Complete Dojo

Dojo Tutorial

Girish Srivastava
girish.srivastava@vtindia.net
1 5/19/2012

Objective
 In this tutorial, we will learn everything about the dojo. After
completing the tutorial you will be able to understand about Dojo
framework.
 This Dojo tutorial covers:

2 5/19/2012

Introduction to Dojo
 What is Dojo?
 Dojo is JavaScript framework released as open source
software. This JavaScript toolkit provides many components to
develop rich internet applications.
 You can use Dojo toolkit to develop dynamic web applications.
Dojo toolkit will put life in your web application and turn it
into highly interactive application.You can turn your web
application into desktop like web application.
 Dojo offers many widgets, utilities and ajax libraries to develop
your application.
 Dojo is released under BSD or AFL license
 Dojo is free and can be used to develop free or commercial
3 application. 5/19/2012

Features of Dojo
 Dojo is based on HTML and JavaScript, so its easy for the developers to learn it
fast.
 There is no requirement of learning new programming language. Just HTML and
JavaScript knowledge if sufficient.
 Dojo provides higher abstraction layer to the programmer. So, it helps the
programmers to develop powerful functions very easily.
 Dojo has already invented the wheels for the programmers and now programmers
just have to use the Dojo api into their application
 Here is the list of components that comes along with Dojo framework:
 DOJO Tree
 DOJO Button
 DOJO Calendar control
 DOJO Grid
 DOJO List box
 and many more..
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DOJO Core

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What Is Dijit?

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What is a widget
 A widget is an object, that contains not just logic, but also a
way to be presented on the screen
 The way a widget is presented is the widget’s template

 Widget can contain other widgets

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General widgets
 General purpose widgets that are used to make a web page
more “application-like”
 Menu
 Dialogs
 Inline editing
 Toolbar
 ProgressBar
 Tree – that can be connected to data source
 Rich text editor – with plugins architecture to configure the
editor’s functions
There are many more general widgets in dojoX
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14

What makes a widget
 A widget is composed of two resources
 A .js file that contains the logic of the widget
 An html snippet that contains the way the widget is presented
 This resource is called the widget’s template
 The html code itself can be in another file or inlined in the .js file

This allows later on to perform runtime optimizations, by placing the
template in a separate file during development time, and inline it as part
of the build process

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15

Benefits of Dojo Framework
 Dojo toolkit provides many widgets to develop the UI for web
applications.
 Dojo is one of the robust ajax framework that can be used to develop
enterprise grade application.
 Following are the benefits of Dojo.
 Associative arrays
 Loosely typed variables
 Regular expressions
 Objects and classes
 Highly evolved date, math, and string libraries
 W3C DOM support in the Dojo
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Disadvantages of Dojo
 Developer depends on the browser support for the Dojo
 There is no way to hide the Dojo code in case of commercial
application

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JQuery versus Dojo versus YUI
•JQuery
 Pros:
- JQuery is the most popular one of them all.
- It is very easy to use and to understand.
- The core library is only 15Kb in size.
- Their statement is: ‘The Write Less, Do More, Javascript
Library’.
 Cons:
- Hard to use with object oriented programming
- JQuery is a library

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•YUI(TheYahoo! User Interface Library)
 Pros:
- It is developed by Yahoo
- Fully documented, with a great API browser
- Very consistent and reliable
- Also contains unit testing framework
- YUI is a framework
 Cons:
- Heavy page weight
- Very few utility or helper functions/methods
- Lacks the use of chaining methods together

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• Dojo Toolkit
 Pros:
- Debug your code in Firebug
- Dojo integrated in Zend Framework
- Hierarchical package system speeds loading
- Dojo is a framework
 Cons:
- Dojo fails in online documentation

When we compare these 3 libraries/frameworks, I found the
following which was quite useful.
http://selectors.turnwheel.com/slickspeed.php
20 5/19/2012

 Based on these results, we can conclude that YUI is the slowest one. This is
also the reason why we didn’t chose for YUI. Dojo and JQuery scores the
best.
 Knowing that JQuery is the easiest to use and immense popular, Dojo has its
advantage of being integrated in Zend Framework. Also, the difference in
being a library or framework counts.
- A library is about reusable functionalities, but a framework is about
reusable behaviours
- A library is something you call/inherit from your code, but framework is
something that calls your code or provide services for your code
- A library is a collection of components and classes, where framework is
how abstract classes and components interact with each others
 Dojo is a framework and JQuery a library.
 JQuery is good for small websites where you want to achieve a ‘WOW’
factor in relative short time.
 But when you are building an application, you need a robust framework
where you can integrate your own codes.
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Loading Dojo ToolKit…

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Install Dojo
 Downloading Dojo
 You can download the latest version of Dojo from its official
site http://dojotoolkit.org/.
 Download the Dojo toolkit directly
from http://dojotoolkit.org/download.

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Themes and Theming
 Dijit Themes lend a consistent look and feel to widgets.
 Themes are collections of images (icons and background images) and
CSS files that bring a common visual style (font, color, texture,
layout, animation, etc.) to all the widgets.
 Using a Theme
 To include a given theme on your page or application, first include
the themeName.css file (one of claro.css, tundra.css, nihilo.css, or soria.css):
 <link rel="stylesheet" href="dojo/dijit/themes/claro/claro.css" />
 Then, add a theme class name to the parent <body> element, like:
 <body class="claro">
 It is recommended you include the theme CSS file before dojo.js to avoid any
potential race conditions where widgets start rendering before the theme has
finished loading. Thus, putting it all together:

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Example
 <html>
<head>
<title>Hello, Dijit</title>
<link rel="stylesheet"
href=“dojocore/dijit/themes/claro/claro.css">
<script src="lib/dojo/dojo.js"></script>
<script type="text/javascript">
dojo.require("dijit.Dialog");
</script>
</head>
<body class="claro">
<h1>Hello, Dijit</h1>
</body>
</html>
32 http://dojotoolkit.org/reference-guide/1.7/dijit/themes.html 5/19/2012

Dojo Hello World
<html>
<head>
<title>Hello World</title>
<script type="text/JavaScript" src=“dojoroot/dojo/dojo.js"
djConfig="parseOnLoad: true"> </script>
<style type="text/css">
@import "dojoroot/dijit/themes/tundra/tundra.css";
@import "dojoroot/dojo/resources/dojo.css";
</style>
<script type="text/JavaScript">
dojo.require("dijit.form.Button");
</script>
</head>
<body class="tundra">
<button dojoType="dijit.form.Button" id="helloButton"> Hello World
<script type="dojo/method" event="onClick">
alert("Hello Dojo.");
</script>
</button>
</body>
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 The dojo.js file is the main component in the Dojo toolkit. You can
use Dojo by including this file in your page.
 The djConfig attribute is used for configuring the Dojo runtime.
 We want to use Dijit's button widget, so you must include the Dijit
style sheet, as shown here:
<style type="text/css">
@import "dojoroot/dijit/themes/tundra/tundra.css";
</style>
 Dijit allows you to choose a theme to use. The default theme is tundra,
which we use in our sample code by including tundra.css.

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 Dojo uses the concept of modules, which are similar to Java packages.
Before you use functionality from a particular package, you must
include that package in your page. The dojo.require() call -- similar
to Java's import statement -- is used for importing a Dojo module:
o <script type="text/JavaScript">
o dojo.require("dijit.form.Button");
o </script>
 The line dojo.require("dijit.form.Button") tells Dojo to load
the dijit.form.Button class on your page.
 To use any widget in a page, you must import its code using
dojo.require().

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 You can use a Dijit widget by using the same markup as that of the
normal HTML element. The only difference is that you must add
the dojoType attribute indicating name of the Dijit widget that you
want to use:
<button dojoType="dijit.form.Button" id="helloButton">
Hello World
<script type="dojo/method" event="onClick">
alert("Hello Dojo.");
</script> </button>

 Like This we can create can create different different examples.
 CheckBox …
 ComboBox…
 RadioButton… etc.

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Configuring the Dojo runtime
 Dojo allows you to configure the runtime using the djConfig object.
 The default value of parseOnLoad is false. If you do not set it to
true, by default, system will not create any widgets.
 Dojo creates the djConfig object when the framework initializes --
that is, when Dojo.js loads.
 If you want to make any changes in djConfig, you should do so
before dojo.js is loaded.
 Any changes that you make in djConfig are ignored after dojo.js is
loaded.
 Here, we set the parseOnLoad property to true. This causes Dojo to
attach an onload event handler for the body. From that event handler,
Dojo traverses the DOM tree and instantiates the widgets whenever a
widget markup is located.

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 The easiest and most commonly used approach is to add the
djConfig attribute to the <script> element that refers to
dojo.js:
<script type="text/JavaScript"
src=“dojocore/dojo/dojo.js"
djConfig="parseOnLoad: true, isDebug: true“>
</script>

isDebug: This flag turns debugging on or off.
Its default value is false. When you turn this flag on, Firefox
generates extended debugging information in Firebug.
If you're using some other browser, it includes the Firebug
Lite script files in the page and starts displaying the Firebug
Lite console.
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•Event Handling

•Add Buttons
Add a new dojo.require() statement to include the code for the
dijit.form.Button widget.
<script type="text/javascript">
</script>
Just above the line:
</body>
Add:
<br />
<button dojoType="dijit.form.Button">OK</button>
<button dojoType="dijit.form.Button">Cancel</button>

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Understanding Dojo's Event Handling
 Event handling works somewhat differently in Dojo than regular
DOM. First, let's recap DOM's event handling scheme.
 For a regular button element, you will register an onclick event
handler as follows:
 <button onclick="showEventStd(this, event);">OK</button>

 The "this" and "event" keywords tell the browser to supply the
element and the event object as parameters to the handler function.
The handler function looks something like this:
function showEventStd(theElement, theEvent) {
alert("Event " + theEvent.type + " for element " + theElement.nodeName);
}

40 5/19/2012

Cont…
 In Dojo, there are two main differences.
1. A Dojo button's onclick attribute takes the name of the event
handler method.You don't actually call the method like you do for a
regular DOM button.
2. Second, the event handler method gets only one parameter –
the Event object.
 Let's have a look at an example. The event handler is registered as
follows:
<button dojoType="dijit.form.Button" onclick="showEvent">OK</button>
The event handler method looks like this:
function showEvent(theEvent) {
alert("Event " + theEvent.type);
}

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Continue with…

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JavaScript Object Oriented Feature
 <html>
<head>
<Script language="JavaScript">
function MyClass()
{
this.myData = 10;
this.myString = "my frist program";
}
var myClassObj1 = new MyClass();
var myClassObj2 = new MyClass();
myClassObj1.myData = 20;
myClassObj1.myString = "Obj1: my second program";
myClassObj2.myData = 30;
myClassObj2.myString = "Obj2: last program";
alert( myClassObj1.myData );
alert( myClassObj1.myString );
alert( myClassObj2.myData );
alert( myClassObj2.myString );
</script>
</head>
</body>
</html>
44 5/19/2012

Object-Oriented Programming

 The Object Oriented programming is a computer programming
paradigm.
 Object Oriented programming is that computer program may be
seen as comprising a collection of individual units and objects, that is
on each other, as opposed to a traditional view in which a program
may be seen as a collection of functions or procedures, or simply as a
list of instructions to the computer.
 Each object is capable of receiving messages, processing data, and
sending messages to other objects.

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 Object:
 The Object an instance of a class and object is the run-time manifestation of a
particular exemplar of a class.
 Each object has own data, though the code within a class a subclass or an
object may be shared for economy.
 Encapsulation
 The Object-Oriented program using the myclass as defined permits accessibility of
its internal data representation as well as this methods and variable names global in
scope increasing the risk of name collisions.
 The Object-Oriented program Encapsulation supports data hiding and the concept
of viewing objects as self-contained entities providing services to consumers.
 Encapsulation is a modern programming languages of the principle of information
hiding itself in a number of ways, including encapsulation and polymorphism.

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Prototype-based OOP
 JavaScript implements a type of object-oriented programming
different to that used in Java™ code.
 Whereas Java programming is based on a class-based OOP model,
JavaScript is based on a class-less-based OOP model commonly
known asprototype-based object-orientation.
 Rather than defining a set of class templates from which objects are
created, objects are simply declared when needed.
 When anobject needs to inherit features from another object, it can
simply clone the features of a prototype object.
 One of the key advantages of prototypal OOP is that an object
prototype can be modified at run time, meaning that the definition of
the structure of objects is not strict.

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A basic object prototype in JavaScript
function Car() { }
var myCar = new Car();
console.log(myCar);
 This should produce the following output in the console log:
Object {}.
 Defining a member variable in your object
function Car() { }
Car.prototype.current_speed = 0;
console.log(myCar);
 This time, the console log will output something a bit more
interesting: Object{ current_speed=0 }.
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Adding a method to the prototype
function Car() { }
Car.prototype.current_speed = 0;
Car.prototype.accelerate = function(increment)
{
this.current_speed += increment;
}
myCar.accelerate(30);
myCar.accelerate(20);
console.log(myCar);
 The console output should produce the following: Object {
current_speed=50 }.

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Example
 <html>
<head>
<Script language="JavaScript">
function MyClass()
{
var m_data = 15;
var m_text = "indian";
this.SetData = SetData;
this.SetText = SetText;
this.ShowData = DisplayData;
this.ShowText = DisplayText;
function DisplayData()
{
alert( m_data );
}
function DisplayText()
{
alert( m_text );
return;
}
function SetData( myVal )
{
m_data = myVal;
}

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Example Cont…
function SetText( myText )
{
m_text = myText;
}
}
var Obj1 = new MyClass();
var Obj2 = new MyClass();
Obj1.SetData( 30 );
Obj1.SetText( "Obj1: my cuntry" );
Obj2.SetData( 60 );
Obj2.SetText( "Obj2: my first javaScript progarm" );
Obj1.ShowData();
Obj1.ShowText();
Obj2.ShowData();
Obj2.ShowText();
</script>
</head>
</body>
</html>
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Functions

 functions are objects
 they have properties
 they have methods
 can be copied, deleted, augmented...
 special feature: invokable

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Functions

function boo(what) {
return what;
}
 or
var boo = function(what) {
return what;
};

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Functions

function boo(what) {
return what;
}
 or
var boo = function bootoo(what) {
return what;
};

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Return value
 all functions return a value
 if they don't explicitly, they return undefined
implicitly
 functions can return other functions

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Constructors
 when invoked with new, functions return an object known
as this
 you have a chance of modifying this before it's returned
 you can also return some other object

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Constructor functions

var Person = function(name) {
this.name = name;
this.speaks = 'fr';
this.say = function() {
return "Je m'appelle " +
this.name;
};
};

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An object created with constructor
>>>
var julien = new Person("Julien");
>>>
julien.say();
"Je m'appelle Julien"

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prototype
 a property of the function objects

>>> var boo = function(){};
>>> typeof boo.prototype
"object"

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Prototypes can be augmented
>>> boo.prototype.a = 1;
>>> boo.prototype.sayAh =
function(){};

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Prototypes can be overwritten
>>> boo.prototype = {a: 1, b: 2};

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How is the prototype used?

 when a function is invoked as a constructor

var Person = function(name) {
this.name = name;
};
Person.prototype.say = function() {
return this.name;
}

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How is the prototype used?

>>> var dude = new Person('dude');
>>> dude.name;
"dude"
>>> dude.say();
"dude"

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Own properties vs. prototype’s
>>> dude.hasOwnProperty('name');
true
>>> dude.hasOwnProperty('say');
false

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The prototype chain

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It’s alive!
>>> typeof dude.numlegs
"undefined"
>>> Person.prototype.numlegs = 2;
>>> dude.numlegs
2

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Inheritance

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Inheritance via the prototype
>>> var Dad = function()
{
this.family = “Rahul";
};
>>> var Kid = function(){};
>>> Kid.prototype = new Dad();
>>> var billy = new Kid();
>>> billy.family
“Rahul"

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Inherit one more time
>>> var GrandKid = function(){};
>>> GrandKid.prototype = billy;
>>> var jill = new GrandKid();
>>> jill.family
“Rahul"

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Inheritance…
>>> jill.hasOwnProperty('family')
false
>>> jill.__proto__.hasOwnProperty('family')
false
>>> jill.__proto__.__proto__.hasOwnProperty('family')
true

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Object-orientation in Dojo

 One of the lesser-known facts about JavaScript is that it is an object-
oriented language.
 However, it is a prototype-based object-oriented language that
doesn't have the same structure as class-based languages such as Java.
 Dojo provides functionality to simulate class-based object-oriented
concepts such as declaring classes, constructors, and inheritance.
 In the background, it takes care of things like prototyping,
inheritance, and various procedures that JavaScript requires.

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Working with classes
 Dojo provides a dojo.declare() method that you should
use to declare a new class. It accepts the following
arguments:
 A string representing the name of the class that you want to
declare.
 The name of the superclass or array of names of the
superclasses that you want this class to inherit from. (I'll talk
more about multiple inheritance later.)
 A hashmap of properties for the class. The properties
represent both instance variables and member function of
this class.

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Cont…
 Declaring a class
• dojo.declare("custom.javaworld.Worker",null,{
firstName: "",
lastName: "",
work: function(){
console.log("Working");
}
});
var johnDoe = new custom.javaworld.Worker();
johnDoe.work();
johnDoe.lastName ="Doe";
console.log("Last Name " + johnDoePerson.lastName);

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Cont…
 Here the dojo.declare() method's first argument is
custom.javaworld.Worker -- the name of the class we want to
declare. The method's second argument is null because we don't want
to inherit this class from any other class. The third argument is a
hashmap, in which work is the property's name and its value is a
function. We thereby define a work() member function for
the Worker class.
 Once the custom.javaworld.Worker class is declared, you can
create a new object instance of it by calling new
custom.javaworld.Worker().
 Then you can start calling the new object's methods or assign values
to its member variables.

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Constructors
 A constructor allows you to initialize every object of a class by executing
code whenever a new instance of the class is created.
 Adding a constructor
• dojo.declare("custom.javaworld.Worker",null,{
firstName: "",
lastName: "",
constructor: function(fName, lName){
console.debug("Constructor of com.javaworld.Worker called");
this.firstName = fName; this.lastName = lName;
},
work: function(){
console.log("Working");
}
});
var johnDoe = new com.javaworld.Worker("John","Doe");
console.log("First Name " + johnDoe.firstName);
console.log("Last Name " + johnDoe.lastName);
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Inheritance
 The ability to extend other classes is one of the basic features of
object-oriented programming.
 Dojo handles all the requirements for setting up an inheritance
chain.
 For example, when you create an instance of a class, Dojo calls the
constructor of its superclass before calling constructor of the child
class.
 Also, if you add a method to the child class with same name as that of
the superclass, then the method in the child class overrides the
method in the superclass.

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Extending a class
 creates a custom.javaworld.ITWorker class that
extends custom.javaworld.Worker.
dojo.declare("custom.javaworld.ITWorker",custom.javaworld.Worker,{
console.debug("Constructor of com.javaworld.ITWorker");
},
work: function(){
this.inherited(arguments);
console.log("Writing Code");
}
});
var johnDoe = new com.javaworld.ITWorker("John","Doe");
johnDoe.work();
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Cont…
 Because we want ITWorker to extend the Worker class, the above
code passes the custom.javaworld.Worker class as the second
argument when declaring the ITWorker class.
 Now when you create a new instance of ITWorker using
the new operator, Dojo first invokes the constructor
of Worker class. Also, the ITWorker class's work() method
overrides the Worker class's work() method.
 The .inherited() construct to invoke an inherited method of the
superclass.
 Here when you call the ITWorker class's work() method, it first
invokes the Worker class's work() method, which prints
"Working" on the console then prints "Writing Code" on the
console.
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Multiple inheritance
 Dojo allows a class to inherit from multiple classes.
 Create a PartTimeMusician class that inherits from both
ITWorker and Musician.
dojo.declare("com.javaworld.Musician",null,{
console.debug("Constructor of com.javaworld.Musician");
},
playMusic: function(){
console.log("Playing Music");
}
});
dojo.declare("com.javaworld.PartTimeMusician",
[com.javaworld.ITWorker,com.javaworld.Musician],{
console.debug("Constructor of com.javaworld.PartTimeMusician");
}
});
var johnDoe = new com.javaworld.PartTimeMusician("John","Doe");
johnDoe.work();
johnDoe.playMusic();
79 5/19/2012

Cont…
 we pass an array of ITWorker and Musician as the second
argument to the dojo.declare() method while declaring
the PartTimeMusician class.
 Now when you execute this code it will generate output like this:
• Constructor of com.javaworld.Worker called
• Constructor of com.javaworld.ITWorker
• Constructor of com.javaworld.Musician
• Constructor of com.javaworld.PartTimeMusician
• Working
• Writing Code
• Playing Music
As you can see, the constructor of the Worker class, which is the parent of
the ITWorker class, is invoked first, followed by the constructor
of ITWorker.
The constructor of ITWorker is called before Musician's constructor
because, while declaring the PartTimeMusician class, we passed an array
of superclasses in which ITWorker was the first argument
and Musician was the second argument.
80 http://dojotoolkit.org/documentation/tutorials/1.6/declare/ 5/19/2012

Overriding methods
 A method of a superclass can be extended by declaring an attribute
with the same name.
 There is no concept of overloading, as JavaScript ignores any
unexpected arguments and substitutes null for any that are missing.
 In Java code, to invoke the overridden method you call the method on
super (that is, super().method Name(arg1, arg1);), but in Dojo you
use the inherited method (this.inherited(arguments);)
 The Following Example shows two classes declared,
where child extends parent, overriding its helloWorld method, but
calls inherited to access the function of parent.

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Example
 Invoking superclass method in Dojo
dojo.declare( "parent", null,
{
helloWorld : function()
{
console.log("parent says 'hello world'");
}
} );
dojo.declare( "child", parent,
{
helloWorld : function()
{
this.inherited(arguments); // Call superclass method...
console.log("child says 'hello world'");
}
} );
var child = new child();
child.helloWorld(); http://www.ibm.com/developerworks/web/librar
82 y/wa-aj-dojo/ 5/19/2012

Remote Scripting with XHR

 Remote scripting is the process of communicating with a server
from a client-side script without requiring a page reload.

•Each methods of remote scripting has advantages and
disadvantages. Although XHR began life as a Microsoft-only
technology, it is now available in all modern browsers.

83 5/19/2012

Cont…

 XHR allows for full control of the HTTP transaction (URL,
headers, content), can use any HTTP method (GET, POST, PUT,
DELETE), and can be executed both synchronously and
asynchronously.
 because of the same-origin policy, an XHR object cannot
communicate with a server that resides at a different origin than the
document that contains the script making the service request.

84 5/19/2012

Making an XMLHttpRequest
 Most browsers provide a XMLHttpRequest object that allows you to
make an asynchronous request to the server and get a response
without refreshing the whole page.
 But if you try to use the XMLHttpRequest object directly without
using a JavaScript framework such as Dojo, you'll run into problems
such as memory leaks and divergent, browser-specific APIs.
 The Dojo toolkit simplifies the use of XMLHttpRequest by providing
a set of wrapper functions for the object.
 The wrapper functions address common infrastructural issues by
providing a unified API, cross-browser compatibility, error handling,
data encoding, and much more.

85 5/19/2012

Cont…
 The four wrapper functions all start with xhr (a short form
of XMLHttpRequest):
 xhrGet() allows you to make an HTTP GET method call to the server.
 xhrPost() allows you to make an HTTP POST method call to the server.
 xhrPut() allows you to make an HTTP PUT method call to the server.
 xhrDelete() allows you to make an HTTP DELETE method call to the
server.

 Dojo also provides a generic xhr() function that takes the name of the
HTTP method that you want to use as an argument and makes the
requested method call.

86 5/19/2012

dojo.xhrGet
 The dojo.xhrGet() function is the cornerstone function of AJAX
development.
 Its purpose is to provide an easy to use and consistent interface to
making asynchronous calls to retrieve data.
 This makes it much simpler to write cross-browser compatible AJAX
style applications.
 This function, in essence, implements making an HTTP 'GET' call.
 Limitations
 dojo.xhrGet (and other functions in the same line: dojo.xhrPost, dojo.xhrDelete,
dojo.xhrPut), are bound by the 'same domain' security policy of the browser.
 This means that they can only establish a connection back to the same server that
served the HTML page.

87 5/19/2012

Ajax XML HttpRequest with Dojo
 A Hello world Dojo Ajax example:

The file “data.txt” has a text statement “Welcome to Dojo Ajax!”.
This Web application just downloads the content of this text file, places
it in the HTML “div” tag “put_here” placeholder, and displays it.
Assume the dojo core package dojo.js library is installed in the dojo
directory in the root directory under webapps in a Web server such as
Apache Tomcat.
If you browse this page, the “Welcome to Dojo Ajax” will be displayed
in the HTML page.

88 5/19/2012

Here is the HTML file with a xhrGet Ajax request.

<html>
<head>
<title>Dojo Ajax</title>
<script type="text/javascript" src='dojo/dojo/dojo.js'></script>
<script>
function welcome() {
dojo.xhrGet( {
url: "data.txt",
// The load function is called on successful response from server
// It inserts the response to the HTML div “put_here” placeholder
load: function(response, ioArgs)
{
dojo.byId("put_here").innerHTML = response;
return response;
},

89 5/19/2012

Contd….
// The error function displays error message if server does not
// respond right
error: function(response, ioArgs)
{
console.error("HTTP status code: ", ioArgs.xhr.status);
return response;
}
});
}
//Invoke the welcome function when dojo starts up
dojo.addOnLoad(welcome);
</script>
</head>
<body>
<div id="put_here" ></div>
</body>
90 5/19/2012
</html>

Example
 One uses Dojo xhrGet function to get data from the server and partially
update the DHTML page without refreshing the whole page, just like all
Ajax requests do. The other uses Dojo xhrPost method to post the
DHTML form data to the server and receives responses back from the
server to partiall update the client page.
 The next example shows a Dojo xhrPost Ajax request in the following
HTML file.
 The request is sent to a JSP called response.jsp, which will respond to the
Ajax xhrPost form request with a provided user name, and say “Hello
<user name>”.

91 5/19/2012

<html>
<head>
<title>Hello User</title>
<script language="javascript"
src="/dojocore/dojo/dojo.js"></script>
<script language="javascript">
dojo.addOnLoad(function() {
var form = dojo.byId("sampleForm"); // save ref to form
dojo.connect(form, "onsubmit", function(e) {
// connect to, and disable the submit of this form
e.preventDefault();
// post the form with all it's defaults
dojo.xhrPost({
92 5/19/2012

form: form,
load: function(data) {
// set the form's HTML to be the response
form.innerHTML = data;
}
});
});
});
</script>
</head>
<body>
<form method="post" id="sampleForm" action="response.jsp">
<h3> Example of using xhrpost</h3><br>
Enter Name: <input type="text" length="20" name="myName"/>
<button type="submit" data-dojo-type="dijit.form.Button"
id="submitButton">Send it!</button>
</form>
<div id='Message'></div>
</body> 5/19/2012
93
</html>

Response.jsp
<%
String name =
request.getParameter("myName");
if (name != null && !name.trim().equals("")) {
out.print("Hello " + name + "!");
} else {
out.print("You didn't enter a name!");
}
%>
94 5/19/2012

Data Source

 A data source is what the name implies, a source that provides data
to something.
 In the case of a data store, a data source is where the data store
obtains its data.
 A data source can be a database, a REST service, or even a JSON file.
For introductory purposes, we will look at the most simple data
source available, a javascript object.

95 5/19/2012

Connecting dijit.Tree
 dojo.require("dojo.data.ItemFileReadStore"); dojo.require("dijit.Tree");
var storeData = { identifier: 'abbr', label: 'name',
items: [
{ abbr:'ec', name:'Ecuador', capital:'Quito' },
{ abbr:'eg', name:'Egypt', capital:'Cairo' },
{ abbr:'sv', name:'El Salvador', capital:'San Salvador' },
{ abbr:'gq', name:'Equatorial Guinea', capital:'Malabo' },
{ abbr:'er', name:'Eritrea', capital:'Asmara' },
{ abbr:'ee', name:'Estonia', capital:'Tallinn' },
{ abbr:'et', name:'Ethiopia', capital:'Addis Ababa' }
]}
<div data-dojo-type="dojo.data.ItemFileReadStore" data-dojo-props="data:storeData"
data-dojo-id="countryStore"></div>
<div data-dojo-type="dijit.tree.ForestStoreModel" data-dojo-id="countryModel"
data-dojo-props="store:countryStore, rootId:'Countries',
rootLabel:'Countries'"></div>
<div data-dojo-type="dijit.Tree" data-dojo-props="model:countryModel"></div>
96 5/19/2012

 In the above example: The data source is the above javascript object
 Each item is a country, and each item has three attributes: name,
abbr, and capital.
 The abbr attribute is an identifier. Each country has a different abbr
for unique look up.
 This is a simple, but powerful, way to represent data in the browser.
It can also be quickly converted to a text format called JavaScript
Object Notation (JSON).
 The JSON format can be stored as files on your server and loaded via
xhr calls.
 dojo.data.ItemFileReadStore allows for the data to be defined in
browser as an object, or from a JSON file of the same format.
 The example shows how a datastore can be used to load the data and
how widgets that are dojo.data aware can make use of it to display it
easily.
97 5/19/2012

dojo.data.ItemFileReadStore
 Dojo core provides an implementation of a read-only
datastore, ItemFileReadStore.
 This store reads the JSON structured contents from an
http endpoint (service or URL), or from an in-memory
JavaScript object, and stores all the items in-memory for
simple and quick access.
 ItemFileReadStore is designed to allow for flexibility in
how it represents item hierarchy, references, and custom
data types.
 It also provides options for which an attribute can act as the
unique identifier, and which attribute can be used as a
general label for an item.
98 http://dojotoolkit.org/reference-guide/1.7/quickstart/data/usingdatastores.html 5/19/2012

Custom Widgets
 Let us create a simple widget that will just say "Hello, World!“.
 First, Within “dojocore/Custom” sub-folder, create a
file CustomWidget.js with the following contents:
 dojo.provide('Custom.CustomWidget');
dojo.require('dijit._Widget');

dojo.declare("Custom.CustomWidget", dijit._Widget,
{
postCreate : function()
{
this.domNode.innerHTML = 'Hello, World!';
}
});

99 5/19/2012

Cont…
 One of the more important functions of the
object dijit._Widget is postCreate.
 We override the method to provide our implementation and that is
to simply set theinnerHTML of the container to the text Hello,
World!.
 Now that we have got the widget, we do not know how and if it
works.
 So, let's just write a simple test page (HTML) to use it. Create a file
Web Pages/custom-widget-test.html with the following contents.

100 5/19/2012

<html>
<head>
<title>Custom Widget Test</title>
<script type="text/javascript" language='javascript'
src="dojocore/dojo/dojo.js" djConfig="isDebug: true,
parseOnLoad: true"></script>
<script type='text/javascript' language='javascript'>
dojo.require('dijit.form.Button');
dojo.require(‘Custom.CustomWidget');
</script>
</head>
<body>
<div id='w1' dojoType=‘Custom.CustomWidget'></div>
</body>
</html>

101 5/19/2012

Customizing the Widget
 The next step is to customize the Hello, World! with a user defined
content.
 Let's say that the default value of the content to be displayed is Hello,
World!. To this effect, update the CustomWidget.js as follows:
dojo.declare(“Custom.CustomWidget", dijit._Widget,
{
text: 'Hello, World!',
postCreate : function() {
this.domNode.innerHTML = this.text;
}
});

 Simultaneously, we update the custom-widget-test.html file to as follows:
 <body>
<div id='w1' text='Hello, Java World!'
dojoType=‘Custom.CustomWidget'></div>
</body>
102 5/19/2012

Templated Widgets
 Dijit sub-framework in Dojo Toolkit provides a support for
templated widgets through the object dijit._Templated.
 Well, we do not inherit this but use as a mixin and
choosedijit._Widget as the parent object.
 _TemplatedMixin implements buildRendering() for you, and all you
have to do is specify a template i.e, an HTML fragment, that specifies
the DOM for the widget.

103 http://livedocs.dojotoolkit.org/quickstart/writingWidgets 5/19/2012

References:
 http://ofps.oreilly.com/titles/9780596516482/index.html
 http://livedocs.dojotoolkit.org/dojo/request/
 http://dojotoolkit.org/documentation/tutorials/1.6/declare/
 http://www.javaworld.com/javaworld/jw-01-2009/jw-01-
introduction-to-dojo-1.html?page=1
 http://dojotoolkit.org/reference-guide/1.7/dojo/data.html#dojo-
data
 http://www.java2s.com/Tutorial/JavaScript/0570__Dojo-
toolkit/Catalog0570__Dojo-toolkit.htm
 http://www.roseindia.net/dojo/index.shtml
 http://www.json.org/

105 5/19/2012

Complete Dojo

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