Managing Binary Compatibility in Scala (Scala Lift Off 2011)
Reactive Web Applications with Scala & Liftweb - CodeWeek 2015
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Reactive Web Applications using Scala & Liftweb Andrea Zanda CTO & Co-founder [email protected] Riccardo Sirigu Full Stack Dev [email protected]
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Transcript of Reactive Web Applications with Scala & Liftweb - CodeWeek 2015
Reactive Web Applications using Scala & Liftweb
Andrea ZandaCTO & [email protected]
Riccardo SiriguFull Stack [email protected]
DONA ANCHE TU su Rete del Dono#sardiniacodeweek
http://www.retedeldono.it/it/progetti/sardegna-2050/sardinia-code-week-2015
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Which is the tech challenge?
Reactive Manifesto
● The techniques and technologies traditionally used in a class of Reactive and Interactive Systems is gaining quite a bit of attention from the mainstream developers community
● Recently, the Reactive Manifesto was defined to summarise the key traits of “Reactive Applications”
Reactive Manifesto
● Responsive: Timely react to stimuli
● Event-Driven: modular, asynchronous
● Resilent: Tolerate failures functionally and ideally temporally
● Scalable: Gracefully scale up and down depending on load demands
https://github.com/zaza81/lift-codeweek
@MarioBot /codeweek banana luca
gmr-codeweek.cloudapp.net
Scala● Functional (style) programming● Everything is an Object● Run on JVM● Practical expressivity
○ Expressive Power
○ List(1,2,3,4).map(x => x + 1)○ What vs How
● N(Bugs) ∝ N(LOC)○ Fewer LOC fewer bugs○ Halstead complexity measures
Scala vs Java● Every operator is a method call○ 12 + 4 (12).+(4)○ “#name” #> “david”○ “codeWeek” indexOf “w”
● Object Equality○ List(56,13,75) == List(56,13,75)
● Optional Types○ NullPointerException○ val secret: Option[String] = Some(“zbmdfbmknnaprzvds=”)○ val secret: Option[String] = None
Scala vs Java● Immutable data structuresscala> val even = List(2,4)scala> 6 :: 8 :: evenres0: List[Int] = List(6,8,2,4)
● Type inferencescala> Map('a' -> 1, 'b' -> 2)res2: scala.collection.immutable.Map[Char,Int] = Map(a -> 1, b -> 2)
Scala vs Java
class User(val email: String)
class User{ private String email;
public User(String email){this.email = email
}public String getEmail(){return email;
}}
Scala (1st class) Functions
var botMe = (name: String) => “@” + name + ”Bot”botMe: String => String = <function1>
val names = “Riccardo” :: “Andrea” :: “Mario” :: Nilnames: List[String] = List(Riccardo, Andrea, Mario)
names.map(botMe)res0: List[String] = List(@RiccardoBot, @AndreaBot, @MarioBot)
Objects EverywhereFunctions are Objects
(x: Int) => x * x * x
..is expanded to..
new Function1[Int, Int] { def apply(x: Int) = x * x * x
}
Objects Everywhereval f = (x: Int) => x * x * xf(2)
val f = new Function1[Int, Int] { def apply(x: Int) = x * x * x}
f.apply(2)
Companion Objects
Companion Objects• Same name & same source file as the class
class User extends MegaProtoUser[User] { def getSingleton = User // reference to the companion object below def allAccounts : List[Account] = Account.findAll(By(Account.owner, this.id))}// Create a "companion object" to the User class (above).// The companion object is a "singleton" object that shares the same// name as its companion class.object User extends User with MetaMegaProtoUser[User] { override def dbTableName = "users" }
Pattern Matching
• Switch case on steroids
User.findById(“000001”) match {case Some(user) => println(user.name)case Empty => println(“No User Found!”)
}
Scala Actors
Scala Actors● Manual threading and locking is difficult Actor abstraction● Concurrent processes that communicate by exchanging messages● Actor encapsulates both state and behavior● Fire&Forget
chatserver ! msgActor Model
LIFT me up
Introducing LiftWhy?
● Based on Scala● Comet and Ajax, js abstractions● Designer friendly templates View First● Security
○ injections, XSS, CSRF...○ OWASP Top 10
http://seventhings.liftweb.net/http://lift.la/blog/lift-state-and-scaling
Setting the environment
+
MVVM in concrete
View Model
HTML page Scala Class (ORM)
Snippet
(MV)
CSS Selectors
“#id_element” #> <p> Element Content</p>
SHtml
“#id_text” #> SHtml.text(“text”, textVar = _) & “#id_submit” #> SHtml.submit(“Submit”, processResult())
def processResult(): JsCmd = { //do something
S.notice(“Work Done”)}
Comet Actors
Comet
• Server Push• Real time event-based systems• Thread per request, long polling
Comet
One thread per request leads to…….. SCALABILITY ISSUES
Web container request suspension or continuation
Demo Time
DONA ANCHE TU su Rete del Dono#sardiniacodeweek
http://www.retedeldono.it/it/progetti/sardegna-2050/sardinia-code-week-2015
