vaadin-framework/documentation/articles/RememberToTheSetTheLocale.asciidoc

---
title: Remember To The Set The Locale
order: 23
layout: page
---

[[remember-to-the-set-the-locale]]
= Remember to the set the locale
The Locale of an application or an individual component dictates the
language and format used for displaying and parsing numbers and dates.
This includes things like names of months, 12 or 24 hour time formats,
the order of days and months in dates, and decimal separators in
numbers.

_Displaying_ values in a locale foreign to the user is bad enough.
Forcing your users to _enter_ values in a foreign locale (such as
decimal separator periods instead of commas, or vice versa) can be
considered a cruel (although sadly not particularly unusual) punishment.

A Vaadin application’s locale, if not explicitly set, defaults to the
locale defined in the request headers sent by the browser , or, if
that’s missing, the locale returned by `java.util.Locale.getDefault()`,
which in turn is the default locale of the Java Virtual Machine, which
depends on the configuration of the environment in which it happens to
be running. Either way, chances are that the end result does not match
what your users expect.

[[per-component]]
Per Component
~~~~~~~~~~~~~

Vaadin components have a *`setLocale()`* method that allows specifying
the locale separately for each component.

[source,java]
....
InlineDateField datePicker = new InlineDateField();
datePicker.setLocale( java.util.Locale.CANADA_FRENCH );
....

[[inheritance]]
Inheritance
^^^^^^^^^^^

A component _inherits its locale_ from its parent. So setting the locale
on a component affects its nested children components by default.
Remember that layouts and even the
https://vaadin.com/api/7.2.5/com/vaadin/ui/UI.html[UI] (Vaadin 7) object
are components too, so setting their locale affects their content.

[[session-default]]
Session Default
~~~~~~~~~~~~~~~

Instead of setting a locale for each individual component, you may set a
Session-wide default. The components inherit that property. You may
continue to override this session-default locale for individual
components, where needed, with a call to `setLocale`.

Setting the default locale changed between Vaadin 6 and 7.

[[in-vaadin-6]]
In Vaadin 6
^^^^^^^^^^^

In Vaadin 6, you set the locale by calling
https://vaadin.com/api/6.8.9/com/vaadin/Application.html#setLocale(java.util.Locale)[`setLocale`]method
on the
https://vaadin.com/api/6.8.9/com/vaadin/Application.html[`Application`]
object. See
https://vaadin.com/book/vaadin6/-/page/advanced.global.html[chapter
12.14 Accessing Session-Global Data] of the Book of Vaadin, Vaadin 6
edition, for important information about accessing the Application
object.

[[in-vaadin-7]]
In Vaadin 7
^^^^^^^^^^^

In Vaadin session, you must go through the current `VaadinSession`
object to call `setLocale`. You may access that object in either of two
ways:

* Through that class’ static method `getCurrent` +
* Jumping from a component object to a UI object to the current
VaadinSession object.

[[bug-workaround]]
Bug & Workaround\\
++++++++++++++++++

Unfortunately, there is a bug (or design issue) in Vaadin 7. See
http://dev.vaadin.com/ticket/12350[ticket 12350]. The problem is that
setting the locale of the VaadinSession does not affect already existing
UI objects. So, while the `init` method of your app's UI is the natural
place to set the session's locale, doing so does not take effect in that
current UI until after a page refresh.

The *workaround* is to explicitly set the current UI object's locale, in
addition to setting the VaadinSession object's locale. The first affects
the current UI, while the second affects any future UI objects that may
be instantiated in your app.

This ( if in a UI object's "init" method)…

[source,java]
....
Locale locale = Locale.CANADA_FRENCH;
this.setLocale( locale ); // Call to affect this current UI. Workaround for bug: http://dev.vaadin.com/ticket/12350
this.getSession().setLocale( locale ); // Affects only future UI instances, not current one because of bug. See workaround in line above.
// VaadinSession.getCurrent().setLocale( locale ); // Alternative to "this.getSession".
....

…or this ( if not in a UI object, add "getUI()" )…

[source,java]
....
Locale locale = Locale.CANADA_FRENCH;
this.getUI().setLocale( locale ); // Call to affect this current UI. Workaround for bug: http://dev.vaadin.com/ticket/12350
this.getUI().getSession().setLocale( locale ); // Affects only future UI instances, not current one because of bug. See workaround in line above.
// VaadinSession.getCurrent().setLocale( locale ); // Alternative to "this.getSession".
....

[[example-app]]
Example App
^^^^^^^^^^^

Here is source code for a complete Vaadin 7 example app.

[source,java]
....
package com.example.vaadinexperiment;

import com.vaadin.annotations.Theme;
import com.vaadin.annotations.VaadinServletConfiguration;
import com.vaadin.server.VaadinRequest;
import com.vaadin.server.VaadinServlet;
import com.vaadin.server.VaadinSession;
import com.vaadin.ui.InlineDateField;
import com.vaadin.ui.UI;
import com.vaadin.ui.VerticalLayout;
import java.util.Locale;
import javax.servlet.annotation.WebServlet;

@Theme ( "mytheme" )
@SuppressWarnings ( "serial" )
public class MyVaadinUI extends UI
{

    @WebServlet ( value = "/*" , asyncSupported = true )
    @VaadinServletConfiguration ( productionMode = false , ui = MyVaadinUI.class , widgetset = "com.example.vaadinexperiment.AppWidgetSet" )
    public static class Servlet extends VaadinServlet
    {
    }

    @Override
    protected void init ( VaadinRequest request )
    {
        final VerticalLayout layout = new VerticalLayout();
        layout.setMargin( true );
        layout.setSpacing( true );
        setContent( layout );

        Locale locale = Locale.CANADA_FRENCH;
        this.setLocale( locale ); // Call to affect this current UI. Workaround for bug: http://dev.vaadin.com/ticket/12350
        this.getSession().setLocale( locale ); // Affects only future UI instances, not current one because of bug. See workaround in line above.
        // VaadinSession.getCurrent().setLocale( locale ); // Alternative to "this.getSession".

        InlineDateField datePicker = new InlineDateField();
        datePicker.setCaption( "This component’s locale → defaults to parent’s, → which defaults to VaadinSession’s, → which defaults to JVM" );
        layout.addComponent( datePicker );

        InlineDateField datePickerFinnish = new InlineDateField();
        datePickerFinnish.setCaption( "This component’s default locale is overridden for Finnish" );
        datePickerFinnish.setLocale( new Locale( "fi" , "FI" ) );
        layout.addComponent( datePickerFinnish );
    }

}
....

image:http://i.imgur.com/w9CViCR.png[Calendar]

'''''

Information here drawn from
http://stackoverflow.com/q/16331112/642706[this StackOverflow.com
question].