Welcome!

Java IoT Authors: Pat Romanski, Elizabeth White, Liz McMillan, Yeshim Deniz, Mehdi Daoudi

Related Topics: Machine Learning , Java IoT

Machine Learning : Article

AjaxWorld Special: Creating AJAX and Rich Internet Components with JSF

AJAX has gained momentum primarily due to the "XMLHttpRequest" browser object which supports asynchronous communication

This article is based on, and contains excerpts from, the book Pro JSF: Building Rich Internet Components by Jonas Jacobi and John Fallows, published by Apress. Book is now available on fine bookstores and Amazon as of February 25, 2006.

JavaServer Faces (JSF) standardizes the server-side component model for Web application development but doesn't standardize the presentation layer at the browser. In a series of articles we are going to look at how JSF can fulfill new presentation requirements without sacrificing application developer productivity building Rich Internet Applications (RIA).

Consumer Requirements
It's always the end user who feels the effect of any chosen technology, especially at the presentation layer. The end-user experience should be top priority for any developer building applications, whether they are Web applications or desktop applications. End users demand feature-rich and highly interactive user interfaces.

Introduction to Rich Internet Technologies
Web application developers today are faced with higher demand for richer functionality using technologies such as HTML, CSS, JavaScript, and DOM. These technologies were not developed with enterprise applications in mind and, with increasing pressure from consumers to provide applications with features not fully described or supported by these technologies, developers are looking for alternative solutions or extensions to these standards.

From a combination of both consumer requirements and developer needs, a new breed of Web technologies has evolved. Often referred to as Rich Internet Technologies, these technologies enhance the traditionally static content provided by Web applications.

In the absence of sufficiently powerful standards, new technologies such as Mozilla's XUL, Microsoft's HTC, Java applets, Flex, and OpenLaszlo have emerged to meet the requirements. Such technologies support application-specific extensions to traditional HTML markup while still leveraging the benefits of deploying an application to a central HTTP server. XMLHTTP has also returned under a newly branded name, AJAX (Asynchronous JavaScript and XML). Applications built with these technologies are often referred to as Rich Internet Applications (RIA).

In this article series we are going to focus on AJAX and XUL to illustrate the potential that JSF brings to the JavaEE developer.

AJAX
AJAX has gained momentum primarily due to the XMLHttpRequest browser object, which supports asynchronous communication with any business services used by the Web application. Popular sites such as Google Mail and Google Suggest use AJAX to deliver RIA.

With the XMLHttpRequest object, developers can now send requests to the Web server to retrieve only the data needed and use JavaScript to process the response.This ability to reduce the amount of data transferred between client and Web server reduces the bandwidth to a minimum and saves processing time on the server since most of the processing is done on the client using JavaScript.

It is important to note that the XMLHttpRequest object, although widely used, could at best be called a "de facto" standard, since most browsers, including Firefox, Inter-net Explorer, Opera, and Safari, support it. It is also worth noting that the XMLHttpRequest object is not exclusive to AJAX; potentially the XMLHttpRequest object can be used by any HTML/XML-based Web technology such as XUL or HTC.

Desktop vs Web
Traditional Web applications are in most cases slower than their counterpart desktop applications. With AJAX we can now send requests to the Web server to retrieve only the data needed and use JavaScript to process the response, which leads to a more responsive Web application.

A typical AJAX application leverages standard HTML/XHTML at the presentation layer and uses JavaScript to dynamically change the DOM. This creates an effect of "richness" in the user interface with no dependency on additional browser plug-ins.

Mozilla XUL
XUL (pronounced zool) was created by the Mozilla organization (Mozilla.org) as an open source project in 1998. With XUL, developers can build rich user interfaces that may be deployed either as "thin client" Web applications, locally on a desktop, or as Internet-enabled "thick client" desktop applications. To fully provide the consumer with a rich user interfaces, XUL needs to execute in the Mozilla Gecko Runtime Environment (GRE). There are many examples of applications using XUL, including the Firefox browser, the Thunderbird e-mail client, and numerous plug-ins to each.

XUL Structure
The base idea behind XUL is to provide a markup for building user interfaces much like HTML, and to leverage technologies such as CSS for look-and-feel and JavaScript for events and behavior. There are even APIs available to access files systems and Web services over the network. As an XML language, XUL can be also be used in combination with other XML languages, such as XHTML and SVG.

XUL Components
XUL comes with a base set of components that are available through the Mozilla GRE, and has the added benefit of not needing to download components to display an application in the browser. You can also design your own components with XUL; these will need to be downloaded on request and cached in the browser.

XUL uses a language called XBL (eXtensible Binding Language) to define new components. XBL is also used to bridge the gap between XUL and HTML, making it easy to attach behavior to traditional HTML markup.

Listing 1 is a sample XUL file that embeds XUL elements and standard, name-spaced HTML elements.

XUL Event Handling
Using XUL event handling is not that different from using HTML event handling. The GRE implementation supports DOM Level 2 (and partially DOM Level 3) and is virtually the same for HTML and XUL, and changes to the state and events are propagated through a range of DOM calls. XUL elements come with predefined event handlers, much like the event handlers provided with the standard HTML elements (see Listing 2).

As in HTML, developers can use JavaScript functions located in external libraries, or embedded in the page.

<script type="text/javascript"src="http://
www.bob.org/js/myscript.js">

There is a large set of built-in XUL components, each with its own set of event handler attributes. For example, the XUL window element delivers events such as load and paint.

Creating Custom XUL Components Using XBL
XBL is an XML language that allows developers to extend XUL by adding "custom" components to the extensive set of existing XUL elements. In XUL, developers can define the look and feel using CSS, and they can define the behavior using XBL.

Developers can look at XUL as the "implementation" that comes with a pre-set of components, or tag libraries that can be used to build a user interface, much like the JSF Reference Implementation. XBL is the language developers use to extend XUL components and enable integration with HTML, in much the same way that Java is used to extend JSF components.

XBL Structure
An XBL file contains a set of bindings, each describing the behavior, properties, and methods of an XUL component.

A quick look at Listing 3 shows the root <bindings> element containing two binding elements. A <bindings> element can contain any number of <binding> elements. The namespace in the <bindings> element defines which syntax will be used, and in Listing 3 it is XBL - xmlns=http://www.mozilla.org/xbl. The file also contains a combination of XUL and HTML elements <xul:text/> and <html:input/>. This is extremely useful for simplifying development by encapsulating several components as a single, reusable component. The xbl:inherits attribute allows the text element to inherit values from the bound element by defining a variable called name and assigns it to the value attribute. If no value is defined when the component is used in a page, the text field's value will default to "Guest".

More Stories By Kaazing Blog

Kaazing is helping define the future of the event-driven enterprise by accelerating the Web for the Internet of Things.

More Stories By John Fallows

John brings to Kaazing his 17 years’ experience in technology development and software design, and is considered a pioneer in the field of rich and highly interactive user interfaces. As CTO he formulates Kaazing Corporation’s vision of enabling mobile users, marketplaces and machines to connect and communicate in real-time, more reliably and at unprecedented scale. He defines the architecture of the Kaazing product suite and oversees its development. Prior to co-founding Kaazing, John served as Architect for Brane Corporation, a startup company based in Redwood City, California. Before joining Brane, he was a Consulting Member of Technical Staff for Server Technologies at Oracle Corporation. During his last five years at Oracle, he focused on designing, developing, and evolving Oracle ADF Faces to fully integrate Ajax technologies. Originally from Northern Ireland, he received his MA in Computer Science from Cambridge University in the United Kingdom and has written several articles for leading IT magazines such as Java Developer’s Journal, AjaxWorld Magazine, and JavaMagazine (DE), and is a popular speaker at international conferences. He is co-author of the bestselling book Pro JSF and Ajax: Building Rich Internet Components (Apress).

Comments (5)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


IoT & Smart Cities Stories
The platform combines the strengths of Singtel's extensive, intelligent network capabilities with Microsoft's cloud expertise to create a unique solution that sets new standards for IoT applications," said Mr Diomedes Kastanis, Head of IoT at Singtel. "Our solution provides speed, transparency and flexibility, paving the way for a more pervasive use of IoT to accelerate enterprises' digitalisation efforts. AI-powered intelligent connectivity over Microsoft Azure will be the fastest connected pat...
There are many examples of disruption in consumer space – Uber disrupting the cab industry, Airbnb disrupting the hospitality industry and so on; but have you wondered who is disrupting support and operations? AISERA helps make businesses and customers successful by offering consumer-like user experience for support and operations. We have built the world’s first AI-driven IT / HR / Cloud / Customer Support and Operations solution.
Codete accelerates their clients growth through technological expertise and experience. Codite team works with organizations to meet the challenges that digitalization presents. Their clients include digital start-ups as well as established enterprises in the IT industry. To stay competitive in a highly innovative IT industry, strong R&D departments and bold spin-off initiatives is a must. Codete Data Science and Software Architects teams help corporate clients to stay up to date with the mod...
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...
Druva is the global leader in Cloud Data Protection and Management, delivering the industry's first data management-as-a-service solution that aggregates data from endpoints, servers and cloud applications and leverages the public cloud to offer a single pane of glass to enable data protection, governance and intelligence-dramatically increasing the availability and visibility of business critical information, while reducing the risk, cost and complexity of managing and protecting it. Druva's...
BMC has unmatched experience in IT management, supporting 92 of the Forbes Global 100, and earning recognition as an ITSM Gartner Magic Quadrant Leader for five years running. Our solutions offer speed, agility, and efficiency to tackle business challenges in the areas of service management, automation, operations, and the mainframe.
The Jevons Paradox suggests that when technological advances increase efficiency of a resource, it results in an overall increase in consumption. Writing on the increased use of coal as a result of technological improvements, 19th-century economist William Stanley Jevons found that these improvements led to the development of new ways to utilize coal. In his session at 19th Cloud Expo, Mark Thiele, Chief Strategy Officer for Apcera, compared the Jevons Paradox to modern-day enterprise IT, examin...
With 10 simultaneous tracks, keynotes, general sessions and targeted breakout classes, @CloudEXPO and DXWorldEXPO are two of the most important technology events of the year. Since its launch over eight years ago, @CloudEXPO and DXWorldEXPO have presented a rock star faculty as well as showcased hundreds of sponsors and exhibitors! In this blog post, we provide 7 tips on how, as part of our world-class faculty, you can deliver one of the most popular sessions at our events. But before reading...
DSR is a supplier of project management, consultancy services and IT solutions that increase effectiveness of a company's operations in the production sector. The company combines in-depth knowledge of international companies with expert knowledge utilising IT tools that support manufacturing and distribution processes. DSR ensures optimization and integration of internal processes which is necessary for companies to grow rapidly. The rapid growth is possible thanks, to specialized services an...
At CloudEXPO Silicon Valley, June 24-26, 2019, Digital Transformation (DX) is a major focus with expanded DevOpsSUMMIT and FinTechEXPO programs within the DXWorldEXPO agenda. Successful transformation requires a laser focus on being data-driven and on using all the tools available that enable transformation if they plan to survive over the long term. A total of 88% of Fortune 500 companies from a generation ago are now out of business. Only 12% still survive. Similar percentages are found throug...