Scala meetup - Milan, 25 May 2013 Dopo anni di sviluppo Web in Java con le Servlet come base, vediamo come poter sviluppare usando le stesse solide fondamenta con Scala. Scalatra è un toolkit minimale che ci permette di iniziare ad approcciare Scala sul web attraverso le Servlet permettendoci di integrare Scala (o di migrare) in delle WebApp già esistenti. Vedremo in questo quickie come delle funzionalità generiche ed avanzate, implementate con SpringMVC, possono essere implementate con Scalatra.

1. Scala Italy 25 may 2013
Scalatra comparison with SpringMVC
Massimiliano Dessì
1
Monday, May 27, 13

2. GDG Sardegna
Speaker
Max has more than 13 years of experience in programming. He’s a
proud father of three.
Manager of GTUG Sardegna, Founder of SpringFramework IT,
co-founder of Jug Sardegna.
Author of Spring 2.5 AOP.
He works in Energeya as a Product Architect and lives in Cagliari,
Italy.
2
Monday, May 27, 13

3. GDG Sardegna
Scalatra - SpringMVC
CRUD HTML
REST
JSON
Routing
Template
Security
Agenda
3
Monday, May 27, 13

4. GDG Sardegna
Spring , Since 2004 - Java Full Stack - Lot of people involved
now property of VMware
Scalatra , Since 2009 - Scala Http Microframework (DSL)
the BBC, LinkedIn,
the Guardian,
games website IGN,
UK government
rely on Scalatra.
Some info
4
Monday, May 27, 13

5. GDG Sardegna
REST
class JellyBeans extends ScalatraServlet {
get("/jellybs/:id") { ... }
post("/jellybs") { ... }
put("/jellybs/:id") { ... }
delete("/jellybs/:id") { ... }
}
For browser add PUT & DELETE support client side
X-HTTP-METHOD-OVERRIDE or _method=put _method=delete in the post body
class JellyBeansBrowser extends ScalatraFilter with MethodOverride
5
Monday, May 27, 13

6. GDG SardegnaMassimiliano Dessì
Routes
class JellyBeans extends ScalatraServlet {
get("/jellybs/:id") {
val id:Int = params.getOrElse("id", halt(400)).toInt
...
}
get("/jellybs/download/*.*") { //with wildcard
...
}
get("""^/j(.*)/f(.*)""".or) { //REGEX
...
}
post("/jellybs", request.getRemoteHost == "127.0.0.1",
request.getRemoteUser == "admin") {
....
}
6
Monday, May 27, 13

7. GDG Sardegna
REST
@Controller
public class JellyBeansController{
@RequestMapping(value = "/jellybs/{id}", method = RequestMethod.GET)
@ResponseStatus(HttpStatus.OK) //Http 200
public @ResponseBody JellyB getItem(@PathVariable("id") Integer id) {...}
@RequestMapping(value = "/jellybs", method = RequestMethod.POST) //Http 201
@ResponseStatus(HttpStatus.CREATED) //Http 201
public void createJelly(HttpServletRequest req, HttpServletResponse res,
@RequestBody JellyB item) { ... }
@RequestMapping(value = "/jellybs/{id}", method = RequestMethod.PUT)
@ResponseStatus(HttpStatus.NO_CONTENT) //Http 204
public void updateItem(@RequestBody JellyB item, @PathVariable("id") Integer id)
{ ... }
@RequestMapping(value = "/items/{id}", method = RequestMethod.DELETE)
@ResponseStatus(HttpStatus.NO_CONTENT)//204
public void deleteItem(@PathVariable("id") String id) { ... }
}
For browser add PUT & DELETE support client side
X-HTTP-METHOD-OVERRIDE or _method=put _method=delete in the post body
<filter>
<filter-name>hiddenMethodFilter</filter-name>
<filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
</filter>
7
Monday, May 27, 13

8. GDG Sardegna
Routes
class JellyBeans extends ScalatraServlet {
get("/jellybs/:id") {
val id:Int = params.getOrElse("id", halt(400)).toInt
...
}
get("/jellybs/download/*.*") { //with wildcard
...
}
get("""^/j(.*)/f(.*)""".or) { //REGEX
...
}
post("/jellybs", request.getRemoteHost == "127.0.0.1",
request.getRemoteUser == "admin") {
....
}
8
Monday, May 27, 13

9. GDG Sardegna
HandlerMapping
@Controller
public class JellyBeansController{
@RequestMapping(value="/jelly.pdf",method = RequestMethod.GET)
public ModelAndView pdf(HttpServletRequest req,@RequestParam String id)
{
...
}
@RequestMapping(value = "/jellybs/{id}", method = RequestMethod.GET)
public String getItem(@PathVariable("id") Integer id) {
...
}
@RequestMapping(value = "/jellybs", method = RequestMethod.POST)
public void createJelly(@ModelAttribute(”jelly”) JellyB jelly) {
...
}
}
DefaultAnnotationHandlerMapping
SimpleUrlHandlerMapping
ControllerClassNameHandlerMapping
9
Monday, May 27, 13

10. GDG Sardegna
Filter
class JellyBeans extends ScalatraServlet {
before() {
db.acquireConnecion
contentType="text/html"
}
get("/") {
val menu = db.findWelcome()
templateEngine.layout("index.ssp", menu)
}
after() {
db.releaseConnection
}
}
Like Servlet Filter
(or Aspect Oriented Programming)
You can add logic before or the
routes
10
Monday, May 27, 13

11. GDG Sardegna
Handler Interceptor
public interface HandlerInterceptor{
//before call method’s controller
boolean preHandle(HttpServletRequest req, HttpServletResponse res, Object handler)
throws Exception;
//after call method’s controller
void postHandle(HttpServletRequest req, HttpServletResponse res, Object handler,
ModelAndView mav) throws Exception;
//after view render()
void afterCompletition(HttpServletRequest req, HttpServletResponse res, Object
handler, Exception ex) throws Exception;
}
Handler mapped on all controllers (as a property of Handlermapping config)
or mapped on url path with <mvc:interceptors> tags
Like Servlet Filter
(or Aspect Oriented Programming)
You can add logic before or after
the controllers methods
11
Monday, May 27, 13

12. GDG Sardegna
Handlers
Handlers are top level methods for http routines
class JellyBeans extends ScalatraServlet {
notFound {
<h1>Not found</h1>
}
halt(status = 301, headers =
Map("Location" -> "http://www.codemotion.com/"))
get("/jellybs/names/*") {
"Name not found!"
}
}
12
Monday, May 27, 13

13. GDG Sardegna
Handlers
class JellyBeans extends ScalatraServlet {
get("/jellybs/names/:who") {
params("who") match {
case "Cherry" => "Found Cherry!"
case _ => pass() /* call the next matching route route, routes are
matched from bottom up*/
}
}
get("/jellybs/download/:id") {
jellyBeanService.find(params("id")) match {
case Some(jellybean) => Ok(jellybean)
case None => NotFound("Sorry, jellybean not found")
}
}
}
13
Monday, May 27, 13

14. GDG Sardegna
Request Response & Friends
class JellyBeans extends ScalatraServlet {
get("/jellybs/shows/:id") {
//access to request,response, session and params
request.body //request body as a string
request.cookies // cookie map
request.isAjax // is ajaxRequest
request.getSession // HttpServletSession
request.locale // user locale
response.getOutputStream //response outputstream
servletContext.get("myIntParam") //servlet context
val idString = params("id")
val id = params.getAs[Int]("id")
//val id = params.getOrElse("id", halt(500)) //another way
....
}
}
14
Monday, May 27, 13

15. GDG Sardegna
Request Response & Friends
class JellyBeans extends ScalatraServlet {
get("/jellybs/*/conf/*") {
// Matches "GET /jellybs/one/conf/two"
multiParams("splat") // Seq("one", "two")
//wildcard accessible with key splat
}
get("""^/jelly(.*)/fla(.*)""".r) {
// Matches "GET /jellybs/flavor"
multiParams("captures") // == Seq("bs", "vor")
}
}
15
Monday, May 27, 13

16. GDG Sardegna
Gzip
class GzipJellyBeans extends ScalatraServlet with GZipSupport{
get("/") {
<html>
<body>
<h1>This is
<a href="http://en.wikipedia.org/wiki/Sparta">Sparta</a>!
</h1>
</body>
</html>
}
}
16
Monday, May 27, 13

17. GDG Sardegna
Flash message
class FlashServlet extends ScalatraServlet with FlashMapSupport{
post("/jellybs/create") {
flash("notice") = "jellybean created successfully"
redirect("/home") //redirect
}
get("/home") {
ssp("/home") //Scala Server Pages
}
17
Monday, May 27, 13

18. GDG Sardegna
ExceptionResolvers
<bean id="exceptionResolver"
class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
<property name="exceptionMappings">
<props>
<prop key="org.springframework.web.HttpSessionRequiredException">welcome</prop>
...
</props>
</property>
</bean>
or in a annotated @Controller class
@ExceptionHandler
public String requestParamNotPresent(HttpMediaTypeException ex)
18
Monday, May 27, 13

19. GDG Sardegna
Binding
To avoid manual binding from http and our Object Scalatra provide a binding module
case class MyClass(id: Integer, name: String)
post("/myroute") {
val cmd = command[CreateMyClassCommand]
...
}
19
Monday, May 27, 13

20. GDG Sardegna
Binding
Under the hood
abstract class MyClassCommand[S](implicit mf: Manifest[S])
extends ModelCommand[S] with JsonCommand {
implicit def todoStringValidators(b: FieldDescriptor[String]) =
new MyClassStringValidations(b)
}
class CreateMyClassCommand extends MyClassCommand[MyClass] {
protected implicit val jsonFormats = DefaultFormats
val name: Field[String] = asType[String]("name").notBlank.minLength(3)
}
20
Monday, May 27, 13

21. GDG Sardegna
Binding
Under the hood
class MyClassStringValidations(b: FieldDescriptor[String]) {
def startsWithCap(message: String = "%s must start with a capital letter.") =
b.validateWith(_ =>
_ flatMap {
new PredicateValidator[String](
b.name,
"""^[A-Z,0-9]""".r.findFirstIn(_).isDefined,
message).validate(_)
)
}
)
}
21
Monday, May 27, 13

22. GDG Sardegna
CommandObject
@RequestMapping(value = "/items/{id}", method = RequestMethod.PUT)
@ResponseStatus(HttpStatus.NO_CONTENT)
public String updateItem(JellyB item) {
...
}
Spring bind the request body on the object used in the method (JellyB)
Objects Validation with jsr 303 annotation or with Validator Spring Interface
Error message with JSP/JSTL tags
22
Monday, May 27, 13

23. GDG Sardegna
Upload
import org.scalatra.ScalatraServlet
import org.scalatra.servlet.FileUploadSupport
import javax.servlet.annotation.MultipartConfig
@MultipartConfig(maxFileSize=10*1024)
trait StorageRoutes extends FileUploadSupport {
self: ScalatraServlet =>
}
23
Monday, May 27, 13

24. GDG Sardegna
JSON
Automatic Serialization and deserialization of any Case class
object JSONServlet extends ScalatraServlet with JacksonJsonSupport{
case class JellyBean(id: Int, name: String, flavor:String)
protected implicit val jsonFormats: Formats = DefaultFormats
before() {
contentType = formats("json")
}
....
24
Monday, May 27, 13

25. GDG Sardegna
Actors
The routes can returns a Future
class MyActorServlet(system:ActorSystem, myActor:ActorRef)
extends ScalatraServlet with FutureSupport {
import _root_.akka.pattern.ask
implicit val timeout = Timeout(10)
protected implicit def executor: ExecutionContext = system.dispatcher
get("/async") {
myActor ? "Do stuff and give me an answer"
}
get("/fire-forget") {
myActor ! "Hey, you know what?"
Accepted() //if you do not want return a future
}
}
25
Monday, May 27, 13

26. GDG Sardegna
Actors
get("/async") {
myActor ? "Do stuff and give me an answer"
}
get("/fire-forget") {
myActor ! "Hey, you know what?"
Accepted() //if you don’t want return a future
}
class CodemotionActor extends Actor {
def receive = {
case "Do stuff and give me an answer" => sender ! "The answer is 42"
case "Hey, you know what?" => println("Yeah I know...")
}
}
}
26
Monday, May 27, 13

27. GDG Sardegna
Akka
Akka start in the Bootstrap of Scalatra
class ScalatraBootstrap extends LifeCycle {
val system = ActorSystem()
val codemotionActor = system.actorOf(Props[CodemotionActor])
override def init(context: ServletContext) {
context.mount(new JSONServlet, "/jellybs/*")
context.mount(new FrontServlet, "/template/*")
context.mount(new MyActorServlet(system, codemotionActor), "/actors/*")
}
override def destroy(context:ServletContext) {
system.shutdown()
}
}
27
Monday, May 27, 13

28. GDG Sardegna
Deployment
Scalatra is based on regular Java Servlet 3.0
it can start from:
Standalone from jetty embedded
From Servlet container
Heroku
Jelastic
CloudBees
GAE (not out of the box )
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
version="3.0">
<listener>
<listener-class>org.scalatra.servlet.ScalatraListener</listener-class>
</listener>
<servlet-mapping>
<servlet-name>default</servlet-name>
<url-pattern>/img/*</url-pattern>
<url-pattern>/css/*</url-pattern>
<url-pattern>/js/*</url-pattern>
<url-pattern>/assets/*</url-pattern>
</servlet-mapping>
</web-app>
28
Monday, May 27, 13

29. GDG Sardegna
JSON
Automatic Serialization and deserialization of any Case class
object JSONServlet extends ScalatraServlet with JacksonJsonSupport{
...
get("/jellybs/all"){
jellyBeanRepo.all //from class to json
}
post("/jellybs/create") {
val jb = parsedBody.extract[JellyBean] //from json to class
...
}
}
29
Monday, May 27, 13

30. GDG Sardegna
JSON
30
JSON with third party lib es Jackson
@JsonCreator
public JellyB(Map map) {...}
@JsonAnyGetter
public Map toMap() {...}
Automatic binding
public @ResponseBody JellyB getItem(...)
public void updateItem(@RequestBody JellyB item)
Monday, May 27, 13

31. GDG Sardegna
Template
Html inline,
Scalate
Twirl (Play2 template)
Scalate
mean
SSP (Scala Server Page)
Scaml
Mustache
Jade
31
Monday, May 27, 13

32. GDG Sardegna
Template
class ScalateServlet extends ScalatraServlet with ScalateSupport{
get("/"jellybeans/ssp) {
contentType="text/html"
ssp("/index", "foo" -> "uno", "bar" -> "two")
// the layout used it’s WEB-INF/layouts/default.ssp
}
get("/jellybeans/jade") {
jade("/index", "layout" -> "", "foo" -> "one", "bar" -> "two")
// render without a layout.
}
get("/jellybeans/direct") {
templateEngine.layout("/jellybeans/index.ssp")
//direct invoking of scalate
}
32
Monday, May 27, 13

33. GDG Sardegna
Template
SSP
<%@ var body: String %>
<%@ var title: String = "Some Default Title" %>
<%@ var head: String = "" %>
<html>
<head>
<title>${title}</title>
<%-- page specific head goes here --%>
${unescape(head)}
</head>
<body>
<p>layout header goes here...</p>
${unescape(body)}
<p>layout footer goes here...</p>
</body>
</html>
33
Monday, May 27, 13

34. GDG Sardegna
Template
JADE
!!! 5
html(lang="en")
head
title= pageTitle
:javascript
if (foo) {
bar()
}
body
h1 Jade - node template engine
#container
- if (youAreUsingJade)
p You are amazing
- else
p Get on it!
:coffeescript
alert "Hello, Coffee!"
34
Monday, May 27, 13

35. GDG Sardegna
Template
Mustache
Hello {{name}}
You have just won ${{value}}!
{{#in_ca}}
Well, ${{taxed_value}}, after taxes.
{{/in_ca}}
35
Monday, May 27, 13

36. GDG Sardegna
Template
SCAML
!!! XML
!!!
%html
%head
%title Myspace
%body
%h1 I am the international space station
%p Sign my guestbook
36
Monday, May 27, 13

37. GDG Sardegna
ViewResolver
JSP, JSTL, Tiles, FreeMarker, XSLT, PDF, Velocity, JExcelApi,
JSON, Atom, RSS, JasperReports
Explicit view with different ViewResolver with different order
values, or with ContentTypeNegotiationViewResolver
mapping different mediaTypes
37
Monday, May 27, 13

38. GDG Sardegna
Authentication & Security
Scalatra uses Scentry a porting of Ruby Warden authentication
class OurAuthStrategy(protected override val app: ScalatraBase, realm: String)
extends BasicAuthStrategy[User](app, realm) {
protected def validate(userName: String, password: String): Option[User] = {
if(userName == "myusername" && password == "secret") Some(User("myusername"))
else None
}
protected def getUserId(user: User): String = user.id
}
case class User(id: String)
38
Monday, May 27, 13

39. GDG Sardegna
Authentication & Security
Now we need to combine our strategy and ScentrySupport
trait AuthenticationSupport extends ScentrySupport[User] with BasicAuthSupport[User] {
self: ScalatraBase =>
val realm = "Scalatra Basic Auth Example"
protected def fromSession = { case id: String => User(id) }
protected def toSession = { case usr: User => usr.id }
protected val scentryConfig = (new ScentryConfig {}).asInstanceOf[ScentryConfiguration]
}
39
Monday, May 27, 13

40. GDG Sardegna
Authentication & Security
Now we need to combine our strategy and ScentrySupport
trait AuthenticationSupport extends ScentrySupport[User] with BasicAuthSupport[User] {
....
override protected def configureScentry = {
scentry.unauthenticated {
scentry.strategies("Basic").unauthenticated()
scentry.strategies("")
}
}
override protected def registerAuthStrategies = {
scentry.register("Basic", app => new OurBasicAuthStrategy(app, realm))
}
protected def validate(userName: String, password: String): Option[User] = {
if(userName == "scalatra" && password == "scalatra") Some(User("scalatra"))
else None
}
}
40
Monday, May 27, 13

41. GDG Sardegna
Authentication & Security
Now we can use the Authentication for all routes defined in our Authenticated Servlets
class AuthenticatedServlet extends ScalatraServlet with AuthenticationSupport{
//every route goes under authentication
}
Unauthenticated user will see a browser prompt login
41
Monday, May 27, 13

42. GDG Sardegna
SpringSecurity
FilterServlet to protect urls, roles and AOP intercepting based on User Roles
<filter>
<filter-name>springSecurityFilterChain</filter-name>
<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
</filter>
<filter-mapping>
<filter-name>springSecurityFilterChain</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<sec:http>
" " <sec:form-login login-page="/login.jsp"
login-processing-url="/j_security_check"
default-target-url="/"
" " " always-use-default-target="true"
authentication-failure-url="/loginError.jsp"/>
" " <sec:logout logout-url="/logout.jsp" invalidate-session="true"
logout-success-url="/login.jsp" />
" " <sec:intercept-url pattern="/styles/**" filters="none"/>
" " <sec:intercept-url pattern="/scripts/**" filters="none"/>
" " <sec:intercept-url pattern="/img/**" filters="none"/>
" " <sec:anonymous username="guest" granted-authority="ROLE_GUEST" />
"
42
Monday, May 27, 13

43. GDG Sardegna
Test
Test with Specs2
class FrontServletSpec extends ScalatraSpec {
def is =
"GET / on FrontServlet" ^
"should return status 200" ! root200 ^
end
addServlet(classOf[FrontServlet], "/*")
def root200 = get("/") {
status must_== 200
}
}
43
Monday, May 27, 13

44. GDG Sardegna
Q & A
GTUG Sardegna
44
Monday, May 27, 13

45. GDG Sardegna
Thanks for your attention!
Massimiliano: @desmax74
GTUG Sardegna
45
Thanks for you attention!
Massimiliano: @desmax74
Monday, May 27, 13