org.eclipse.jgit.nls.NLS.java Source code

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Here is the source code for org.eclipse.jgit.nls.NLS.java

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/*
 * Copyright (C) 2010, Sasa Zivkov <sasa.zivkov@sap.com>
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.eclipse.jgit.nls;

import java.util.Locale;
import java.util.concurrent.ConcurrentHashMap;

import org.eclipse.jgit.errors.TranslationBundleLoadingException;
import org.eclipse.jgit.errors.TranslationStringMissingException;

/**
 * The purpose of this class is to provide NLS (National Language Support)
 * configurable per thread.
 *
 * <p>
 * The {@link #setLocale(Locale)} method is used to configure locale for the
 * calling thread. The locale setting is thread inheritable. This means that a
 * child thread will have the same locale setting as its creator thread until it
 * changes it explicitly.
 *
 * <p>
 * Example of usage:
 *
 * <pre>
 * NLS.setLocale(Locale.GERMAN);
 * TransportText t = NLS.getBundleFor(TransportText.class);
 * </pre>
 */
public class NLS {
    /**
     * The root locale constant. It is defined here because the Locale.ROOT is
     * not defined in Java 5
     */
    public static final Locale ROOT_LOCALE = new Locale("", "", ""); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$

    private static final InheritableThreadLocal<NLS> local = new InheritableThreadLocal<>();

    /**
     * Sets the locale for the calling thread.
     * <p>
     * The {@link #getBundleFor(Class)} method will honor this setting if it
     * is supported by the provided resource bundle property files. Otherwise,
     * it will use a fall back locale as described in the
     * {@link TranslationBundle}
     *
     * @param locale
     *            the preferred locale
     */
    public static void setLocale(Locale locale) {
        local.set(new NLS(locale));
    }

    /**
     * Sets the JVM default locale as the locale for the calling thread.
     * <p>
     * Semantically this is equivalent to
     * <code>NLS.setLocale(Locale.getDefault())</code>.
     */
    public static void useJVMDefaultLocale() {
        useJVMDefaultInternal();
    }

    // TODO(ms): change signature of public useJVMDefaultLocale() in 5.0 to get
    // rid of this internal method
    private static NLS useJVMDefaultInternal() {
        NLS b = new NLS(Locale.getDefault());
        local.set(b);
        return b;
    }

    /**
     * Returns an instance of the translation bundle of the required type. All
     * public String fields of the bundle instance will get their values
     * injected as described in the
     * {@link org.eclipse.jgit.nls.TranslationBundle}.
     *
     * @param type
     *            required bundle type
     * @return an instance of the required bundle type
     * @exception TranslationBundleLoadingException
     *                see
     *                {@link org.eclipse.jgit.errors.TranslationBundleLoadingException}
     * @exception TranslationStringMissingException
     *                see
     *                {@link org.eclipse.jgit.errors.TranslationStringMissingException}
     */
    public static <T extends TranslationBundle> T getBundleFor(Class<T> type) {
        NLS b = local.get();
        if (b == null) {
            b = useJVMDefaultInternal();
        }
        return b.get(type);
    }

    final private Locale locale;
    final private ConcurrentHashMap<Class, TranslationBundle> map = new ConcurrentHashMap<>();

    private NLS(Locale locale) {
        this.locale = locale;
    }

    @SuppressWarnings("unchecked")
    private <T extends TranslationBundle> T get(Class<T> type) {
        TranslationBundle bundle = map.get(type);
        if (bundle == null) {
            bundle = GlobalBundleCache.lookupBundle(locale, type);
            // There is a small opportunity for a race, which we may
            // lose. Accept defeat and return the winner's instance.
            TranslationBundle old = map.putIfAbsent(type, bundle);
            if (old != null)
                bundle = old;
        }
        return (T) bundle;
    }
}