de.kaiserpfalzEdv.commons.HandleI18NImpl.java Source code

Introduction

Here is the source code for de.kaiserpfalzEdv.commons.HandleI18NImpl.java

Source

/*
 * Copyright 2015 Kaiserpfalz EDV-Service Roland Lichti
 *
 * 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 de.kaiserpfalzEdv.commons;

import de.kaiserpfalzEdv.commons.jee.Closeable;
import de.kaiserpfalzEdv.commons.jee.Initializable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;
import java.io.Serializable;
import java.text.MessageFormat;
import java.util.Locale;
import java.util.MissingResourceException;
import java.util.Properties;
import java.util.ResourceBundle;

import static com.google.common.base.Preconditions.checkArgument;
import static org.apache.commons.lang3.StringUtils.isNotBlank;

/**
 * This class handles the internationalization via message bundles.
 *
 * @author klenkes
 * @since 1.0.0
 */
public class HandleI18NImpl implements Initializable, Closeable, HandleI18N, Serializable {
    /**
     * Serial UID of this class.
     */
    private static final long serialVersionUID = -5193578993565207464L;

    /**
     * The minimum number of characters in a filename for the I18N handler.
     */
    public static final int MIN_FILE_NAME_LENGTH = 4;
    /**
     * The maximum number of characters in a filename for the I18N handler.
     */
    public static final int MAX_FILE_NAME_LENGTH = 500;

    /**
     * Default logger.
     */
    private static final Logger LOG = LoggerFactory.getLogger(HandleI18NImpl.class);

    /**
     * The java resource bundle used for retrieving the messages.
     */
    private transient ResourceBundle messageBundle = null;

    /**
     * The filename (basename) of the property file containing the translations.
     */
    @NotNull
    @Size(min = MIN_FILE_NAME_LENGTH, max = MAX_FILE_NAME_LENGTH)
    private String i18nFileName = null;

    /**
     * The locale for this translation handler.
     */
    @NotNull
    private Locale locale = null;

    /**
     * Creates a new instance of this handler.
     *
     * @param i18nFileName The filename of the jave resource bundle.
     * @param locale       the locale for this handler.
     * @throws IllegalArgumentException if the filename or the locale is NULL or
     *                                  the filename is empty.
     */
    public HandleI18NImpl(final String i18nFileName, final Locale locale) {
        checkArgument(isNotBlank(i18nFileName), "i18nFileName must not be empty");
        checkArgument(locale != null, "locale must be set (null is not allowed)");

        this.i18nFileName = i18nFileName;
        this.locale = locale;
    }

    @Override
    public void init() {
    }

    @Override
    public void init(final Properties props) {
    }

    @Override
    public void close() {
    }

    /**
     * Sets the name of the localization resource bundle file.
     *
     * @param i18nFileName The filename of the resource bundle.
     * @throws IllegalArgumentException if the file name given is NULl or empty.
     */
    public void setI18NFileName(@NotNull final String i18nFileName) {
        checkArgument(i18nFileName != null && !i18nFileName.isEmpty(), "i18nFileName must not be empty");

        //noinspection ConstantConditions
        if (!i18nFileName.equals(this.i18nFileName)) {
            LOG.trace("Setting message bundle file name to '{}'", i18nFileName);

            this.i18nFileName = i18nFileName;

            resetMessageBundle();
        }
    }

    /**
     * Retrieves the filename for this localization resource bundle file.
     *
     * @return The name set for this resource bundle file.
     */
    public String getI18NFileName() {
        return i18nFileName;
    }

    @Override
    public void setLocale(@NotNull final Locale locale) {
        checkArgument(locale != null, "locale must be not null");

        //noinspection ConstantConditions
        if (!locale.equals(this.locale)) {
            LOG.trace("Setting locale to '{}'.", locale.getDisplayName());

            this.locale = locale;

            resetMessageBundle();
        }
    }

    @Override
    public Locale getLocale() {
        return locale;
    }

    /**
     * Initializes the message bundle (if not already initialized). This is our lazy loading ...
     *
     * @return The message bundle.
     */
    private ResourceBundle getMessageBundle() {
        if (messageBundle == null) {
            messageBundle = ResourceBundle.getBundle(i18nFileName, locale);
        }

        return messageBundle;
    }

    /**
     * Clears our resource bundle cache.
     */
    private void resetMessageBundle() {
        ResourceBundle.clearCache();
        messageBundle = null;
    }

    @Override
    public String get(final String key) {
        checkArgument(isNotBlank(key), "key must not be empty");

        String result;

        try {
            result = getMessageBundle().getString(key);
        } catch (MissingResourceException e) {
            LOG.warn("Could not find resource string '{}' in resource bundle file '{}'. Returning '{}' instead.",
                    key, i18nFileName, key);

            result = key;
        }

        return result;
    }

    @Override
    public String get(final String key, final Object[] parameters) {
        MessageFormat message = new MessageFormat(get(key));
        message.setLocale(locale);

        LOG.debug("Translating {}='{}' with parameters: {} ...", key, get(key), parameters);

        return message.format(parameters);
    }
}