Dr. Dobb's Journal - February 2008 - (Page 62)

d02seku_p4ma 12/10/07 9:10 AM Page 62 State of the Art THE ZK FRAMEWORK However, directly defining the style for each control is not the best practice. As with HTML, you can define sets of styles for ZUL documents that can be used by passing identifiers (see Listing Five, also online). Multiple Document Interface Displaying child windows is an important technique for constructing complicated UIs in rich client applications. For example, the process allows the separation of some controls into wizards, which help to fill out a form. Unfortunately, such techniques are unavailable in classic web applications. ZK supports the concept by allowing for one page to consist of many nested windows, which also can be modal. Each of these windows is placed in a separated CSS layer and, with help of a mouse, users can move, resize, or close them. For each window, a server creates its own event-handling thread. To use this technique in ZUL, you apply the tag declared with parameter mode set to overlapped or modal; see Listing Six (online). Visualizing Tabular Data Creating tables in ZK is simplified using the forEach attribute, which can be applied to any ZUL component. It accepts values of type java.util.Collection or arrays. Using this attribute causes a tag that is owner of the attribute to be displayed multiple times. Listing Seven (available online) is an example of this technique. Listing Seven includes a script that prepares data for tables (the default scripting language in ZK is BeanShell, which mimics Java; you can also use Groovy or Ruby). It is executed each time ZK loads the page. Then, Listing Seven defines a table and its headers (tags and ) followed by a definition of table rows. Every control that has a tag as its parent is interpreted as a definition of one table cell. The forEach attribute causes multiplication of the row definition for every element of array tabularData. The variable each takes subsequent values from the array backing the loop. This variable is defined in zscript, but it also accessible from EL expressions. Listing One ZKdemo index.html index.zul ZK loader for evaluating ZK pages zkLoader org.zkoss.zk.ui.http.DHtmlLayoutServlet update-uri /zkau 1 The asynchronous update engine for ZK auEngine org.zkoss.zk.au.http.DHtmlUpdateServlet zkLoader *.zul zkLoader *.zhtml auEngine /zkau/* Used to cleanup when a session is destroyed ZK Session Cleaner org.zkoss.zk.ui.http.HttpSessionListener Tables With Dynamic Content Now assume that you want to display a list of objects with mutable content; for instance, a list controlled by user-defined filtering. In Swing applications, you define a model and a view. Then you modify only the model, which automatically notifies the view about its changes, allowing the view to update displayed data. This is a benefit of the MVC pattern, implemented by JTable. In ZK, you proceed in a similar way, and a table is updated without reloading the whole page—only the necessary fragment of HTML code is changed (see Listing Eight, available online). Tables With Nested Controls You often need to add more interactivity to the UI table cells than just plain labels provide. For example, you might want to edit data directly in a table, or add special columns with edit or delete buttons. If you assume that a table will have invariable data, you can embed controls as in Listing Nine (available online). Listing Two 62 Dr. Dobb’s Journal l www.ddj.com l February 2008 http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd 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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