Chapter 14. Internationalization and themes

Seam makes it easy to build internationalized applications by providing several built-in components for handling multi-language UI messages.

14.1. Locales

Each user login session has an associated instance of java.util.Locale (available to the application as a component named locale). Under normal circumstances, you won't need to do any special configuration to set the locale. Seam just delegates to JSF to determine the active locale:

  • If there is a locale associated with the HTTP request (the browser locale), and that locale is in the list of supported locales from faces-config.xml, use that locale for the rest of the session.

  • Otherwise, if a default locale was specified in the faces-config.xml, use that locale for the rest of the session.

  • Otherwise, use the default locale of the server.

It is possible to set the locale manually via the Seam configuration properties, and, but we can't think of any good reason to ever do this.

It is, however, useful to allow the user to set the locale manually via the application user interface. Seam provides built-in functionality for overriding the locale determined by the algorithm above. All you have to do is add the following fragment to a form in your JSP or Facelets page:

<h:selectOneMenu value="#{localeSelector.language}">
    <f:selectItem itemLabel="English" itemValue="en"/>
    <f:selectItem itemLabel="Deutsch" itemValue="de"/>
    <f:selectItem itemLabel="Francais" itemValue="fr"/>
<h:commandButton action="#{}" value="#{messages['ChangeLanguage']}"/>

Or, if you want a list of all supported locales from faces-config.xml, just use:

<h:selectOneMenu value="#{localeSelector.localeString}">
    <f:selectItems value="#{localeSelector.supportedLocales}"/>
<h:commandButton action="#{}" value="#{messages['ChangeLanguage']}"/>

When this use selects an item from the drop-down, and clicks the button, the Seam and JSF locales will be overridden for the rest of the session.

14.2. Labels

JSF supports internationalization of user interface labels and descriptive text via the use of <f:loadBundle />. You can use this approach in Seam applications. Alternatively, you can take advantage of the Seam messages component to display templated labels with embedded EL expressions.

14.2.1. Defining labels

Seam provides a java.util.ResourceBundle (available to the application as a org.jboss.seam.core.resourceBundle). You'll need to make your internationalized labels available via this special resource bundle. By default, the resource bundle used by Seam is named messages and so you'll need to define your labels in files named,,, etc. These files usually belong in the WEB-INF/classes directory.

So, in


And in


You can select a different name for the resource bundle by setting the Seam configuration property named org.jboss.seam.core.resourceLoader.bundleNames. You can even specify a list of resource bundle names to be searched (depth first) for messages.


If you want to define a message just for a particular page, you can specify it in a resource bundle with the same name as the JSF view id, with the leading / and trailing file extension removed. So we could put our message in welcome/ if we only needed to display the message on /welcome/hello.jsp.

You can even specify an explicit bundle name in pages.xml:

<page view-id="/welcome/hello.jsp" bundle="HelloMessages"/>

Then we could use messages defined in on /welcome/hello.jsp.

14.2.2. Displaying labels

If you define your labels using the Seam resource bundle, you'll be able to use them without having to type <f:loadBundle ... /> on every page. Instead, you can simply type:

<h:outputText value="#{messages['Hello']}"/>


<h:outputText value="#{messages.Hello}"/>

Even better, the messages themselves may contain EL expressions:

Hello=Hello, #{user.firstName} #{user.lastName}
Hello=G'day, #{user.firstName}

You can even use the messages in your code:

@In private Map<String, String> messages;
@In("#{messages['Hello']}") private String helloMessage;

14.2.3. Faces messages

The facesMessages component is a super-convenient way to display success or failure messages to the user. The functionality we just described also works for faces messages:

public class HelloBean implements Hello {
    @In FacesMessages facesMessages;
    public String sayIt() {

This will display Hello, Gavin King or G'day, Gavin, depending upon the user's locale.

14.3. Timezones

There is also a session-scoped instance of java.util.Timezone, named, and a Seam component for changing the timezone named By default, the timezone is the default timezone of the server. Unfortunately, the JSF specification says that all dates and times should be assumed to be UTC, and displayed as UTC, unless a timezone is explicitly specified using <f:convertDateTime>. This is an extremely inconvenient default behavior.

Seam overrides this behavior, and defaults all dates and times to the Seam timezone. In addition, Seam provides the <s:convertDateTime> tag which always performs conversions in the Seam timezone.

14.4. Themes

Seam applications are also very easily skinnable. The theme API is very similar to the localization API, but of course these two concerns are orthogonal, and some applications support both localization and themes.

First, configure the set of supported themes:

<theme:theme-selector cookie-enabled="true">

Note that the first theme listed is the default theme.

Themes are defined in a properties file with the same name as the theme. For example, the default theme is defined as a set of entries in For example, might define:

css ../screen.css
template /template.xhtml

Usually the entries in a theme resource bundle will be paths to CSS styles or images and names of facelets templates (unlike localization resource bundles which are usually text).

Now we can use these entries in our JSP or facelets pages. For example, to theme the stylesheet in a facelets page:

<link href="#{theme.css}" rel="stylesheet" type="text/css" />

Or, when the page definition resides in a subdirectory:

<link href="#{facesContext.externalContext.requestContextPath}#{theme.css}" 
    rel="stylesheet" type="text/css" />

Most powerfully, facelets lets us theme the template used by a <ui:composition>:

<ui:composition xmlns=""

Just like the locale selector, there is a built-in theme selector to allow the user to freely switch themes:

<h:selectOneMenu value="#{themeSelector.theme}">
    <f:selectItems value="#{themeSelector.themes}"/>
<h:commandButton action="#{}" value="Select Theme"/>

14.5. Persisting locale and theme preferences via cookies

The locale selector, theme selector and timezone selector all support persistence of locale and theme preference to a cookie. Simply set the cookie-enabled property in components.xml:

<theme:theme-selector cookie-enabled="true">

<international:locale-selector cookie-enabled="true"/>