JavaFX Dependency Injection with FxContainer

JavaFX Dependency
Injection with
FxContainer

Presented by
Srikanth Shenoy
ObjectSource
Learn FxContainer in 10 minutes

Introduction
 Who am I?
 A hands-on architect
 Experienced and very knowledgeable in Java and
Java EE
 Authored a book on Struts
 Several articles on Java EE for leading journals
 Director of Enterprise Java Practice at
ObjectSource
 Creator of FxObjects and FxContainer framework

Introduction
 What is FxContainer? (Currently 1.0)
 Open source IoC container written in JavaFX.
 Meant specifically for Dependency Injection in
JavaFX applications
 Very much Spring-like
 Small footprint (< 75K)
 Sequence, Collection Support
 Mix Java and JavaFX wiring
 Learn FxContainer in 20 slides! (10 minutes)

IoC Container Landscape
 Spring
 Supports XML and Annotations based DI
 Supports Constructor & Setter Injection
 Guice
 Supports Annotations and API based DI
 Supports Constructor & Setter Injection
 PicoContainer and many more..

Why another IoC Container?
 Problems with existing IoC Containers (in the
context of JavaFX)
 JavaFX does not support annotations 
 Hence Guice leaves only programmatic DI option
 Xml DI with Spring works, but minimal jars > 1 MB
 Constructor Injection not supported in JavaFX
 Setter Injection is unnatural for JavaFX style
 JavaFX variables are written as public or public-init
 Writing setXYZ() method for variables feels artificial
 Nobody supports Sequence (the first class
JavaFX collection citizen)

Setter Injection
var finder = MovieFinder {
movieDao: MovieDao { }
}

 Dependency Injection with any other IoC
container needs a setter like this (Not Good)
public class MovieFinder {
public-init movieDao:MovieDao;
public function setMovieDao(dao:MovieDao) {
this.movieDao = dao;
}
}

Side effects of Setter Injection
 Init and Post-Init code that depends on
public-init variables will not work
 Classic Example – CustomNode.create()
 Called automatically in every UI
 Called immediately after init and post init
 No time to call setter methods
 If create() depends on objects injected by setter
injection, then it will fail !!

A Different Kind of Injection
 Constructor Injection is DURING memory
allocation
 Setter Injection is AFTER memory allocation
and object initialization
 JavaFX needs something in between the two

 We call it Init injection

 A DI based on Init Injection does not exist

 So we created it 
FxContainer is the ONLY IoC container that
provides Init Injection for JavaFX

FxContainer Core Concept
 Based on JavaFX Reflection and Init Injection
FXLocal.Context ctx = FXLocal.getContext();

//get the class
FXClassType clzType = ctx.findClass("org.fxobjects.MovieFinder");

FXObjectValue objValue = clzType.allocate(); //allocate memory

//get the variable-type
FXVarMember varMember = clzType.getVariable("movieDao");

//create the variable-value
FXValue varValue = ctx.mirrorOf(Some String or object);

//initialize the variable. Basis for FxContainer Init Injection

objValue.initVar(varMember, varValue);
objValue.initialize(); //Finally initialize the object

FxContainer Overview
 Uses Setter Injection for Java objects
 Uses Init Injection for JavaFX objects
 Can mix both Java and JavaFX objects
 Java objects can hold references to JavaFX
objects via interfaces
 Very Spring Like in configuration
 Powerful, Lightweight and Easy to use

FxContainer: Simple
Dependency Injection
<fxcontainer>

<fxobject name="movieFinder"
class="org.fxobjects.samples.fxcontainer.MovieFinderImpl">
<property name="someVar" value="Some random value"/>
<property name="javaHelper" ref="javaHelperObj"/>
<property name="jfxHelper" ref="jfxHelperVarObj"/>
</fxobject>

<fxobject name="movieLister"
class="org.fxobjects.samples.fxcontainer.MovieLister">
<property name="finder" ref="movieFinder"/>
</fxobject>

</fxcontainer>

FxContainer: Import XML
 Good for organizing large XML into smaller
logical chunks
<fxcontainer>

<import resource="/org/fxobjects/samples/abc.xml"/>

<property name="someVar" value="Some random value"/>
<property name="javaHelper" ref="javaHelperObj"/>
</fxobject>

</fxcontainer>

FxContainer: Import Properties
 Good for Spring style ${ } substitutions
<fxcontainer>

<import resource="/org/fxobjects/samples/abc.properties"/>

<property name="someVar" value=“${svr1Name} is ${svr1Status}"/>
<property name="javaHelper" ref=“${helperObj}"/>
</fxobject>

</fxcontainer>

 value and ref can be substituted

FxContainer: Wired Object
Attributes
 Wired Objects in FxContainer have the following defaults
(can be overridden)
 Every wired object is singleton
 Every wired object is lazily initialized (i.e on demand)
 There is no order of initialization (Although load order can be
specified for eagerly loaded objects)
 Init-method is called after all properties are injected
<fxcontainer>
class="org.fxobjects.samples.fxcontainer.MovieFinderImpl“ lazy-
init=“false” load-order=“1” init-method=“someMethod”>
..
</fxobject>
</fxcontainer>

FxContainer: Sequences
<fxcontainer>
<property name="movieCodes">  Primitive Sequence
<sequence>
<entry value=“1" />
<entry value="2" />
</sequence>
</property>
<property name="movies">  Object Sequence
<sequence>
<entry ref="movie1"/>
</sequence>
</property>
</fxobject>
</fxcontainer>

FxContainer: Lists and Sets
<fxcontainer>
<property name="movieList">  Object LIST
<list> (or <set>)
</list>
</property>
<property name="movieCodes">  Primitive LIST
<list valueClass=“java.lang.Integer”>
<entry value=“1" />
<entry value="2" />
</list>
</property>
</fxobject>
</fxcontainer>

FxObjects Lists and Sets
(Contd.)
 Lists and Sets have to be initialized in their
parents with a new …..();
 valueClass attribute
 Optional in most cases
 Reason: One cannot tell from the xml value
attributed if a list is Integer, String, BigDecimal
etc.
 Needed for Java and JavaFX objects when
 value attribute is specified in xml AND
 List is not parameterized (always the case in JavaFX)

FxContainer: Maps
<fxcontainer>
<property name="movieMap">  Object MAP
<map>
<entry keyRef=“stage1” valueRef="movie1"/>
</map>
</property>
<property name="movieCodes">  Primitive MAP
<map keyClass=“java.lang.String”
valueClass=“java.lang.Integer”>
<entry key=“Terminator 1” value=“1" />
<entry value=“Terminator 2" />
</map>
</property>
</fxobject>
</fxcontainer>
keyClass and valueClass are needed for Maps in JavaFX with key
and value specified. (since they cannot be parameterized) and

FxContainer: Startup
 Spring Like
var loader = ClasspathXmlContainerLoader {
resourceLocation: "/org/fxobjects/samples/my.xml“
}
var container:FxContainer = loader.load();
var mvLister:MovieLister =
container.getFxObject("movieLister") as MovieLister;

 FxContainer can be used the IoC container
with FxObjects or any other JavaFX
application independently
 Just include 2 jars – fxcontainer.jar and
fxobjects-util.jar in classpath

FxObjects & FxContainer:
Roadmap

Links
 Project site – https://fxobjects/dev.java.net
 FxContainer is a subproject of FxObjects
 Not a single person open source project
 FxObjects and FxContainer developed and supported
by ObjectSource (http://www.objectsource.com)
 Download, use, extend, redistribute, OEM
 Discussion Forums on project site
 Participation welcome
 Post ideas, questions, concerns, comments
 Contribute code

JavaFX Dependency Injection with FxContainer

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