Summary and Further Readings

This article is out of date, please refer to http://books.zkoss.org/zkessentials-book/master/ for more up to date information.

We glimpsed into the fundamental principles behind how ZK works and we employed some of the essential features of ZK to build a sample shopping cart applications in this book. Let's recap on these elements in ZK:

Components

• • Components are UI elements that an application developer piece together to build the application UI. Think LEGO, consult Component Reference guide on what children components a particular component can have.
  • Components can be declared in ZUML (ZK User Interface Markup Language, in XML syntax), or alternatively, in Java.
  • Components (POJO) run on JVM at the server, and they have their counter parts (widgets - JS objects) at the client.
  • User activities on widgets are reflected to the components at the server; component updates are reflected back to the widgets at client.
  • A Page is a "stage" where components come on and off it to play their parts and fulfill their roles.
  • Components are conceptually grouped in ID Spaces; we can call the Component.getFellow() method on one component to get another component as long as they are in the same ID Space.
  • By default, components declared in Window form an ID Space (including Window itself) with Window being the ID Space Ownder.
  • By default, a Page is an ID Space Owner; any component can become the ID Space Owner by implementing IdSpace

Events

• • User activities (eg. onClick) and system notifications (eg. server push) are abstracted to event objects.
  • Register event listeners on components so event objects can be created and forwarded.
  • By default, all events are send to the server for processing.
  • With ZK's Server+client Fusion architecture, events could also be handled at the client directly.
  • Event handling code can be declared as a component attribute in ZUL.
  • Events can be forwarded to a controller class for handling.
  • Event listeners can be added dynamically in Java.