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The user can switch to a registered theme by setting a cookie or a library property. Please ensure your application contains the corresponding theme jar. (The default theme doesn't require a separate jar file)

Standard theme resolution checks the theme settings in the following order.

  1. Cookies
  2. Library property
  3. Theme priority

Apply a Theme for the Whole Application

This will apply to the whole application as a default theme.


    <!--<value>deepsea</value>--> <!-- no whitespace in theme names -->

Dynamically switching themes using Cookies

To provide different themes for different end users (sessions), you can use cookies since it's stored in a browser.

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

Internally, CookieThemeResolver provides this functionality.

Dynamically Switching Themes Using Library Property

Library property is used to apply a preferred theme when the current theme setting could not be obtained from Cookies. Notice that the property change affects the whole application (all end users).


Library.setProperty("org.zkoss.theme.preferred", "custom");

Theme Priority

If the previous two options do not yield any result, the theme with the highest priority would be applied. Theme priority is usually assigned when registering a theme but could also be changed dynamically.

Please refer to Themes for its family of register() methods.

Customize the Theme Resolution Process

Web developers could also add other ways for setting the current theme by writing a custom ThemeResolver'.

If you would like to communicate theme name via session instead, you would create a class like the following:

package foo;

public class SessionThemeResolver implements ThemeResolver {
    public String getTheme(HttpServletRequest request) {
        Session sess = request.getSession();
        if (sess != null) {
            return sess.getAttribute("mytheme");

    public void setTheme(HttpServletRequest request, HttpServletResponse response, String themeName) {
        Session sess = request.getSession();
        if (sess != null) {
            sess.setAttribute("mytheme", themeName);

and configure the custom ThemeResolver in WEB-INF/zk.xml.


To access the current theme resolver, please refer to ThemeFns.getThemeResolver() and ThemeFns.setThemeResolver(ThemeRegistry).