request encoding
LiftRules.early { _.setCharacterEncoding(“UTF-8”) }

Pa=ern
Matching
! Match
against
case
classes
!
Parameter
extrac:on
!
Great
for
message
/
event
handling
!
Test
against
parameters:
case Person(name, 35) =>
! Declara:ve
expression
of
logic
case Messages(m) => msgs = m
www.devoxx.com
case s: String if s.length > 0 => msgs ::= s

XML
Literals
! XML
is
first-­‐class
! Ripe
for
templa:ng
abuse!
! Very
handy
for
development
but
Li#
provides
strong
abstrac:ons
for
templates
val links = (“Link A”, http://…) ::
(“Link B”, “http://…”) :: (“Link C”, https://…) :: Nil
www.devoxx.com
val myLinkList =
<ul>{ links.flatMap({case (name,url) =>
<li><a href={url}>{name}</a></li>}) }
</ul>

Actors
! Being
“real-­‐:me”
means
events
! Lightweight
concurrency
model
! With
very
nice
syntax
! Implemented
as
a
library!
object DevoxxActor extends Actor { …… }
case class Talk(name: String)
www.devoxx.com
// asyncronusly send the talk message to the actor
DevoxxActor ! Talk(“Lift web framework”)

What
is
LiH?
! Web
framework
wri=en
in
Scala
! 3
years
old,
founded
by
David
Pollak
! Leverages
the
best
of
Scala
language
features
! Takes
the
best
ideas
from
other
frameworks
! Makes
real-­‐:me
web
applica:ons
accessible
! Massively
scalable
www.devoxx.com

Why
another
framework?
! Developers
needn't
be
plumbers
! Unifies
the
best
of
other
framework
concepts
!
Granular
sessions
and
security
a
la
Seaside
!
Flash-­‐to-­‐bang
produc:vity
a
la
Rails
!
Designer
friendly
templates
a
la
Wicket
! Advanced
features
like
comet
work
OOTB
www.devoxx.com
! Tough
to
be
truly
real-­‐:me
with
exis:ng
tech

Web
Beginnings
! Very
person
-­‐>
machine
affair
! Primary
uses:
!
Shopping
!
Banking
!
CRUD
opera:ons
! 56k
modems
(yikes!)
www.devoxx.com

Web
2.0
! Behaviour
shiH
-­‐>
more
social
! Different
usage
models:
!
Person
-­‐>
Machine
-­‐>
Machine
(mashups)
!
Person
-­‐>
Person
(Facebook,
Twi=er)
!
Machine
-­‐>
Machine
-­‐>
Person
(micro-­‐formats)
! Internet
becomes
society
cornerstone
www.devoxx.com

Real
Time
Web
! Users
demand
instant
gra:fica:on
! Peer-­‐to-­‐peer
news
/
informa:on
streams
! Business
informa:on
in
constant
flux
! Online
interac:ve
games
! Real
Time
Web
is
the
next
evolu2onary
step...
www.devoxx.com

View
First
! Its
not
MVC
! Your
typical
page
has
more
than
a
single
piece
of
dynamic
content
! Code
in
the
view
usually
means
some
“seep”
of
business
logic:
thus,
NO
code
in
the
view
! Only
well-­‐formed
XHTML;
no
string
replacement
–
e.g.
{{myvar}}
www.devoxx.com
! Designer
friendly
dynamic
content
markup

Snippets
! A
“snippet”
in
Li#
represents
a
collec:on
of
applica:on
logic
! One
snippet
can
be
called
on
n
number
of
pages,
n
number
of
:mes
! A
snippet
is
a
normal
Scala
class
or
object:
there
is
no
black
magic
www.devoxx.com
! Lookup
via
reflec:on
or
manual
wiring

What
a
bind…
class Example {
def nameForm(xhtml: NodeSeq) = {
var name = “”
def doSubmit { println(“Submitted…”); }
bind("f", xhtml,
"name" -> SHtml.text(name, name = _),
"submit" -> SHtml.submit(doSubmit _)
)
}
}
<lift:example.name_form>
<p><f:name /></p>
www.devoxx.com
<p><f:submit /></p>
</lift:example.name_form>

Security
! Page
elements
have
session
specific
opaque
GUIDs
to
reference
server
components
(impossible
to
do
CSRF[1])
<input name=“F677071620957IFD” type=“text” />
! Callback
func:ons
also
use
similar
GUIDs
so
that
sensi:ve
IDs
etc
are
not
exposed
www.devoxx.com
/somepath?F677071620979LIK=_
[1]
h=p://en.wikipedia.org/wiki/Cross-­‐site_request_forgery

Site
Map
!
Declara:ve
and
granular
defini:on
of
page
and
UI
access
rules
! Enforced
long
before
the
page
content
is
processed
or
rendered
–
its
very
fast.
! Can
generate
site
menus
even
with
complex
rules
on
what
different
users
see
www.devoxx.com
! Unified
access
control
model

Persistence
! Li#
includes
“Mapper”
which
is
a
lightweight
ORM
of
similar
design
to
Ac:veRecord
in
Rails
! Use
any
backend
persistence
system
you
want
(Hibernate,
JPA
etc)
! Write
custom
back-­‐ends
using
Li#
Record
–
provides
OOTB
valida:on
and
CRUD
seman:cs;
you
provide
the
implementa:on
www.devoxx.com

REST
and
WebServices
! REST
via
state(full/less)
dispatching
! Declara:ve
rules
for
URI
-­‐>
handler
dispatch
! LiH
has
awesome
support
for
JSON:
!
Slick
DSL
for
construc:on
/
parsing
!
~300
:mes
faster
than
Scala
JSON
parser
!
Faster
deseriliza:on
than
Java
www.devoxx.com
! Na:ve,
first-­‐class
XML
support
in
Scala

Technology
Support
! AMQP
! Tex:le
! XMPP
! OpenID
! JTA
! PayPal
www.devoxx.com
! …and
lots
more!

Summary
! Scala’s
object
model
is
a
superset
of
Java’s
! Scala
traits:
powerful
and
granular
composi:on
! Scala
is
syntac:cally
simpler
than
Java
or
Ruby
! Scala’s
design
led
to
Li#’s
design
! Li#
makes
the
real-­‐:me
web
simple
! Li#
is
the
culmina:on
of
many
great
ideas
www.devoxx.com