Dr. Dobb's Journal - February 2008 - (Page 61)

d02seku_p4ma 12/12/07 9:40 AM Page 61 Discover a New World in Programming Figure 1: The ZK Framework architecture. engine notifies the server about the event. ZK receives the event on the server side, and actualizes a state of components representing page elements. Changes made by users on the form are introduced to the component tree reflecting form elements. An appropriate event handler is then called. The method can read updated data from the form, perform some operations on the database, then decide about modification of displayed data or page structure, displaying validation messages or some question directed to the user. ZK passes these orders back to the JavaScript engine working on the browser side, which executes appropriate modifications of HTML DOM. Defining of Forms The most convenient way of describing web pages in the ZK environment is via the ZUL language—a subset of XML for describing web UIs. ZUL document tags correspond to graphic controls on forms and are nested in the same way as the controls are embedded on the page. This is an idea borrowed from XUL and developed by Mozilla. A similar concept is XAML implemented in the most recent version of Windows. Compared to traditional methods of creating UIs via specialized APIs (as in GWT), such a declarative solution results in shorter, more lucid code, reducing development time and making maintenance easier. Listing Two is a ZUL document, and Figure 2 is a page rendered on its basics (with some enhancements). This page consists of a window that embodies page content, a label for displaying messages, and a button triggering server-side action. On a display request, ZK creates a page initiator object of the type HelloWorldInit and window controller HelloWorldCtrler. The identifier helloWindow is a reference to the controller object and allows for calling its methods inside scriptlets placed on ZUL pages. Listing Three (available online) is the initiator of this page. Its task is to set up the helloMsg variable in the page context before rendering. The variable is accessible for EL (“Expression Language”), the same language as in standard JSP. The HelloWorldCtrler class (Listing Four, online) enhances the component definition org.zkoss.zul.Window. Its showTime method invokes getFellow from the base class to find a Label component. A change of state of this component is automatically reflected on the client side, without the need to reload the whole page and without web developers writing a single line of JavaScript code. Looking for a career with an innovative company where you can use your programming skills to make a difference in the world? Join ESRI and design and develop the next generation of our world-leading geographic information system (GIS) mapping software. We are seeking software developers with solid core programming skills and a passion for inventing new technology. We have opportunities to work on everything from database and Web development to graphics, 2D–3D rendering, and core server technology. Our developers work with the latest technologies including Java, .NET, and Flash/Flex. At ESRI you’ll have exceptional benefits, opportunities for growth, and the satisfaction of developing software that is making a difference. Join us and be a part of changing the world. Learn more about ESRI and apply online at www.esri.com/ddj. Beautifying the Page You can modify the appearance of ZUL components using Cascading Style Sheets (CSS), in a way similar to HTML documents. For instance, you can make the font of the message thicker with: Copyright © 2007 ESRI. All rights reserved. ESRI, the ESRI globe logo, and www.esri.com, are trademarks, registered trademarks, or service marks of ESRI in the United States, the European Community, or certain other jurisdictions. Other companies and products mentioned herein may be trademarks or registered trademarks of their respective trademark owners. ESRI is an Equal Opportunity Employer. February 2008 l www.ddj.com l Dr. Dobb’s Journal 61 http://www.esri.com/ddj http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - February 2008

Dr. Dobb's Journal - February 2008 Contents Hmmmm Alia Vox Developer Diaries Developer’s Notebook South American Software Development Conversations Inside Visual Studio 2008 BibPort: Creating Bibliographic References Continuous LINQ The ZK Framework Static Testing C++ Code The Agile Edge Effective Concurrency Swaine’s Flames

Dr. Dobb's Journal - February 2008

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