messageresourcesfactory.java

structs源码

/*
 * $Id: MessageResourcesFactory.java 471754 2006-11-06 14:55:09Z husted $
 *
 * 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 org.apache.struts.config.MessageResourcesConfig;

import java.io.Serializable;

/**
 * Factory for <code>MessageResources</code> instances.  The general usage
 * pattern for this class is:
 *
 * <ul>
 *
 * <li>Call <code>MessageResourcesFactory().createFactory()</code> to retrieve
 * a <code>MessageResourcesFactory</code> instance.</li> <li>Set properties as
 * required to configure this factory instance to create
 * <code>MessageResources</code> instances with desired characteristics.</li>
 *
 * <li>Call the <code>createResources()</code> method of the factory to
 * retrieve a newly instantiated <code>MessageResources</code> instance.</li>
 *
 * </ul>
 *
 * @version $Rev: 471754 $ $Date: 2005-08-29 23:57:50 -0400 (Mon, 29 Aug 2005)
 *          $
 */
public abstract class MessageResourcesFactory implements Serializable {
    // ------------------------------------------------------ Static Properties

    /**
     * The Java class to be used for <code>MessageResourcesFactory</code>
     * instances.
     */
    protected static transient Class clazz = null;

    /**
     * Commons Logging instance.
     */
    private static Log LOG = LogFactory.getLog(MessageResourcesFactory.class);

    /**
     * The fully qualified class name to be used for <code>MessageResourcesFactory</code>
     * instances.
     */
    protected static String factoryClass =
        "org.apache.struts.util.PropertyMessageResourcesFactory";

    // ---------------------------------------------------- Instance Properties

    /**
     * Configuration information for Message Resources.
     */
    protected MessageResourcesConfig config;

    /**
     * The "return null" property value to which newly created
     * MessageResourcess should be initialized.
     */
    protected boolean returnNull = true;

    /**
     * Set the configuration information for Message Resources.
     *
     * @since Struts 1.2.8
     */
    public MessageResourcesConfig getConfig() {
        return config;
    }

    /**
     * Return the configuration information for Message Resources.
     *
     * @since Struts 1.2.8
     */
    public void setConfig(MessageResourcesConfig config) {
        this.config = config;
    }

    /**
     * Get default value of the "returnNull" property used to initialize newly
     * created MessageResourcess.
     *
     * @return default value of the "returnNull" property newly created
     *         MessageResourcess are initialized to.
     */
    public boolean getReturnNull() {
        return (this.returnNull);
    }

    /**
     * Set the default value of the "returnNull" property newly created
     * MessageResourcess are initialized to.
     *
     * @param returnNull default value of the "returnNull" MessageResourcess
     *                   are initialized to.
     */
    public void setReturnNull(boolean returnNull) {
        this.returnNull = returnNull;
    }

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

    /**
     * Create and return a newly instansiated <code>MessageResources</code>.
     * This method must be implemented by concrete subclasses.
     *
     * @param config Configuration parameter(s) for the requested bundle
     */
    public abstract MessageResources createResources(String config);

    /**
     * The fully qualified class name that is used for <code>MessageResourcesFactory</code>
     * instances.
     *
     * @return class name that is used for <code>MessageResourcesFactory</code>
     *         instances
     */
    public static String getFactoryClass() {
        return (MessageResourcesFactory.factoryClass);
    }

    /**
     * Set the fully qualified class name that is used for
     * <code>MessageResourcesFactory</code> instances.
     *
     * @param factoryClass name that is used for <code>MessageResourcesFactory</code>
     *                     instances
     */
    public static void setFactoryClass(String factoryClass) {
        MessageResourcesFactory.factoryClass = factoryClass;
        MessageResourcesFactory.clazz = null;
    }

    // --------------------------------------------------------- Static Methods

    /**
     * Create and return a <code>MessageResourcesFactory</code> instance of
     * the appropriate class, which can be used to create customized
     * <code>MessageResources</code> instances.  If no such factory can be
     * created, return <code>null</code> instead.
     */
    public static MessageResourcesFactory createFactory() {
        // Construct a new instance of the specified factory class
        try {
            if (clazz == null) {
                clazz = RequestUtils.applicationClass(factoryClass);
            }

            MessageResourcesFactory factory =
                (MessageResourcesFactory) clazz.newInstance();

            return (factory);
        } catch (Throwable t) {
            LOG.error("MessageResourcesFactory.createFactory", t);

            return (null);
        }
    }
}