Java Everywhere: Write Once run Anywhere with DukeScript

273 Pages·2015·7.69 MB·English

by  Anton Epple

Java everywhere
Write Once run Anywhere with DukeScript

Anton Epple

This book is for sale at http://leanpub.com/dukescript
This version was published on 2015-12-28
*
This is a Leanpub book. Leanpub empowers authors and publishers with the
Lean Publishing process. Lean Publishing is the act of publishing an in-progress
ebook using lightweight tools and many iterations to get reader feedback, pivot
until you have the right book and build traction once you do.
*

© 2015 Anton Epple
Table of Contents

Preface
About this book
History
How it works
Getting started!
Prerequisites
Developing DukeScript apps with the NetBeans Plugin
Creating DukeScript apps with Eclipse
Using Maven to create a DukeScript project
The Generated Projects
Understanding the sample application
Running the application
The View
Binding the View to the Model
The Model
Putting it all together
Debugging a DukeScript application
Debugging Java Code
Visual Debugging
Debugging on Android Devices
Debugging on iOS Devices and Emulators
Debugging JavaScript Code
Debugging JavaScript with firebug-lite
Summary
Using the Knockout API
Model, View, ViewModel (MVVM)
The Model
The ViewModel
The View
Defining the ViewModel
Summary
DukeScript, JSON and the REST
Creating the project
Running the application
The client application
Code sharing
Parsing JSON
Summary
Workshop: DukeScript Twitter Client
Prerequisites
Set up the project
DukeScript, JSON and the REST
Creating the ViewModel
A model for parsing JSON results
Create a JSON Endpoint
Adding Functions for the UI
Observing Property changes
Initializing the model
The View
Separating View and ViewModel in practice
The state of UI Development
The Setup
Finding the right Designer
Working with the design
The result
Responsive Design with CSS
New CSS3 units vh and vw
Testing
Unit Tests
Test Driven Development means “Test first”
Is your UI Toolkit Test friendly?
DukeScript to the rescue
A little example - Unit Testing a viewmodel
Unit testing server communication
@OnReceive with Plain Text
Type-safe Access to Received JSON Data
Dealing with JSON Arrays
Summary
Deploying to the App Stores
Deploying to the Google App store
Deploying to the Apple Store
Summary
Creating a new API
Some examples
HTML5 Canvas
The @JavaScriptBody Annotation
The @JavaScriptResource Annotation
Summary
Dear Reader,
Preface
For many years, Java Swing enabled developers to write applications that could
run on any operating system. That all came to an end with the arrival of smart
phones, tablets, and embedded computers. In the enterprise, the desktop
dominated for many years. In the meantime, however, almost every IT project
includes plans for a future where the application will need to be ported to mobile
platforms. Building native applications for all platforms requires special skills
and is expensive in terms of both maintenance and development.
We wanted to simplify this problem and make cross-platform development
available for everyone again. That’s why we developed DukeScript. In this book
you will learn how to use DukeScript and develop Java applications that run on a
lot of different devices.
About this book
This is a book to help you with your project. If you’re an absolute DukeScript
newbie, that’s perfect. The book starts by explaining the core concepts and then
immediately jumps to practical exercises. We’ll go through our sample
applications and inspect how they work. Along the way I’ll explain the basic
workings and ideas behind the APIs. There are also some more chapters
explaining just the concepts themselves especially for our most important APIs,
but most of the time they are accompanied by lots of workshops and code
examples. Thereby you’ll get a bit of repetition which is said to be beneficial for
learning and you can put your newly acquired knowledge to a practical test.
That’s the basic idea behind this book. I hope you’ll find it useful.
What this book is not
This book is not a reference book. You will find some nice structured
information on the Knockout API, but you will not find all the APIs documented
in great detail. In this book I try to explain how things work together and give
practical advice on how to use it, for a detailed reference you can use the
excellent API documentation. We’re really trying to make API Docs as helpful
as possible.
Improving this book
This is a living book. That means that new chapters will be added and content
will be updated. Once you’ve bought the book you’ll get these updates for free
as long as the book exists. If I find any errors I’ll try to fix them in a timely
manner, and if you spot any errors, let me know! It also means that if you want
more detail on something, or if you miss something, you can tell me, and I can
try to include it, so together we can make our book even better.
History
For many years Jaroslav Tulach, the original architect and founder of NetBeans,
and I gave a short lecture on API design together with Thomas Wuerthinger at
the Johannes-Keppler University of Linz. We always brought some of our pet
projects, and in the evenings we typically ended up in some pub drinking beer
and hacking until we were thrown out.
In 2012 Jaroslav was really frustrated by Javas stagnation on the client. Oracle
declared that Swing was no longer developed, Applets were dead, and JavaFX a
half-hearted approach to create a successor. While it was obvious that Java was
the better language for building tooling and large scale applications, JavaScript
and web technologies were basically the only way to do cross platform
development.
Jaroslav was looking for a way to keep Java relevant in the browser. His solution
was bck2brwsr, a Java Virtual Machine running in the browser without a Plugin.
The idea was to support a small part of Javas APIs to make it a lean JVM and
use HTML as the view technology.
I brought a little game engine that year using JavaFX Canvas as rendering
technology. And since HTML5 Canvas has a very similar API, I decided to
create a Canvas API for bck2brwsr that could render either to a HTML5 Canvas
or to a JavaFX Canvas. That way all my games would run in the browser.
A little later bck2brwsr and the Canvas API were even used by a group in Oracle
to create a proptotype of JavaFX in the browser. Unfortunately all the efforts to
port JavaFX to mobile platforms and the Browser inside Oracle were canceled so
this work never got released, but we were really encouraged by the performance
of our work.
Over time the focus changed from the browser JVM to the idea of having
Over time the focus changed from the browser JVM to the idea of having
HTML5 as a view technology instead of Swing or JavaFX. KnockoutJS, one of
the most popular JavaScript libraries turned out to be really great for separating
the View from the rest of the application. And it soon became clear that this was
really useful also in Swing or JavaFX applications, because it allowed for a very
clean and testable architecture. So Jaroslav adapted the bck2brwsr APIs for his
work on NetBeans and created the HTML/Java APIs, which are now at the core
of DukeScript.
For me it was the first time I came into contact with the Model View
ViewModel pattern and I was immediately hooked. The way Jaroslav had
designed the HTML/Java APIs they could also be used outside of NetBeans.
And he had created Service Provider Interfaces that made it relatively easy to
port the technology to new platforms.
All you need is a very basic JVM and a modern HTML5-renderer component.
This was the start of DukeScript. I had coined this term because the inventors
JavaScript had abused the term “Java” to benefit from Javas popularity in the
early years. So I waneted to point out that we had put real Java represented by
“Duke” the Java mascot into JavaScript. I started using this term for the whole
ecosystem we created to build a community, and port DukeScript to other
platforms, build tools and Maven archetypes and develop additional APIs. So
it’s entirely my fault that a lot of people think that this is just another Scripting
language when they first get into contact, and I hereby appologise.
How it works
I already mentioned that the basic requirement is a JVM and a HTML5 renderer
component.
Install DukeScript Wizard
On the Desktop we use Oracles HotSpot Virtual Machine and as a HTML-
Renderer we use the JavaFX WebView. In the Browser we use the bck2brwsr
VM or TeaVM, and the Browser itself is the HTML-Renderer. Here’s a little
table to show what we use on supported platforms:
OS
Java VM HTML5 Renderer
Platform
OS X,
Windows, Oracle Hotspot JavaFX WebView
Linux
iOS RoboVM NSObject.UIResponder.UiView.UIWebView
Android Dalvik/ART android.webkit.WebView
Browser bck2brwsr/TeaVM Chrome, Firefox, IE…
OpenJDK/JamVM/Java
Embedded Chromium
SE Embedded
This architecture made it really easy to port to different platforms, and we can
relatively easy adapt to new platforms if there is demand. But now without
further ado, let’s start coding DukeScript!
Getting started!
It’s time to get your hands dirty. In this chapter you’ll learn everything you need
to create your first DukeScript application. First I’ll show you how to install and
use the NetBeans Plugin. And you’ll also learn how to use the Maven
Archetypes directly. This is important if you’re required to use an IDE other than
NetBeans. I’ll also show you some tricks how to best integrate DukeScript
Development with Eclipse. After this chapter you’ll know anything you need to
create a new DukeScript application.
Prerequisites
For developing DukeScript applications you need at least JDK 7 and Maven
3.2.5. The best IDE for developing DukeScipt is NetBeans which provides some
extra features like hot swapping of code and visual DOM Inspection, but you can
also use Eclipse. For developing Android applications you need to install the
Android SDK. Initially the SDK doesn’t include all the required parts. You also
need to add some SDK packages. You should at least download the latest tools
and Android platform 19. To do so, launch the SDK Manager.
Now open the Tools directory and select “Android SDK Tools”, “Android SDK
Platform-tools”, and “Android SDK Build-tools (highest version)”. Now Open
the first Android 19.0 folder and select “SDK Platform”. If you have no real
Android device, you should also download a system image for the emulator,
such as ARM EABI v7a System Image. For building for iOS you need XCode 6
and a Mac running OS X 10.9 or later.
Developing DukeScript apps with the NetBeans Plugin
The easiest way to develop, debug and deploy DukeScript applications is to use
NetBeans and it’s DukeScript Plugin. There are a lot of extra features we’ve put
into that, so we strongly suggest to use it. Throughout the book we’ll be using
NetBeans for most tasks. Still, if you don’t want, or aren’t allowed to use it, you
can still use our Maven Archetypes. In that case you can skip this section.