Scalatra Spring MVC From Java to Scala Web Akka Actors

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.
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3. GDG Sardegna
Scalatra - SpringMVC
CRUD HTML
REST
JSON
Routing
Template
Security
Agenda
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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
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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
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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") {
....
}
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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>
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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") {
....
}
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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
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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
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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
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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!"
}
}
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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")
}
}
}
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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
....
}
}
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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")
}
}
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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>
}
}
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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
}
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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)
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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]
...
}
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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)
}
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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(_)
)
}
)
}
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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
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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 =>
}
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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")
}
....
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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
}
}
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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...")
}
}
}
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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()
}
}
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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>
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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
...
}
}
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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
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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
}
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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>
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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!"
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35. GDG Sardegna
Template
Mustache
Hello {{name}}
You have just won ${{value}}!
{{#in_ca}}
Well, ${{taxed_value}}, after taxes.
{{/in_ca}}
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36. GDG Sardegna
Template
SCAML
!!! XML
!!!
%html
%head
%title Myspace
%body
%h1 I am the international space station
%p Sign my guestbook
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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
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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)
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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]
}
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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
}
}
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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
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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" />
"
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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
}
}
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44. GDG Sardegna
Q & A
GTUG Sardegna
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45. GDG Sardegna
Thanks for your attention!
Massimiliano: @desmax74
GTUG Sardegna
45
Thanks for you attention!
Massimiliano: @desmax74
Monday, May 27, 13