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Web application development using Play Framework (with Java)
Tehran JUG meeting February-2015By: Saeed Zarinfam
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
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
Architecture
• MVC architecture
• Netty as web server (no servlet container)
• Sbt as build tools (Ivy dependency manager)
• Stateless
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)
Activator UI
Project structure
• App
• Public
• Conf
• build.sbt
• Scala and Java
• ...
Route
• Scala syntax
• Optional parameters
• Reverse routing
• REST friendly
Controller
• Actions return Result
• Static method
• Use dependency injection (JSR 330 in Play 3)
• HTTP manipulation (body parsers)
– REST service (JSON and XML)
View
Type safe template engine Scala Template (Twirl inspired by ASP.NET
Razor) Http form handling
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
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)
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)
Accessing Database
JDBC JPA (2.0) Ebeans (default ORM) Database evolutions Connection Pool Transaction In-memory H2 database
Asynchronous
Actions are asynchronous by default Each open connection does not need a thread application code should avoid blocking in
controllers
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)
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)
Plugins
Several plugins
– Open ID
– CRUD
– Security
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
Scaleability Scale horizontally easily (using load balancer)
Integrate with Akka clustring and remoting features
Asynchronous from bottom to top
Reactive
Play Iteratee library (Scala Library) ReactiveMongo
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
