A language (LanguageDefinition) is a collection of component definitions. It is also known as a component set.
Component designers are free to designate a component definition to any component set they prefer, as long as there is no name conflict.
For introduction of languages vs standard namespaces, please refer to ZK Developer's References.
When parsing a ZUML document, ZK Loader has 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 if
window belongs to the xul/html language, so its component definition can be retrieved correctly.
ZK Loader takes the following steps to decide the language an XML element is associated with:
- It assumes a default language for a ZUML document. The default language is decided by the filename's extension (see below).
- If an XML element has no namespace prefix, then
- If an XML element has a prefix, then the XML namespace is used to resolve:
The default language is decided based on the extension of the filename (LanguageDefinition.getByExtension(String)). In addition, a language is associated with one or multiple extensions (defined by the component developer). For example, the extensions associated with the xul/html language are
xul, while the xhtml language (aka., a component set) is associated with the extensions including
Thus, if a file or URI whose extension is
xul, the default language will be assumed to be the
Filename Extension vs URL Mapping
The association of extensions with a language is defined in a language. However, to really have ZK Loader to process a particular 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
<servlet-mapping> <servlet-name>zkLoader</servlet-name> <url-pattern>*.xul</url-pattern> </servlet-mapping>
If the extension of the mapped URL does not match any language, the xul/html language is assumed.
In addition to extension association, a language is also associated with a unique XML namespace. Thus, you can identify the language for a given XML element by the use of XML namespace.
With the XML namespace, you could:
- Map a default language for a unknown extension
- Mix two or more languages in one ZUML document
Map a default language for a unknown extension
For example, you map ZK Loader to
*.foo, which is not associated with any language. Then, you have to specify the XML namespace as shown in the following example:
<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. Furthermore,
http://www.zkoss.org/2005/zul is the unique XML namespace associated with the xul/html namespace.
Mix two or more languages in a ZUML document
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 mix the use 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, when using the xhtml language,
td are also components though they are very simple -- a simple wrapper of HTML tags. However, there is a better way to generate HTML tags: the native namespace. It generates HTML tags directly without maintaining the component. The associated XML namespace of the native namespace is http://www.zkoss.org/2005/zk/native, so we can rewrite the previous example to be more efficient:
<window xmlns:h="http://www.zkoss.org/2005/zk/native"> <h:table> <h:tr> <h:td> <button/> </h:td> </h:tr> </h:table> </window>
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,
xhtml for http://www.w3.org/1999/xhtml. Thus, we can simply the previous example as follows.
<window xmlns:h="xhtml"> <h:table> <h:tr> <h:td> <button/> </h:td> </h:tr> </h:table> </window>
ZK provides three different languages (aka., component sets): xul/xhtml, xhtml and xml. The xul/xhtml and xhtml langauges can be used for any modern browser (Ajax assumed), while the zml language is used for generating XML document (non-Ajax). The developers are free to add their own language.
- Notice that there are so-called Standard Namespaces associated with XML namespaces (for a ZUML document) to provide special functionality (than specify components).
Name: xul/html (aka., zul) File Extensions: zul, xul Namespace: http://www.zkoss.org/2005/zul Namespace shortcut: zul Device: Ajax
Name: xhtml File Extensions: zhtml, xhtml, html, htm Namespace: http://www.w3.org/1999/xhtml Namespace shortcut: xhtml Device: Ajax
XHTML-compliant component sets. It is one-to-one mapping of XHTML tags to ZK components. Since they are components, you can add and remove them dynamically (and control it at the server). For more information please refer to the XHTML Namespace section or ZK Component Reference.
Performance Tip: The XHTML language is designed to allow application to modify the client dynamically (at the server). If you don't need it (it is generally true), you should use the Native namespace instead. For more information, please refer to Performance Tips.
Name: xml File Extensions: xml Namespace: http://www.zkoss.org/2007/xml Namespace shortcut: xml Device: XML Available only ZK EE
XML component sets. It is used to generate (static) XML document. For more information please refer to the XML section.
|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.|