Fork me on GitHub
<< back to Core Developers Guide Edit on GitHub

Localization

Overview

The framework supports internationalization (i18n) in the following places:

  1. the UI Tags
  2. Messages and Errors from the ValidationAware
  3. Within action classes that extend ActionSupport through the getText() method

Resource Bundle Search Order

Resource bundles are searched in the following order:

  1. ActionClass.properties
  2. Interface.properties (every interface and sub-interface)
  3. BaseClass.properties (all the way to Object.properties)
  4. ModelDriven’s model (if implements ModelDriven), for the model object repeat from 1
  5. package.properties (of the directory where class is located and every parent directory all the way to the root directory)
  6. search up the i18n message key hierarchy itself
  7. global resource properties

This is how it is implemented in a default implementation of the LocalizedTextProvider interface. You can provide your own implementation using TextProvider and TextProviderFactory interfaces.

To clarify #5, while traversing the package hierarchy, Struts 2 will look for a file package.properties:

com/
    acme/
         package.properties
         actions/
                 package.properties
                 FooAction.java
                 FooAction.properties

If FooAction.properties does not exist, com/acme/action/package.properties will be searched for, if not found com/acme/package.properties, if not found com/package.properties, etc.

Default action’s class

If you configure action as follow

<action name="index">
   <result>/index.jsp</result>
</action>

it will use a default class defined with default-class-ref in struts-default.xml which is com.opensymphony.xwork2.ActionSupport. It means you have two options here to get I18N working in that case:

Examples

There are several ways to access the message resources, including getText, the text tag, and the i18n tag.

Using getText from a Tag

To display i18n text, use a call to getText in the property tag, or any other tag, such as the UI tags. (The getText technique is especially useful for labels of UI tags.)

<s:property value="getText('some.key')" />

The default implementation of TextProvider which is used in ActionSupport perform evaluation of value read from bundle base on the provided key, see [Localizing Output] for an example.

Using the text tag

The text tag retrieves a message from the default resource bundle.

<s:text name="some.key" />

<s:text name="some.invalid.key">
    The Default Message That Will Be Displayed
</s:text>

Using the I18n tag

The i18n tag pushes an arbitrary resource bundle on to the value stack. Other tags within the scope of the i18n tag can display messages from that resource bundle.

<s:i18n name="some.package.bundle"></s:i18n>
  <s:text name="some.key" />
</s:i18n>

Internationalizing SiteMesh decorators is possible, but there are quirks. See SiteMesh Plugin
for more.

Using the Key attribute of UI Tags

The key attribute of most UI tags can be used to retrieve a message from a resource bundle:

<s:textfield key="some.key" name="textfieldName"/>

I18n Interceptor

Essentially, the i18n Interceptor pushes a locale into the ActionContext map upon every request. The framework components that support localization all utilize the ActionContext locale. See I18n Interceptor f or details.

Global Resources (struts.custom.i18n.resources) in struts.properties

A global resource bundle could be specified programmatically, as well as the locale.

Formatting Dates and Numbers

See Formatting Dates and Numbers for more details and examples.

Comparison with Struts 1

Struts 1 users should be familiar with the application.properties resource bundle, where you can put all the messages in the application that are going to be translated. Struts 2, though, splits the resource bundles per action or model class, and you may end up with duplicated messages in those resource bundles. A quick fix for that is to create a file called ActionSupport.properties in com/opensymphony/xwork2 and put it on your classpath. This will only work well if all your actions subclass XWork2’s ActionSupport.

Using only global bundles

If you don’t need to use the package-scan-functionality and only base on the global bundles (those provided by the framework and via struts.custom.i18n.resources) you can use existing GlobalLocalizedTextProvider implementation. To use this please define the following option in your struts.xml:

<constant name="struts.localizedTextProvider" value="global-only" />

Custom TextProvider and TextProviderFactory

If you want use a different logic to search for localized messages, or you want to use a database or just want to search default bundles, you must implement both those interfaces (or subclass the existing implementations). You can check a small example app how to use both. Please remember that the TextProvider interface is implemented by the ActionSupport class, that’s why an extra layer - TextProviderFactory - is needed.