propertymessageresources.java.svn-base

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 *
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.struts.util;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.IOException;
import java.io.InputStream;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Locale;
import java.util.Properties;

/**
 * Concrete subclass of <code>MessageResources</code> that reads message keys
 * and corresponding strings from named property resources in a <b><i>similar</i></b> manner
 * (see <i>modes</i> below) that <code>java.util.PropertyResourceBundle</code> does.  The
 * <code>base</code> property defines the base property resource name, and
 * must be specified. <p> <strong>IMPLEMENTATION NOTE</strong> - This class
 * trades memory for speed by caching all messages located via generalizing
 * the Locale under the original locale as well. This results in specific
 * messages being stored in the message cache more than once, but improves
 * response time on subsequent requests for the same locale + key
 * combination.
 *
 * <h2>Operating Modes</h2>
 * This implementation can be configured to operate in one of three modes:
 * <ul>
 *    <li>1. <b>Default</b> - default, backwardly compatible, Struts behaviour (i.e. the way
 *    its always worked).</li>
 *    <li>2. <b>JSTL</b> - compatible with how JSTL finds messages
 *        (fix for <a href="http://issues.apache.org/struts/browse/STR-2925">STR-2925</a>)</li>
 *    <li>3. <b>Resource</b> - compatible with how Java's <code>PropertyResourceBundle</code>
 *        finds messages (fix for
 *        <a href="http://issues.apache.org/struts/browse/STR-2077">STR-2077</a>)</li>
 * </ul>
 *
 * <h3>1. Default Mode</h3>
 * <i>Default mode</i> is the way this implementation has always operated. It searches
 * for a message key for property resources in the following sequence:
 * <pre>
 *      base + "_" + localeLanguage + "_" + localeCountry + "_" + localeVariant
 *      base + "_" + localeLanguage + "_" + localeCountry
 *      base + "_" + localeLanguage
 *      base + "_" + default locale
 *      base
 * </pre>
 * <p>
 * This mode is the <i>default</i> and requires no additional configuration.
 *
 * <h3>2. JSTL Mode</h3>
 * <i>JSTL mode</i> is compatible with how JSTL operates and the default Locale
 * is not used when looking for a message key. <i>JSTL mode</i> searches for
 * a message key for property resources in the following sequence:
 * <pre>
 *      base + "_" + localeLanguage + "_" + localeCountry + "_" + localeVariant
 *      base + "_" + localeLanguage + "_" + localeCountry
 *      base + "_" + localeLanguage
 *      base
 * </pre>
 * <p>
 * Configure <code>PropertyMessageResources</code> to operate in this mode by
 * specifying a value of <code>JSTL</code> for the <code>mode</code>
 * key in your <code>struts-config.xml</code>:
 * <pre>
 *      &lt;message-resources parameter="mypackage.MyMessageResources"&gt;
 *          &lt;set-property key="mode" value="JSTL"/&gt;
 *      &lt;/message-resources&gt;
 * </pre>
 *
 * <h3>3. Resource Mode</h3>
 * <i>Resource mode</i> is compatible with how Java's <code>PropertyResourceBundle</code>
 * operates. <i>Resource mode</i> searches first through the specified Locale's language,
 * country and variant, then through the default Locale's language,
 * country and variant and finally using just the <code>base</code>:
 * <pre>
 *      base + "_" + localeLanguage + "_" + localeCountry + "_" + localeVariant
 *      base + "_" + localeLanguage + "_" + localeCountry
 *      base + "_" + localeLanguage
 *      base + "_" + defaultLanguage + "_" + defaultCountry + "_" + defaultVariant
 *      base + "_" + defaultLanguage + "_" + defaultCountry
 *      base + "_" + defaultLanguage
 *      base
 * </pre>
 * <p>
 * Configure <code>PropertyMessageResources</code> to operate in this mode by
 * specifying a value of <code>resource</code> for the <code>mode</code>
 * key in your <code>struts-config.xml</code>:
 * <pre>
 *      &lt;message-resources parameter="mypackage.MyMessageResources"&gt;
 *          &lt;set-property key="mode" value="resource"/&gt;
 *      &lt;/message-resources&gt;
 * </pre>
 * 
 * @version $Rev$ $Date$
 */
public class PropertyMessageResources extends MessageResources {


    /** Indicates compatibility with how PropertyMessageResources has always looked up messages */
    private static final int MODE_DEFAULT = 0;

    /** Indicates compatibility with how JSTL looks up messages */
    private static final int MODE_JSTL = 1;

    /** Indicates compatibility with how java's PropertyResourceBundle looks up messages */
    private static final int MODE_RESOURCE_BUNDLE = 2;

    /**
     * The <code>Log</code> instance for this class.
     */
    protected static final Log log =
        LogFactory.getLog(PropertyMessageResources.class);

    // ------------------------------------------------------------- Properties

    /**
     * The set of locale keys for which we have already loaded messages, keyed
     * by the value calculated in <code>localeKey()</code>.
     */
    protected HashMap locales = new HashMap();

    /**
     * The cache of messages we have accumulated over time, keyed by the value
     * calculated in <code>messageKey()</code>.
     */
    protected HashMap messages = new HashMap();

    /**
     * Compatibility mode that PropertyMessageResources is operating in.
     */
    private int mode = MODE_DEFAULT;

    // ----------------------------------------------------------- Constructors

    /**
     * Construct a new PropertyMessageResources according to the specified
     * parameters.
     *
     * @param factory The MessageResourcesFactory that created us
     * @param config  The configuration parameter for this MessageResources
     */
    public PropertyMessageResources(MessageResourcesFactory factory,
        String config) {
        super(factory, config);
        log.trace("Initializing, config='" + config + "'");
    }

    /**
     * Construct a new PropertyMessageResources according to the specified
     * parameters.
     *
     * @param factory    The MessageResourcesFactory that created us
     * @param config     The configuration parameter for this
     *                   MessageResources
     * @param returnNull The returnNull property we should initialize with
     */
    public PropertyMessageResources(MessageResourcesFactory factory,
        String config, boolean returnNull) {
        super(factory, config, returnNull);
        log.trace("Initializing, config='" + config + "', returnNull="
            + returnNull);
    }

    // --------------------------------------------------------- Public Methods

    /**
     * Set the compatibility mode this implementation uses for message lookup.
     *
     * @param mode <code>JSTL</code> for JSTL compatibility,
     *  <code>resource</code> for PropertyResourceBundle compatibility or
     *  <code>default</code> for Struts backward compatibility.
     */
    public void setMode(String mode) {
        String value = (mode == null ? null : mode.trim());
        if ("jstl".equalsIgnoreCase(value)) {
            this.mode = MODE_JSTL;
            if (log.isDebugEnabled()) {
                log.info("Operating in JSTL compatible mode [" + mode + "]");
            }
        } else if ("resource".equalsIgnoreCase(value)) {
            this.mode = MODE_RESOURCE_BUNDLE;
            if (log.isDebugEnabled()) {
                log.info("Operating in PropertyResourceBundle compatible mode [" + mode + "]");
            }
        } else {
            this.mode = MODE_DEFAULT;
            if (log.isDebugEnabled()) {
                log.info("Operating in Default mode [" + mode + "]");
            }
        }
    }

    /**
     * Returns a text message for the specified key, for the specified or default
     * Locale. A null string result will be returned by this method if no relevant
     * message resource is found for this key or Locale, if the
     * <code>returnNull</code> property is set.  Otherwise, an appropriate
     * error message will be returned. <p> This method must be implemented by
     * a concrete subclass.
     *
     * @param locale The requested message Locale, or <code>null</code> for
     *               the system default Locale
     * @param key    The message key to look up
     * @return text message for the specified key and locale
     */
    public String getMessage(Locale locale, String key) {
        if (log.isDebugEnabled()) {
            log.debug("getMessage(" + locale + "," + key + ")");