Change Form Locale of Vaadin UI on the fly

VaadinUtils.java

/* VaadinUtils.java
 *
 * Created: 2014-03-20 (Year-Month-Day)
 * Character encoding: UTF-8
 *
 ****************************************** LICENSE *******************************************
 *
 * Copyright (c) 2014 XIAM Solutions B.V. (http://www.xiam.nl)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package eu.infomas.vaadin;

import java.lang.reflect.Method;
import java.util.Enumeration;
import java.util.Locale;
import java.util.ResourceBundle;
import java.util.SortedSet;
import java.util.TreeSet;

import com.vaadin.ui.Component;
import com.vaadin.ui.HasComponents;
import com.vaadin.ui.UI;

import eu.infomas.logging.Logger;
import eu.infomas.logging.LoggerFactory;

/**
 * {@code VaadinUtils} offers some utility functions for the 
 * <a href="https://vaadin.com">Vaadin UI Framework</a>.
 *
 * @author <a href="mailto:rmuller@xiam.nl">Ronald K. Muller</a>
 * @since INFOMAS NG 3.0
 */
public final class VaadinUtils {

    private static final Logger LOG = LoggerFactory.getLogger();
    
    // Utility class
    private VaadinUtils() {
    } 
   
    /**
     * Change all {@code Locale} dependant properties of the {@code com.vaadin.ui.Component}s 
     * within of the given component container (typically an {@link UI} or other top level 
     * layout component). 
     * If the specified {@code Locale} is the same as the current {@code Locale} of the 
     * component container, this method does nothing.
     * A property is considered {@code Locale} dependant if there exists a key for this
     * property in the given {@code ResourceBundle}. The key must have the format 
     * "componentId.propertyName", i.e. "user.caption".
     * <p>
     * To use this method, do something like:
     * <pre>
     * public class MyUI extends UI {
     * 
     *     {@literal @}Override
     *     public void setLocale(Locale locale) {
     *         VaadinUtils.updateLocale(this, locale, 
     *             ResourceBundle.getBundle("i18n/Login", locale));
     *         super.setLocale(locale);
     *     }
     * 
     *     {@literal @}Override
     *     public void init(final VaadinRequest request) {
     *         // ... usual code
     *         // somewhere in the UI the user can change the "Form Locale". This code must 
     *         // call myUI#setLocale(newLocale);
     *     }
     * 
     *     // ...
     * 
     * }
     * </pre>
     * 
     * @param ui The component container for which the {@code Locale} dependent component 
     * properties must be changed, never {@code null}
     * @param locale The new {@code Locale}, never {@code null}
     * @param rb The {@code ResourceBundle} for the specified {@code Locale}, 
     * never {@code null} 
     */
    public static void updateLocale(final HasComponents ui, final Locale locale, 
        final ResourceBundle rb) {

        // locale may not be null, howvever the current UI Locale may be null!
        if (locale.equals(ui.getLocale())) {
            return;
        }
        final long time = System.currentTimeMillis();
        final SortedSet<String> ss = new TreeSet<>();
        for (Enumeration<String> e = rb.getKeys(); e.hasMoreElements(); ) {
            ss.add(e.nextElement());
        }
        walkComponentTree(ui, new Consumer<Component>() {

            @Override
            public void accept(Component c) {
                final String id = c.getId();
                if (id == null) {
                    return;
                }
                final Class<?> type = c.getClass();
                final int prefixLen = id.length() + 1;
                // char '/' is the char right after '.' in Unicode
                for (String key : ss.subSet(id.concat("."), id.concat("/"))) {
                    if (rb.containsKey(key)) {
                        // update value!
                        final String mname = keyToMethodName(key, prefixLen);
                        try {
                            final Method m = type.getMethod(mname, String.class);
                            final String value = rb.getString(key);
                            LOG.info("%s(%s) [key=%s]", mname, value, key);
                            m.invoke(c, value);
                        } catch (Exception ex) {
                            LOG.error(ex);
                        }
                    }
                }
            }

        });
        LOG.info("Locale updated: %s -> %s in %d ms.", 
            ui.getLocale(), locale, System.currentTimeMillis() - time);
    }
    
    // private

    // if switching to Java 8, remove this and replace by java.util.funtion.Consumer
    // (and make to code more functional)
    interface Consumer<T> {
        
        void accept(T t);
        
    }

    // recursively walk the Component true
    private static void walkComponentTree(Component c, Consumer<Component> visitor) {
        visitor.accept(c);
        if (c instanceof HasComponents) {
            for (Component child : ((HasComponents)c)) {
                walkComponentTree(child, visitor);
            }
        }
    }    
        
    // keyToMethodName("user.caption", 5) -> "setCaption"
    private static String keyToMethodName(final String key, final int prefixLen) {
        final int n = key.length() - prefixLen;
        final char[] buffer = new char[n + 3];
        "set".getChars(0, 3, buffer, 0);
        key.getChars(prefixLen, prefixLen + n, buffer, 3);
        buffer[3] = Character.toUpperCase(buffer[3]);
        return new String(buffer);
    }

}

This looks interesting but is not working for me. While debugging all components return null when using on line 108 so nothing is actually translated.

I think I found the issue after reading the comments. I'll adjust to my case. Thanks for the code!

See my revision to this code here.

Basically made the following changes:

• Works with Components implementing the Property interface (i.e. Label).
• Works with any component that has an id matching a key in the provided resource bundle. No special formatting needed.
• Works with components with complex captions/values. For example a label with multiple keys.