Client-side UI Composing"

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=Overview=
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Though optional, you could have the total control of the client's functionality without the assistance of server-side coding. Generally, you don't need to do it. You don't even need to know how ZK Client Engine and client-side widgets communicate with the server. Their states can be synchronized automatically with ZK. However, you can still control this type of synchronization if you want. It is the so-called Server-client fusion.
  
[[File:ZKComDevEss_widget_component_application.png]]
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A good rule of thumb is that you should handle events and manipulate UI mostly, if not all, on the server, since it is more productive. Then, you could improve the responsiveness and visual effects, and/or reduce server loading by handling them at the client, when it is appropriate. Notice that JavaScript is readable by any user, so be careful not to expose sensitive data or business logic when migrating some code from server to client.  
  
A UI object visible to a user at the client is hosted by a JavaScript object<ref>It actually depends on the device. For Ajax, it is a JavaScript object. For Android devices, it is a Java object.</ref> called a widget (<javadoc directory="jsdoc">zk.Widget</javadoc>). On the other hand, a component is a Java object (<javadoc>org.zkoss.zk.ui.Component</javadoc>) representing the UI object at the server that an application manipulates directly. Once a component is attached to a page, a widget is created at client automatically. Furthermore, any state change of the component at the server will be updated to the widget at the client.
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* About client-side UI composing, please refer to [[ZK Client-side Reference/General Control/UI Composing|ZK Client-side Reference: UI Composing]].
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* About customizing client-side widget's behavior, please refer to [[ZK Client-side Reference/General Control/Widget Customization|ZK Client-side Reference: Widget Customization]].
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* About client-side event handling, please refer to [[ZK Client-side Reference/General Control/Event Listening|ZK Client-side Reference: Event Listening]]
  
Generally, you need not to know the existence of widgets. Ajax requests and the state synchronization are handled automatically by ZK and the components automatically. However, you are allowed to instantiate or alert any client-side widgets directly at the client (in JavaScript). It is the so-called Server+client fusion.
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=Version History=
 
 
The rule of thumb is to compose and manipulate UI at the server first since it is easier. Then, you could reduce the load of the server by composing some UI at the client when it is appropriate. Notice that JavaScript is readable by any user, so be careful not to expose sensitive data or business logic when migrating some code from server to client.
 
 
 
Here we describe how to compose UI in JavaScript at the client. For client-side event handling, please refer to the [[ZK Developer's Reference/Event Handling/Client-side Event Listening|Client-side Event Handling]] section. For XML-based UI composing at the client, please refer to the [[ZK Developer's Reference/UI Composing/iZUML|iZUML]] section.
 
 
 
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=Modify Widget's State at Client=
 
 
 
While the states of a widget is maintained automatically if you update the corresponding component at the server, you could modify the widget state directly at the server. The modification is straightforward: call the correct method with the arguments you want. Notice that it is JavaScript for Ajax browsers.
 
 
 
<source lang="JavaScript">
 
var foo = zk.Widget.$('foo');
 
foo.setValue("What's Up?");
 
</source>
 
 
 
For a complete API available to the client-side fusion, please refer to http://www.zkoss.org/javadoc/latest/jsdoc/ JavaScript API].
 
 
 
==Fusion with Server-side ZUML and Java==
 
It is suggested that the client-side UI composing is better designed to minimize the network round-trip, provide effects and other enhancement, while the most, if not all, of the application is better to be done at the server. Thus, here we only discuss this kind of addon, aka., fusion. For pure-client approach, please refer to [[Small Talks/2009/July/ZK 5.0 and Client-centric Approach|Small Talk: ZK 5.0 and Client-centric Approach]].
 
 
 
Depending on your requirement, there are typically two situations we could ''fuse'' the client-side code:
 
 
 
#Register a client-side event listener.
 
#Override widget's default behavior
 
 
 
For example, suppose we want to open the drop down when a commbox gains the focus, then we register a client-side event listener for the onFocus event as follows.
 
 
 
<source lang="xml">
 
<div>
 
  <combobox xmlns:w="client" w:onFocus="this.open()"/>
 
</div>
 
</source>
 
 
 
As shown, we have to use the [[ZUML Reference/ZUML/Namespaces/Native|native namespace]] to indicate the onFocus attribute is for the client-side event listener. It is done by apply [http://www.w3schools.com/xml/xml_namespaces.asp XML namespace]:
 
 
 
*Add the <code>xmlns:w="client"</code> attribute
 
*Prefix <code>w:</code> before onFocus
 
  
For more information about the client-side event listener, please refer to the [[ZK Developer's Reference/Event Handling/Client-side Event Listening|Client-side Event Listening]] section.
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The other typical situation to fuse the client-side code is to override the default behavior of a widget. We will discuss it later.
 
 
 
==Identify Widget at Client==
 
 
 
=Instantiate Widget at Client=
 
 
 
A widget has to be create to make a component visible at the client (once it has been attached to a page). However, you could instantiate a widget at client, without the corresponding component at the server. To extreme extent, you could create all widgets at client (of course, it is costly and less secure).
 
 
 
=Override Widget's Default Behavior=
 
 
 
=Version History=
 
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Revision as of 07:37, 8 July 2022


Client-side UI Composing


Though optional, you could have the total control of the client's functionality without the assistance of server-side coding. Generally, you don't need to do it. You don't even need to know how ZK Client Engine and client-side widgets communicate with the server. Their states can be synchronized automatically with ZK. However, you can still control this type of synchronization if you want. It is the so-called Server-client fusion.

A good rule of thumb is that you should handle events and manipulate UI mostly, if not all, on the server, since it is more productive. Then, you could improve the responsiveness and visual effects, and/or reduce server loading by handling them at the client, when it is appropriate. Notice that JavaScript is readable by any user, so be careful not to expose sensitive data or business logic when migrating some code from server to client.

Version History

Version Date Content
     



Last Update : 2022/07/08

Copyright © Potix Corporation. This article is licensed under GNU Free Documentation License.