bundles/org.eclipse.e4.core.services/src/org/eclipse/e4/core/internal/services/ResourceBundleTranslationProvider.java

/*******************************************************************************
 * Copyright (c) 2012 Dirk Fauth and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Dirk Fauth <dirk.fauth@gmail.com> - initial API and implementation
 ******************************************************************************/
package org.eclipse.e4.core.internal.services;

import java.util.MissingResourceException;
import java.util.ResourceBundle;

/**
 * Wrapper class for accessing translations out of a {@link ResourceBundle}.
 *
 * @author Dirk Fauth
 *
 */
public class ResourceBundleTranslationProvider {

	/**
	 * The {@link ResourceBundle} to use for translations.
	 */
	private ResourceBundle resourceBundle;

	/**
	 *
	 * @param resourceBundle
	 *            The {@link ResourceBundle} to use for translations. Can be <code>null</code>,
	 *            which will lead to simply return the key modified by prefixing and suffixing it
	 *            with "!" when calling translate(String).
	 */
	public ResourceBundleTranslationProvider(ResourceBundle resourceBundle) {
		this.setResourceBundle(resourceBundle);
	}

	/**
	 * Tries to retrieve the translation value for the given key out of the {@link ResourceBundle}
	 * set to this {@link ResourceBundleTranslationProvider}. If there is no {@link ResourceBundle}
	 * set or there is no translation found for the given key, the key itself prefixed and suffixed
	 * with "!" will be returned to indicate that there is no translation found.
	 * <p>
	 * This implementation also supports the usage of dot separation for property keys. As in Java
	 * variables can not be separated with a dot, the underscore needs to be used for separation of
	 * the variable. This will be replaced automatically to a dot, if there is no translation found
	 * with an underscore as separator.
	 * </p>
	 * As per request, this implementation also supports camel cased member variables to match the
	 * appropriate property keys. The search order for the translation property key is as follows:
	 * <ol>
	 * <li>key = property key (no modification)</li>
	 * <li>underscorified key = property key (camel cased key is transformed to underscorified key)</li>
	 * <li>dot separated key = property key (underscorified key is transformed to dot separated key)
	 * </li>
	 * <li>nothing matches -&gt; return key prefixed and suffixed with "!"</li>
	 * </ol>
	 *
	 * @param key
	 *            The key of the requested translation property.
	 * @return The translation for the given key or the key itself prefixed and suffixed with "!" to
	 *         indicate that there is no translation available for the given key.
	 */
	public String translate(String key) {
		String result = ""; //$NON-NLS-1$
		try {
			if (this.resourceBundle == null) {
				result = "!" + key + "!"; //$NON-NLS-1$ //$NON-NLS-2$
			} else {
				// search for the key as is
				result = this.resourceBundle.getString(key);
			}
		} catch (MissingResourceException e) {
			// key was not found as is, check if it is camel cased
			String uKey = underscorify(key);
			if (!key.equals(uKey)) {
				// the underscorify method modified the key, so it seems it was camel cased
				result = translate(uKey);
			} else if (key.contains("_")) { //$NON-NLS-1$
				// underscorify didn't modify the key, but the key contains the underscore
				// so we check for the dot separated key
				result = translate(key.replace('_', '.'));
			} else {
				// nothing matched, so we return the key itself marked with !
				result = "!" + key + "!"; //$NON-NLS-1$ //$NON-NLS-2$
			}
		}
		return result;
	}

	/**
	 * @return The {@link ResourceBundle} that is used for translations.
	 */
	public ResourceBundle getResourceBundle() {
		return resourceBundle;
	}

	/**
	 * @param resourceBundle
	 *            The {@link ResourceBundle} to use for translations.
	 */
	public void setResourceBundle(ResourceBundle resourceBundle) {
		this.resourceBundle = resourceBundle;
	}

	/**
	 * This method is used to create a underscorified key out of a camel cased String.
	 * <p>
	 * Note: This method is introduced to support Java Naming Conventions for member variables,
	 * which says that member variables should be camel cased. See <a href=
	 * "http://www.oracle.com/technetwork/java/javase/documentation/codeconventions-135099.html#367"
	 * > Naming Conventions</a>.
	 *
	 * @param key
	 *            The possible camel cased key that needs to be underscorified.
	 * @return The underscorified key.
	 */
	public static String underscorify(String key) {
		if (key == null || key.isEmpty()) {
			return key;
		}

		StringBuilder result = new StringBuilder();
		for (int i = 0; i < key.length(); i++) {
			if (Character.isUpperCase(key.charAt(i))) {
				result.append("_").append(Character.toLowerCase(key.charAt(i))); //$NON-NLS-1$
			} else {
				result.append(key.charAt(i));
			}
		}
		return result.toString();
	}
}