ZK Developer's Reference/UI Composing/ZUML

Overview

There are two ways to compose UI: XML-based approach and pure-Java approach. Here we describe XML-based approach. For pure-Java approach, please refer the next chapter.

The declaration language is called ZK User Interface Markup Language (ZUML). It is based on XML. Each XML element instructs the ZK Loader which component to create. Each XML attribute describes what value to be assigned to the created component. Each XML processing instruction describes how to process the whole page, such as the page title. For example,

<?page title="Super Application"?>
<window title="Super Hello" border="normal">
    <button label="hi" onClick='alert("hi")'/>

where the first line specifies the page title, the second line creates a root component with title and border, and the third line creates a button with label and an event listener.

This chapter is about the general use of ZUML. For a complete reference, please refer to ZUML Reference.

Auto-completion with Schema

Many IDEs, such Eclipse, supports auto-completion if XML schema is specified as follows.

 <window xmlns="http://www.zkoss.org/2005/zul"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://www.zkoss.org/2005/zul http://www.zkoss.org/2005/zul/zul.xsd">

In addition to downloading from http://www.zkoss.org/2005/zul/zul.xsd, you can find zul.xsd under the dist/xsd directory in the ZK binary distribution.

Language

A language (LanguageDefinition) is a collection of component definitions. It is also known as a component set.

For example, Window, Button and Combobox all belong to the same language called xul/html, which is also known as zul.

Component designers are free to designate a component definition to any component set they prefer, as long as there is no name conflict. In additions, it is OK to use components from several languages in the same ZUML page.

Language Identification

When parsing a ZUML document, ZK Loader have to decide the language that a XML element is associated, such that the correct component definition (ComponentDefinition) can be resolved. For example, in the following example, ZK needs to know window belongs to the xul/html language.

<window>

There are two ways to identify a language: filename's extension and XML namespace. Here are an overview of them. For more information please refer to ZUML Reference.

Identify by Filename's Extension

First, when a ZUML file is parsed, the language will be decided based on the extension of the filename or a URI (LanguageDefinition.getByExtension(String)). For example, the extensions associated with xul/html are zul and xul. Thus, if any file whose extension is zul or xul, the default language used to parse it will be assumed to be the xul/html language.

Another example: xhtml is another language (aka., a component set). It is associated with the extensions including zhtml, html, html, and xhtml. Thus, any file whose extension matches one of them will be considered as applying the zhtml language as default.

Notice that the association of filename's extension with a language is about how ZK Loader processes a ZUML page. To really have ZK Loader to process a file, you have to configure WEB-INF/web.xml correctly. For example, if you want to map all XUL files to ZK Loader, you could add the following to WEB-INF/web.xml:

<servlet-mapping>
	<servlet-name>zkLoader</servlet-name>
	<url-pattern>*.xul</url-pattern>
</servlet-mapping>

Identify by XML Namespace

If you map ZK Loader to a filename's extension that is not recognized, you could use XML namespaces to specify the language used to parse it. Each language is associated with a unique XML namespace that you can identify it easily in a ZUML document.

For example, you map ZK Loader to *.foo, then you could specify the xul/html language's namespace, which is http://www.zkoss.org/2005/zul:

<window xmlns="http://www.zkoss.org/2005/zul">
...

where the xmlns attribute declares a XML namespace to associate all element without explicit prefix, such as window in this case.

If you want to use several languages in the same XML document, you could use XML namespaces to distinguish them too. For example, the xhtml language's namespace is http://www.w3.org/1999/xhtml, and we could do as follows.

<window xmlns:h="http://www.w3.org/1999/xhtml">
    <h:table>
        <h:tr>
            <h:td>
                <button/>
            </h:td>
        </h:tr>
    </h:table>
</window>

Notice that table, tr and td are also components though they are very simple -- a simple wrapper of HTML tags. There is a better way to generate HTML tags: the native namespace. For more information please refer to the Native Namespace section.

Identify by XML Namespace with Shortcut

To make it easy to specify a namespace, you could specify a shortcut instead of the full namespace URI. For languages, the shortcut is the last word of the namespace URI. For example, zul for http://www.zkoss.org/2005/zul, and xhtml for http://www.w3.org/1999/xhtml. Thus, we can simply the previous example as follows.

<window xmlns:h="xhtml">
    <h:span>
        <h:tr>
            <h:td>
                <button/>
            </h:td>
        </h:tr>
    </h:table>
</window>

Version History

Last Update : 2010/12/3

Version	Date	Content
5.0.4	August, 2010	The shortcut was introduced to make it easy to specify a standard namespace, such as native, client and zk.
5.0.5	October, 2010	The shortcut was introduced to make it easy to specify a component set, such as zul and zhtml.