Localization in GWT UiBinder howto

In GWT the localization process is more complex using the UiBinder declarative layout than the Java layout and the official documentation is lacking. In this post I will shortly describe the steps to follow to localize your UiBinder views.
First of all you have to add the local properties to your GWT XML module file:


<inherits name="com.google.gwt.i18n.I18N"/>
<extend-property name="locale" values="en"/>
<extend-property name="locale" values="it"/>


In this example I am considering English and Italian as possible languages. Then you have to add the locale namespaces to any of the *.ui.xml file of your project:


<ui:UiBinder xmlns:ui="urn:ui:com.google.gwt.uibinder"
xmlns:g="urn:import:com.google.gwt.user.client.ui" 
ui:generateFormat="com.google.gwt.i18n.rebind.format.PropertiesFormat"
       ui:generateKeys="com.google.gwt.i18n.rebind.keygen.MD5KeyGenerator"
       ui:generateLocales="default">


Start to add to the XML layout the messages to be localized. Example:


<g:Label horizontalAlignment="ALIGN_CENTER" styleName="titleH2Style">
<ui:msg description="registrationTitle">Registration</ui:msg>  
</g:Label>


Now you need to set Eclipse to generate the resource bundle files. Select the project and click on the GWT Compile Project... button:

The GWT compiler wizard will appear. Click on the Advanced button and then add the following additional compiler argument:
-extra <message_folder>
Example:

Compile the project clicking on the Compile button. At the end of the compilation refresh the project and you will find a generated resource bundle file for each ui.xml layout containing messages to be localized. The generated files have the following naming convention:

<view_full_package_name><view_name><view_name>UiBinderImplGenMessages.properties

Example:

com.myproject.views.RegistrationRegistrationUiBinderImplGenMessages.properties

Inside them you will find the messages in the following format:


# Description: registrationTitle
0F98B7F230F3C91292F0DE4C99E263F2=Registration


Copy these files in the packages containing the corresponding *.ui.xml files and then remove the full package name prefix. Finally duplicate them for each language you need and add the languages suffix to the file names. In our example we will have:

RegistrationRegistrationUiBinderImplGenMessages_en.properties
RegistrationRegistrationUiBinderImplGenMessages_it.properties

Translate the messages and then compile again and start your application to check that everything was fine.
That's all.