play framework in practice - devoxx 2009

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What is this play! framework

exactly?

Today, we will see how the play! framework canchange the way java web developers work

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Agenda

About the framework

Web developers != Enterprise app developers?

Looking for a simple web framework for webdevelopers

Why Play! framework is the solution

Build a simple application and learn about the play!

framework



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Speakers qualifications

Nicolas Leroux is an application developer/architect

Works for Lunatech Research since 2001 on enterprise

applicationsCo-founder of the Benelux JBUG

Co-founder of the Riviera JUG



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Are you a web developer?

Enterprise application developers tend to not claimthey are web developers

simplicity != enterprise, enterprises are complex

and require complex solutions (even if not needed)

Doing HTML != web developer

Turns out that now we are all web developers



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Is there any simple frameworks

in Java for web developers?JSF? too complex (even with Seam)

Tapestry?Struts?

...

Grails? yes but it is not Java.

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web application is an application that is accessedvia a web browser over a network such as the

Internet or an intranet.What do you mean? Building web applications iseasy enough in Java

But I thought web applications were supposed tobe desktop applications in a browser

The Play framework makes it

easier to build Web applications

http://www.devoxx.com/http://en.wikipedia.org/wiki/Intranethttp://en.wikipedia.org/wiki/Intranethttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Internethttp://en.wikipedia.org/wiki/Web_browserhttp://en.wikipedia.org/wiki/Web_browserhttp://en.wikipedia.org/wiki/Application_softwarehttp://en.wikipedia.org/wiki/Application_softwarehttp://www.devoxx.com/http://www.devoxx.com/


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Build web application should be

a simple taskClearly this is not the case in the Java ecosystem asof today

Play! philosophy: simple things should stay simplePlay! is an MVC framework

And still gives you the nice feature that Java offers

(strongly typed language, etc...)



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Play! framework in numbers

Created by Guillaume Bort in 2007 for use byZenexity

Open-sourced in 2008Version 1.0 in October 2009

Active mailing list (~20 messages per day)

Excellent documentation (~7000 lines)



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Play! is completely stateless like

the webThe session lives in a signed cookie

Easy enough to see what the application is doing

Scale without limitIt adapts to the web standard and not the opposite

RESTful services become easy to develop



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Java files are first class citizens

Like PHP, ruby, python, the source classes are whatyou are developing with.

There is no compilation or packaging steps in themiddle

No WAR file, how is that possible?

Increase development speed dramaticallyError reporting that means something (well mostof the time)



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Traditional JEE framework

Traditional web framework



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Traditional JEE framework

The play! way



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What can I do with it out of the

box?Support for business tiers (through enhanced JPA)Templates engine based on Groovy

HTTP-to-code mappingAbility to do test driven development

Plugins

ModulesWeb services



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box?Security moduleAutomatic binding

CRUDValidation

Asynchronous jobs

InternationalizationFixtures



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box?RESTFul servicesExtended JPA

Unit testsEmails

OpenID

...



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Play! scopes

Application scope

Session scope (lives in a signed cookie)

Flash scopeRequest scope

For anything else, there is the distributed cache

and it is up to you to manage it



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But the most important feature

Its FUN to work again!



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Fun != Enterprise?

It really should be fun, and Play! is bridging the gap

Play! applications can run on an application server

Play! is written in Java and supports all the existinglibraries out of the box

Play! works very well in a SOA environment

Play! has already been deployed within largeorganisations



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Its too good to be true

Lets have a go with it

Lets build ... a swag application. That should be

useful enough for this weekI propose that we see the basics of play! and then

jump into the practice



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Swag app - requirements

Should be able to create a new swag item

Display a nice thumbnail of the item

Display a nice picture of the itemVote for an item

Display the top voted items

Search for items



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Swag app - data model

We have 3 entities: Item, Picture and Comments

Item Picture

Comment

1 1

1

N



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The item class: @Entity publicclass Item extends Model {

public Float rating; public String name; public String description;

public String author;

public Integer numberOfRating; public Date createdAt;

@OneToOne(mappedBy="item", cascade=CascadeType.ALL) public Picture picture;

@OneToMany(mappedBy="item", cascade=CascadeType.ALL)

public List comments = new ArrayList();

public Item() {// left empty}

public Item(String name, String author) { this.name = name; this.numberOfRating = 0;

this.author = author; this.rating = 0f; this.createdAt = new Date();

}}



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Everything is public?

The Model portion of the play framework automatically

generates this pattern while keeping your code clean.Effectively, all public variables become instance properties.

The convention is that any public, non static, non final field

of a class is seen as a property.

See http://www.playframework.org/documentation/1.0/model#properties

http://www.playframework.org/documentation/1.0/model#http://www.playframework.org/documentation/1.0/model#http://www.playframework.org/documentation/1.0/model#http://www.playframework.org/documentation/1.0/model#http://www.playframework.org/documentation/1.0/model#http://www.playframework.org/documentation/1.0/model#http://www.playframework.org/documentation/1.0/model#http://www.playframework.org/documentation/1.0/model#http://www.devoxx.com/http://www.devoxx.com/


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Swag app - views

Name: Author: Description: Picture:



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Swag app - controller

# Routes# This file defines all application routes (Higher priority routes first)# ~~~~

# Home pageGET / Application.index

#Map static resources from the /app/public folder to the /public pathGET /public/ staticDir:public

GET /item/new Application.newItemPOST /item/new Application.createItemGET /item/new Application.newItem

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publicclass Application extends Controller {

publicstaticvoid index() {List topItems = Item.find("order by rating").fetch();render(topItems);

}

publicstaticvoid createItem(Item item, Long pictureId) {Picture pic = Picture.findById(pictureId);item.picture = pic;pic.item = item;item.save();

index();

}

publicstaticvoid newItem() {

render("/item/new.html");}

...}



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Every controller method has to be static

Extends the Controller class

Provides plenty of useful methods to render Json,xml, etc...

JPA is much simpler: for example Picture.findById()

Action chaining: automatic redirection for examplecreateItem index()



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Swag app - validation

Modify the view to display the error messages:

#{error 'item.author' /}

Or #{errors}

${error}

#{/errors}



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Swag app - fixtures

Allows you to boostrap your application with testdata

for unit / functional tests using @Before andFixtures.load

simply to have static data available using@OnApplicationStarts on a job class and Fixtures.load



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Swag app - fixtures

# Test data

Picture(catpicture):

name: ../public/images/mycat.png

file: ../public/images/mycat.png

Item(cat):

name: a cat

author: nicolas

description: a cat

picture: catpicture

...



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Swag app - adding our customtag

Create a class that extends JavaExtension publicclass CustomTags extends JavaExtensions {

publicstatic Boolean canRate(Item item) {Http.Cookie cookie = Http.Request.current().cookies.get("item_" +

item.id); return (cookie == null);

}

}

In the template: ${item.canRate()}

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Swag app - unit testing

In the tests directory. The class extends UnitTest.publicclass MyTest extends UnitTest {

@Before publicvoid setup() {

Fixtures.deleteAll();

}

@Test publicvoid createAndRetrieveItem() { // Create a new Item and save it new Item("a watch", "nicolas").save();

// Retrieve the user with bob username

Item watch = Item.find("byName", "a watch").first();

// TestassertNotNull(watch);assertEquals("nicolas", watch.author);

}



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Swag app - functional testing

In the tests directory. 2 types of functional tests.

Selenium via the templating #{selenium}

// Open the home page, and check that no error occured

open('/')waitForPageToLoad(1000)

assertNotTitle('Application error')

#{/selenium}

Java class that extends FunctionalTest @Test publicvoid testThatIndexPageWorks() {

Response response = GET("/");assertIsOk(response);

assertContentType("text/html", response);assertCharset("utf-8", response);

}



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What is next?

Scala support

More modules, more plugins through a module

repositoryBetter support for binding objects

More users

Whatever you need really!



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Thanks for your attention!

http://www.playframework.org

http://groups.google.com/group/play-framework

http://www.lunatech-research.com

http://www.zenexity.fr

http://www.playframework.org/documentation/
http://www.playframework.org/documentation/http://www.playframework.org/documentation/http://www.zenexity.fr/http://www.zenexity.fr/http://www.lunatech-research.com/http://www.lunatech-research.com/http://www.playframework.org/http://www.playframework.org/http://www.devoxx.com/http://www.devoxx.com/

play framework in practice - devoxx 2009

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