Web application development using Play Framework (with Java)

1. Web application development using Play
Framework (with Java)
Tehran JUG meeting February-2015
By: Saeed Zarinfam

2. History
 Play 1 Created By Guillaume Bort at Zengularity SA
in 2007
 Play 2 release in 2012 by Typesafe (rewrite using
Scala)
 Play 1 vs Play 2
 Part of Typesafe Activator

3. Introduction
• Inspired by Ruby on Rails and Django
• Run on JVM (use java library)
• MVC
• Stateless
• Hot code reloading (in development)
• Convention over configuration
• Lightweight
• Asynchronous and Non-blocking I/O
• Java 8 support

4. Architecture
• MVC architecture
• Netty as web server (no servlet container)
• Sbt as build tools (Ivy dependency manager)
• Stateless

5. Requirements
 Install Typesafe Activator (or sbt)

JDK 6 or later

activator new my-first-app play-java
 Open project in IDE (Eclipse and Intellij)

Run using
– command line (activator run)
– Activator console (activator)
– Activator UI (activator ui)
– Interactive Console (Only in Scala)

6. Activator UI

7. Project structure
• App
• Public
• Conf
• build.sbt
• Scala and Java
• ...

8. Route
• Scala syntax
• Optional parameters
• Reverse routing
• REST friendly

9. Controller
• Actions return Result
• Static method
• Use dependency injection (JSR 330 in Play 3)
• HTTP manipulation (body parsers)
– REST service (JSON and XML)

10. View
 Type safe template engine
 Scala Template (Twirl inspired by ASP.NET
Razor)
 Http form handling

11. Session
 Session data are not stored in the server
 Session data added to each subsequent HTTP
Request, using Cookie.
 Cookie are signed with a secret key so the
client can’t modify the cookie data or it will be
invalidated
 Use cache for sever side session data

12. Assets
 Public Assets
 WebJars
 Assets controller
 Etag

Gzip
 Caching
 Managed Assets
 CoffeeScript
 LESS CSS

Sbt-web plugins

js-engine plugin (able to execute plugins written to the Node API either
within the JVM via the excellent Trireme)

13. Hot code reloading (in
development)
 It is possible because Play is stateless and tightly integration between Play and sbt
 Classloader hierarchy manage by sbt

Tricky (You don't need JRebel)
 For each request reloader check if there's any code changes
 Compile changed codes
 remove the old application classloader
 create a new application classloader with the updated classes.
 restart application (only application, no need to restart the JVM)

14. Accessing Database
 JDBC
 JPA (2.0)
 Ebeans (default ORM)
 Database evolutions
 Connection Pool
 Transaction
 In-memory H2 database

15. Asynchronous
 Actions are asynchronous by default
 Each open connection does not need a thread
 application code should avoid blocking in
controllers

16. Other APIs

Integration with Akka

WebSockets and Comet sockets

Cache API

Internationalization

Interceptors

Filters(only in Scala)

JSON API (jackson)

XML API

Job scheduling (Using Akka)

Logging API (Logback)

17. Testing

Ready to use application stubs for test (several helper methods)

Junit

FEST assertions

Mock

Test every part of your application (router, action, controller and ...)

Testing with a browser using FluentLenium ( Selenium WebDriver
wrapper)

18. Plugins
 Several plugins
– Mail
– Open ID
– CRUD
– Security

19. Deployment
 Compile all class and assets in application
 Activator start
 Activator stage (without any dependency on Play)
 Activator dist (produces a ZIP file without any
dependency on Play)
 SBT Native Packager plugin(activator universal:package-
bin)
– MSI, OS X disk image, RPM, DEB and …
 Publishing to a Maven (or Ivy) repository

20. Scaleability
 Scale horizontally easily (using load balancer)
 Integrate with Akka clustring and remoting
features
 Asynchronous from bottom to top

21. Reactive

Play Iteratee library (Scala Library)

ReactiveMongo

22. Non-blocking
 ReturnPromise<Result>Promise<Result>
 Intensive computation will just be run on another thread
(thread pool in separate execution context ).
 The web client will be blocked while waiting for the
response, but nothing will be blocked on the server

23. ‫تشکر‬
zarinfam.s@gmail.com
http://javabyab.com