Play framework 2 : Peter Hilton

Play framework 2
@PeterHilton at #JAXLondon on 17 October 2012

2
Peter Hilton

■ (sorry, I am not Guillaume Bort)
■ Web developer and Operations Director at
Lunatech Research in Rotterdam
■ Web application architecture, design and construction
■ Technical project management and functional design
■ Play framework committer since 2010
■ Co-author of the book Play for Scala (Manning)

3
About Lunatech

■ Founded in Ro*erdam in 1993 as an IT consul6ng, product
research and development team
■ We build web applica6ons, web services, large-‐scale document-‐
processing and message-‐processing applica6ons, online products
■ Leverage cuBng-‐edge open-‐source soCware plaDorms
■ Invest in product research and development
■ Play framework; Java EE -‐ JBoss AS, Seam, JPA, jBPM, Drools;
back-‐end -‐ PostgreSQL, Linux; front-‐end -‐ jQuery, Backbone, _.js
■ Agile soCware development -‐ self-‐managing technical teams

4

“ Play introduces high-‐produc6vity
type safe web development
Presenta6on goal: show you how cool Play is

5
Outline

■ What Play is and why it matters
(web architecture)
■ High-productivity web development
(but for Java and Scala developers)
■ Developer Experience (DX) that doesn’t suck
■ Type safe compile-time checked web development
■ HTML5 front-end development

6
What Play is

■ Full-stack web framework (what you need to build an app)
■ Simple, ﬂexible and powerful HTTP interface
■ High-productivity web development
■ High-performance scalable architecture
■ Designed by web developers for web developers
■ Play is fun

h&p://www.ﬂickr.com/photos/roninsfx/5568957616/

h&p://www.ﬂickr.com/photos/deerwooduk/579761138/

9

“ What is the focal-‐point of web
applica6on architecture?

10

“ It’s the web browser, stupid

11
Why Play maCers

The Back bu*on works

Play’s stateless architecture is based on HTTP.

When a web framework starts an architecture ﬁght
with the web, the framework loses.

12
Why Play maCers

Back The Reload bu*on works
bu*on
During development, just reload the page
to see changes in your Java (or Scala) code.
That’s high-‐produc6vity web development.

13
Why Play maCers

Back You design the URL Reload
bu*on bu*on
You can use ‘clean’ URLs:
/products
/product/42
/product/42/comments

14
Why Play maCers

Back Usability (DX) URL Reload
bu*on bu*on
Convenient HTTP API
and template syntax
Clear error messages
and short stack traces

15

“ What’s the story behind the heart icon?

“ There isn’t one.
Feel free to make one up :)
Guillaume Bort

16

“ Play doesn’t ﬁght web architecture
Stateless, HTTP-‐centric architecture…

Play framework 2 : Peter Hilton

18
Stateless architecture

■ No state in the application’s web tier
■ e.g. Java Servlet API’s HTTP session
(which isn’t actually part of HTTP)
■ State belongs in other tiers
■ HTTP client, server cache or database
■ Web application behaviour deﬁned by URLs (requests)
■ Exception for identifying authenticated user by cookie

19
Stateless architecture -‐ why

■ Simpliﬁes application development and testing
■ (a URL is all you need for reproducability)
■ Matches the web’s stateless HTTP architecture
■ Avoids synchronising state between additional layers
■ (‘synchronisation’ should ring tech design alarm bells)
■ Enables cloud deployment and horizontal scalability
■ (search the web for “Play framework Heroku”)

21

“ Dear Java devs, PHP and Rails devs
have been laughing at you for years
… every 6me they reload a page’s code changes

22
Code reloading

■ During development, reload the page to see changes in:
■ Java and Scala classes
■ conﬁguration ﬁles
■ templates.
■ Play pre-compiles classes and templates for better
performance in production mode
■ This just works out-of-the-box

23

“ URLs want to be loved too
REST architecture isn’t just for web service APIs

24

h t t p : / a p p . e a m p l e . c o m / W r o o t D r
/ x a R i e
c t o r 1 / e l e s A l a e s s s o n I d = x 8
y S rv t On P n ? e i
1 n j 3 8 a v g L O L d x p a e w q & a c t i o n = N e x t
n j n
P a g & H n e B a d e r r s = a l s e e n t t y
e o y g Ca e f & i
I d 1 2 9 9 1 2 7 4 3 & p r o c e s s N m e = n l a d e n
= a U
S w a l l o w C o m p u t a t i o n & r o l e = p e o n & d a t
e = 1 4 % 2 F 2 % 2 F 2 0 1 2 & f l g e t i n g = 0 1 0
0 a S t s
1 0 1 1 & r e t u r n = % 2 F v i d e o s % 2 F r i c k r o l l . a v i

h&p://www.ﬂickr.com/photos/shyroii/4817446191/

26
URL design (HTTP rouMng)

■ Clean URLs are stable URLs:
■ http://example.com/products
■ http://example.com/product/42
■ Read it, bookmark it, mail it, tweet it
■ URL-centric design:
■ Design the URL scheme before you start coding
■ Conﬁgure your application’s URLs in one ﬁle

27
URL design (HTTP rouMng)

■ Designed URLs are clean URLs:
■ http://example.com/products
■ http://example.com/product/42
■ Corresponding Play routing conﬁguration:

#
HTTP
routes
configuration
file

#
method,
URL
path,
controller
action
method
(and
params)

GET

/products

controllers.Products.list()

GET

/product/:id

controllers.Products.details(id:Long)

28
# HTTP routes conﬁguraMon ﬁle

GET

/

controllers.Application.index()

GET

/products

controllers.Products.list()

POST

/products

controllers.Products.add(p:
Product)

GET

/product/:id

controllers.Products.details(id:
Long)

DELETE
/product/:id

controllers.Products.delete(id:
Long)

GET
/products.json

controllers.Products.listJSON()

GET
/product/:id.json
controllers.Products.detailsJSON(id:Long)

29

“ You have to be a genius to successfully
use some web frameworks
For the rest of us, there are good error messages

31
Where’s the actual error message?

13:07:55,796
ERROR
[[PersonServlet]]
Servlet.service()
for
servlet

PersonServlet
threw
exception
javax.ejb.EJBException:
null;
CausedByException
is:

null

at
org.jboss.ejb3.tx.Ejb3TxPolicy.handleExceptionInOurTx(Ejb3TxPolicy.java:46)

at
org.jboss.aspects.tx.TxPolicy.invokeInOurTx(TxPolicy.java:70)

at
org.jboss.aspects.tx.TxInterceptor$Required.invoke(TxInterceptor.java:134)

at
org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:98)

at
org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInterceptor.java:61)

at

at
org.jboss.ejb3.stateless.StatelessInstanceInterceptor.invoke(StatelessInstanceInterceptor.java:39)

at

at
org.jboss.aspects.security.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java:63)

at

at
org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterceptor.java:32)

at

at
org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(AsynchronousInterceptor.java:91)

at

at
org.jboss.ejb3.stateless.StatelessContainer.dynamicInvoke(StatelessContainer.java:189)

at
org.jboss.aop.Dispatcher.invoke(Dispatcher.java:107)

at
org.jboss.ejb3.remoting.IsLocalInterceptor.invoke(IsLocalInterceptor.java:37)

at

at
org.jboss.ejb3.stateless.StatelessRemoteProxy.invoke(StatelessRemoteProxy.java:88)

at
$Proxy76.getAllPeople(Unknown
Source)

at
uk.co.mediaport.web.PersonServlet.showTelephones(PersonServlet.java:54)

at
uk.co.mediaport.web.PersonServlet.doPost(PersonServlet.java:45)

at
uk.co.mediaport.web.PersonServlet.doGet(PersonServlet.java:34)

at
javax.servlet.http.HttpServlet.service(HttpServlet.java:697)

at

at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)

at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)

at
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:81)

at

at

at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)

at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)

at
org.jboss.web.tomcat.security.CustomPrincipalValve.invoke(CustomPrincipalValve.java:39)

at
org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:159)

at
org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:59)

at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)

at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)

at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)

at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)

at
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856)

at
org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:744)

at
org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)

at
org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
32

at
java.lang.Thread.run(Thread.java:595)

java.lang.NullPointerException

at
uk.co.mediaport.core.PeopleBean.getAllPeople(PeopleBean.java:33)

at
sun.reflect.NativeMethodAccessorImpl.invoke0(Native
Method)

at
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)

at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at
java.lang.reflect.Method.invoke(Method.java:585)

at

at
org.jboss.ejb3.AllowedOperationsInterceptor.invoke(AllowedOperationsInterceptor.java:32)

at

at
org.jboss.aspects.tx.TxPolicy.invokeInOurTx(TxPolicy.java:66)

at
org.jboss.aspects.tx.TxInterceptor$Required.invoke(TxInterceptor.java:134)

at

at
org.jboss.aspects.tx.TxPropagationInterceptor.invoke(TxPropagationInterceptor.java:61)

at

at
org.jboss.ejb3.stateless.StatelessInstanceInterceptor.invoke(StatelessInstanceInterceptor.java:39)

at

at
org.jboss.aspects.security.AuthenticationInterceptor.invoke(AuthenticationInterceptor.java:63)

at

at
org.jboss.ejb3.ENCPropagationInterceptor.invoke(ENCPropagationInterceptor.java:32)

at

at
org.jboss.ejb3.asynchronous.AsynchronousInterceptor.invoke(AsynchronousInterceptor.java:91)

at

at
org.jboss.ejb3.stateless.StatelessContainer.dynamicInvoke(StatelessContainer.java:189)

at
org.jboss.aop.Dispatcher.invoke(Dispatcher.java:107)

at
org.jboss.ejb3.remoting.IsLocalInterceptor.invoke(IsLocalInterceptor.java:37)

at

at
org.jboss.ejb3.stateless.StatelessRemoteProxy.invoke(StatelessRemoteProxy.java:88)

at
$Proxy76.getAllPeople(Unknown
Source)

at
uk.co.mediaport.web.PersonServlet.showTelephones(PersonServlet.java:54)

at
uk.co.mediaport.web.PersonServlet.doPost(PersonServlet.java:45)

at
uk.co.mediaport.web.PersonServlet.doGet(PersonServlet.java:34)

at

at

at

at

at
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:81)

at

at

at
org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)

at
org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)

at
org.jboss.web.tomcat.security.CustomPrincipalValve.invoke(CustomPrincipalValve.java:39)

at
org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:159)

at
org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:59)

at
org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)

at
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)

at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)

at
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)

http://localhost/ 33

Parse error: syntax error, unexpected T_VARIABLE
in /usr/local/www/htdocs/index.php on line 3

35

“ Play 2 con6nues the innova6on
First-‐class support for both Java and Scala
Type-‐safe templates
Compile-‐6me checking
Asynchronous HTTP programming

h&p://www.ﬂickr.com/photos/anoldent/3642351368

37
Play in Java and Scala

■ Play 2.0 provides parallel APIs for Java and Scala,
for example, a controller action:

//
Java
controller
action
method
public
static
Result
index(String
name)
{

return
ok("Hello"
+
name);
}

//
Scala
controller
action
method
def
hello(name:
String)
=
Action
{

Ok("Hello
"
+
name)
}

38
Play 2.0 Scala implementaMon

■ Play 2.0 is itself implemented in Scala
■ Scala removes the need for so much bytecode
enhancement in the Java API (which is how Play 1.x works)
■ There is less ‘magic’ and strangeness in the API
■ The code you see in the IDE is the code that runs
■ Scala source code not necessarily harder to read

39

“ Templates want to be beau6ful too
Type safe template parameter delcara6ons
Minimal interference with HTML mark-‐up

40
Type-‐safe template parameters

■ Templates include type-safe parameter declarations
■ Similar to the lightweight template syntax in Play 1.x
■ Templates are compiled into class ﬁles for run-time speed

@(products:
List[Product])
<ul>

@for(product
<-‐
products)
{

<li
class="@product.type">@product.name</li>
}

</ul>

41
Template funcMons

■ Play 2.0’s template system is based on Scala
■ A template is a Scala function that you call from your code

//
Render
the
‘Products.list’
template
in
Java
code.
Html
html
=
views.html.Products.list.render(products);

//
e.g.
as
the
result
of
a
controller
action
method.
public
static
Result
list()
{

final
List<Product>
products
=
Products.list();

return
ok(views.html.Products.list.render(products));
}

Template syntax starts with @ 42

Template parameter declaration

@(products:
List[Product])

@if(products.isEmpty)
{

<h1>No
products</h1>

} No delimiter for the end of
a template syntax section

43

@(products:
List[Product])

@if(products.isEmpty)
{

<h1>No
products</h1>

}
else
{

<h1>@items.size
products</h1>

}
Output the value of an expression

44

Deﬁne a ‘tag’ - output a details page link

@display(product:
models.Product)
=
{

<a
href="@routes.Products.details(product.id)">

@product.name

</a>
}

<ul>
@for(product
<-‐
products)
{

@display(product)
}

</ul>
Use the ‘display’ tag

45

<section
class="content">

…

</section>

@footer()

Include the ‘footer’ template
(i.e. call the ‘footer’ function)

main.scala.html 46

@(title:
String)(content:
Html)
<!DOCTYPE
html>
<html>
Two parameter lists

<head>
(one parameter each)

<title>@title</title>

</head>

<body>

@content

</body> Deﬁne a page layout
</html> template called ‘main’

index.scala.html
@main("Home
page")
{ Render the ‘main’ template,

<h1>Welcome</h1> passing two parameters
}

47

“ Dear PHP and Rails developers,
run6me errors make you look bad
Using unit tests to ﬁnd syntax errors is a hack
There is a solu6on…

49
Compile-‐Mme checking

■ Not just Java and Scala classes
■ HTTP routes file (maps URLs to controller actions)
■ Templates
■ JavaScript files (using Google Closure Compiler)
■ CoffeeScript files (alternative to JavaScript)
■ LESS style sheets (alternative to CSS)
■ Fewer errors at run-time

controllers/Products.java 50

public
class
Products
extends
Controller
{

public
static
Result
details(final
Long
id)
{

return
ok();

}
}

conf/routes
GET
/product/:id

String)

controllers/Products.java 50

public
class
Products
extends
Controller
{

public
static
Result
details(final
Long
id)
{

return
ok();

}
}

Incompatible types

conf/routes
GET
/product/:id

String)

h&p://www.ﬂickr.com/photos/jameswragg/4688532009/

@rainbow:
-‐webkit-‐gradient(linear,
left
top,
left
bottom,

color-‐stop(0.00,
red),

color-‐stop(20%,
orange),

color-‐stop(25%,
yellow),

color-‐stop(30%,
yellow),

color-‐stop(45%,
green),

color-‐stop(65%,
blue),

color-‐stop(80%,
indigo),

color-‐stop(1.00,
violet));

57

“ Use HTML5 technologies
Choose a web framework that lets you
Hire or become a front-‐end expert
Use HTML ‘bricks’ instead of moulded components

60
Modern web development

■ Play is designed to work with HTML5 technologies
■ No constraints on HTML output (front-end dev-friendly)
■ UI components belong in the client, e.g. JQuery UI
■ Built-in support for improvements to CSS and JavaScript:
■ LESS http://lesscss.org/
■ CoﬀeeScript http://coﬀeescript.org/
■ Closure Compiler http://code.google.com/closure/compiler

61
Single-‐page JavaScript applicaMons

■ Server-side HTML templates are not the only game in town
■ JavaScript and mobile apps need web services
■ Play is great for building web services
■ You’ve already seen HTTP routing
■ Play has a type safe API for parsing/generating JSON
■ Play application architecture is natural ﬁt for REST
■ Functionality is not tied to view templates

62
GeneraMng a JSON response

$
curl
-‐i
http://localhost:9000/products/5010255079763

HTTP/1.1
200
OK
Content-‐Type:
application/json;
charset=utf-‐8
Content-‐Length:
88

{

"ean":5010255079763,

"name":"Paperclips
Large",

"description":"Large
Plain
Pack
of
1000"
}

63
GeneraMng a JSON response

//
Value
object
case
class
Product(ean:
Long,
name:
String,

description:
String)

//
JSON
formatter
implicit
object
ProductWrites
extends
Writes[Product]
{

def
writes(p:
Product)
=
Json.toJson(

Map(

"ean"
-‐>
Json.toJson(p.ean),

"name"
-‐>
Json.toJson(p.name),

"description"
-‐>
Json.toJson(p.description)

)

)
}

//
Controller
response
Ok(Json.toJson(product))

64
Parsing a JSON request

implicit
object
ProductReads
extends
Reads[Product]
{

def
reads(json:
JsValue)
=
Product(

(json

"ean").as[Long],

(json

"name").as[String],

(json

"description").as[String]

)
}

//
Controller
method
-‐
using
the
parse.json
body
parser
def
save(ean:
Long)
=
Action(parse.json)
{
request
=>

val
productJson
=
request.body

val
product
=
productJson.as[Product]

//
…
}

h&p://www.ﬂickr.com/photos/chris24dotca/3374782984/

66
Asynchronous HTTP programming model

■ The future of web programming is asynchronous:
■ Perform simultaneous web service requests
■ Process streams, instead of ﬁlling up memory or disk
■ Publish real-time data
■ Predictable and minimal resource consumption
■ Play’s internal architecture uses a reactive model based on
Iteratee IO (read about ‘Iteratees’ in the Play 2.0 docs)

67
Other Play 2.0 features

■ Asynchronous web programming
■ Build environment based on sbt
■ Scala REPL (irb eat your heart out)
■ Designed for easy cloud deployment, e.g. Heroku
■ Persistence - use your favourite framework
■ Ebean (Java) or Anorm (Scala) included with Play
■ Test framework integration

$
play

[info]
Loading
project
definition
from
/demo/project
[info]
Set
current
project
to
demo
(in
build
file:/
Users/pedro/Documents/code/examples-‐play/demo/)

_

_

_
__
|
|
__
_
_

_|
|
|
'_
|
|/
_'
|
||
|_|
|

__/|_|____|__
(_)
|_|

|__/

play!
2.0.1,
http://www.playframework.org

>
Type
"help"
or
"license"
for
more
information.
>
Type
"exit"
or
use
Ctrl+D
to
leave
this
console.

[demo-‐app]
$

[jfokus-‐app]
$
console
[info]
Starting
scala
interpreter...
[info]

Welcome
to
Scala
version
2.9.1.final
(Java
HotSpot(TM)

64-‐Bit
Server
VM,
Java
1.6.0_31).
Type
in
expressions
to
have
them
evaluated.
Type
:help
for
more
information.

scala>

scala>
views.html.rainbow.render
res0:
play.api.templates.Html
=

<!DOCTYPE
html>
<html>

<head>

<title>rainbow</title>

<link
rel="stylesheet"
type="text/css"
href="/
assets/colours.css">

</head>

<body>

<div
class="nyan">

<div
class="trail"></div>

<div
class="cat">insert
meme</div>

</div>

</body>
</html>

71
Play 2 books

■ Play 2 for Scala,
Peter Hilton, Erik Bakker,
Francisco Canedo
http://bit.ly/playforscala
■ Play 2 for Java, Nicolas
Leroux, Sietse de Kaper
http://bit.ly/playjava
■ Early Access (MEAP)
editions now available

@PeterHilton @PlayFramework

www.lunatech.com www.playframework.org

Play framework 2 : Peter Hilton

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