New Features of ZK 8.5.0

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DocumentationSmall Talks2017OctoberNew Features of ZK 8.5.0
New Features of ZK 8.5.0

Hawk Chen, Engineer, Potix Corporation
October 31, 2017
ZK 8.5.0


In ZK 8, we provided MVVM shadow elements, client-side command binding, and data-handler to allow developers combining the simplicity and security of the server-centric architecture with the beauty and dynamics of the evolving client-side technologies.

The new ZK 8.5 takes the best of ZK 8 and continues to push the innovation envelope. A major improvement on MVVM data binding at the client side enlivened pure HTML content with minimal effort. The new built-in websocket support allows you to handle real-time data in a more efficient way, while the Fragment component made it easy to develop a PWA with ZK.

Highlighted features:

  • WebSocket
  • New default theme and 24 freshly baked themes
  • New component: Fragment
  • New Layout - splitlayout
  • Browser History (HTML5) Management
  • Source Maps for WPD Files

Read more about why ZK 8.5

Watch recorded ZK 8.5 walk-through session

Download and Demo

Highlighted Features

WebSocket Empowers the Communication with a Server

  • Available for ZK:
  • ee.png

WebSocket is a new communication protocol standardized by the IETF as RFC 6455. It provides a full-duplex communication channel over a single TCP connection. Once the WebSocket connection has been established, all subsequent messages are transmitted over the socket rather than new HTTP requests/responses. Therefore, it can lower handshake overhead and reduce a lot of HTTP requests when there are many small updates comparing to AJAX server push. A server can actively send data to a client without a client's request. So it's more trivial than Comet. ZK now supports not only WebSocket-based update engine but also a WebSocket-based server push.

To enable websockets in ZK 8.5 all you need is to add the following <listener> to your zk.xml:


More details

Supported Servers

According to Oracle article, websocket API (JSR 356) is a part of Java EE 7 standard. So all Java EE 7-compliant servers can support the API. You can check a list of compatible servers, Tomcat.

New Default Theme - Iceblue

  • Available for ZK:
  • ce-pe-ee.png

A good, elegant-designed web user interface convinces users that your application is well-built and presents a professional impression. Therefore, in order to keep up with modern web design, we crafted a new flat design theme as ZK 8.5's default theme - Iceblue. With Iceblue your web application will immediately have a modern and refreshing look.


Theme Demo

Tips for Migrating to Iceblue Theme

To start a new project with Iceblue Theme there is nothing to configure. However, if you already have an existing ZK application based on the breeze theme, and you wish to migrate to the new Iceblue theme then you may need to tweak it accordingly. Since Iceblue has a larger font size, padding, and margin, anything specified with a fixed size might break the layout after migration. Please check the followings and adjust as needed:

  • Components have fixed width and height specified
  • Components arranged horizontally might produce a new line.
  • Custom CSS related to size
  • Custom JavaScript code that is related to size

Keep Using The Previous Default Theme - Breeze

For existing ZK-based systems, you can still keep using the previous default theme, Breeze, if you are not ready to migrate to Iceblue. You can easily switch back to Breeze theme. Just get the breeze theme jar via Maven (or download and change the preferred theme name to "breeze" in zk.xml. Please refer to Switching Themes.

Set the preferred theme to breeze in zk.xml:


Maven users have to add a new dependency to pom.xml (using the same version as the zk dependencies)


Lite, Dark, and Mix-matched Modern Themes

  • Available for ZK:
  • ee.png

In addition to Iceblue, there are 23 more freshly baked, colorful modern themes for you to choose from. Theme Demo.


ZK85 Theme Lite.png


ZK85 Theme Dark.png


ZK85 Theme Mix.png

You can even allow each end user set his or her preferred theme in your application with cookies like:

Themes.setTheme(Executions.getCurrent(), "custom");

Please refer to Switching Themes for more details.

New Component with Client Data Binding - Fragment

  • Available for ZK:
  • ee.png

Fragment is a special component that turns a static HTML page into dynamic. It can bind an HTML snippet with data from a ViewModel with ZK data binding syntax. With this powerful component, you can create a custom HTML widget that's not part of standard ZK components, e.g. custom layouts or custom components, and it binds the data from a ViewModel.

For example, you can build a lightweight grid layout:


Please refer to this blog article for details.

Or, build a custom slider:


How it Works

Fragment is a data container and renderer. It synchronizes data between itself and a server according to data binding syntax, and it stores the data from server as JSON objects at the client-side. Inside a Fragment, the specified data binding syntax actually binds the JSON objects, and it renders HTML elements based on the JSON objects. This also reduces the server's tracking nodes for data binding since data is tracked at the client-side.


New Layout - Splitlayout

  • Available for ZK:
  • ee.png

Splitlayout is a flexible and lightweight layout container, which can split its children into 2 divisions with a draggable splitter. The two child components inside Splitlayout are placed either horizontally or vertically according to orientation attribute, and users can easily resize these two viewports by dragging the splitter bar. You can split an area into three or more divisions by putting a Splitlayout into an outer Splitlayout. In addition, you can even close and open a division by clicking the splitter's caret icon.

ZK Demo - Splitlayout

Manipulating Browser History (HTML5)

  • Available for ZK:
  • ce-pe-ee.png

If your users need to bookmark or navigate to a certain state for a zul, you definitely need this feature. This feature allows you to manipulate browser history in Java. You can push and replace history entries and receive an event when users move forward or back in a history.


In the application above, when I click buttons or select a tab, it will push a state to browser history and change the anchor in the URL. And when I press "back" or "forward" button in the browser, it will switch to the previous tab I selected instead of loading the previous page again.

This feature's underlying implementation relies on browser history object's API, e.g. history.pushState(). For details, please refer to Browser History Management.

Provide Source Maps for WPD Files

  • Available for ZK:
  • ce-pe-ee.png

From now on, it's easy to check widgets' javascript source in a browser with a developer tool. In previous versions, ZK merges/compresses javascript code into WPD files, but now you can see separate javascript files for each widget with comments like:


After you enable javascript in zk.xml with the property below:


If your browser supports source map, you can also see separate js files for every ZK widgets, not just WPD files (compressed files). It's very useful when you wish to debug javascript code or customize widgets. You can still debug with uncompressed WPD even a browser doesn't support this.

Notice: This Feature Includes a Big JAR File

In order to generate source map, ZK includes closure-compiler as a dependency. If you package it and its dependencies, it increases about 10MB for a WAR. It's usually unnecessary for your production server, you can exclude it in a pom.xml like:

  • Line 2: For PE users, you exclude it under zkex. For EE users, you exclude it under zkmax.

Other Enhancements

Grid Supports Display by Rows

  • Available for ZK:
  • ce-pe-ee.png

Now you have the flexibility to limit the visible rows of Grid/Tree like Listbox:

Notice that the attribute name is visibleRows for Grid.

<grid visibleRows="5">
<tree rows="3" >

Enhanced Scrolling with Frozen Grid

  • Available for ZK:
  • ee.png

We improved the column scrolling of a Frozen Grid. In the previous version, you can only scroll unfrozen columns one by one. Now you can scroll them smoothly.

More details

Stacked Font Awesome Icons

  • Available for ZK:
  • ce-pe-ee.png

Thanks to contributor szediwy's effort, now ZK supports stacked font awesome icons.

Tbeditor Upgrade

  • Available for ZK:
  • ee.png

We upgraded the component's bundled trumbowyg to 2.3.0 in order to benefit from more plugins and bug fixes.

CKEditor Upgrade

The major change is we upgraded the bundled CKEditor to 4.7.0 to get more features and bug fixes.


  • ZKCK-33: Update ckez source to current version
  • ZKCK-39: Editor upgrade to current latest release CKEditor 4.7.0


  • ZKCK-34: Zkoss CKEditor vulnerable to file browsing
  • ZKCK-40: Memory leak in CKEditor
  • ZKCK-28: quick successive bindings cause exception
  • ZKCK-30: CKeditor prevent some events, causes popups to not close.
  • ZKCK-37: CKEditor maxized content disappear with vflex 1

New Tooltip API

  • Available for ZK:
  • ce-pe-ee.png

This new API gives you more flexibility to add a tooltip or a popup on a component under MVC approach.

public void setTooltipAttributes(Popup popup, String position, String x, String y, Integer delay) 
public void setPopupAttributes(Popup popup, String position, String x, String y, String type)


New Key Support

  • Available for ZK:
  • ce-pe-ee.png

Shift + up key can deselect listitems


If you select multiple items with shift + down, now you can deselect them with shift + up.

KeyEvent supports to detect the command key pressed

ZK now can detect Mac command key pressed. Please refer to Allowed Control Keys for more details.


ZK is made by Java developers for Java developers; continue bringing technology innovations to enterprise Java web development has always been our top priority. ZK 8.5 provides a great balance between the required server-side simplicity, security, and integrity and the client-side usability, look, and feel.
Join us this fall and harvest Javascript from Java roots!

ZK grows with you. Feel free to share with us your feedback or suggestion.


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