001/* $Id: FinderFromDfltResource.java 992060 2010-09-02 19:09:47Z simonetripodi $
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one or more
004 * contributor license agreements.  See the NOTICE file distributed with
005 * this work for additional information regarding copyright ownership.
006 * The ASF licenses this file to You under the Apache License, Version 2.0
007 * (the "License"); you may not use this file except in compliance with
008 * the License.  You may obtain a copy of the License at
009 *
010 *      http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.commons.digester.plugins.strategies;
019
020import java.io.InputStream;
021import java.util.Properties;
022
023import org.apache.commons.digester.Digester;
024import org.apache.commons.digester.plugins.RuleFinder;
025import org.apache.commons.digester.plugins.RuleLoader;
026import org.apache.commons.digester.plugins.PluginException;
027
028/**
029 * A rule-finding algorithm which looks for a resource file in the classpath
030 * whose name is derived from the plugin class name plus a specified suffix.
031 * <p>
032 * If the resource-file is found, then it is expected to define a set of
033 * Digester rules in xmlrules format.
034 *
035 * @since 1.6
036 */
037
038public class FinderFromDfltResource extends RuleFinder {
039    public static String DFLT_RESOURCE_SUFFIX = "RuleInfo.xml";
040
041    private String resourceSuffix;
042    
043    /** See {@link #findLoader}. */
044    public FinderFromDfltResource() { 
045        this(DFLT_RESOURCE_SUFFIX);
046    }
047
048    /**
049     * Create a rule-finder which can load an xmlrules file, cache
050     * the rules away, and later add them as a plugin's custom rules
051     * when that plugin is referenced.
052     *
053     * @param resourceSuffix must be non-null.
054     */
055    public FinderFromDfltResource(String resourceSuffix) { 
056        this.resourceSuffix = resourceSuffix;
057    }
058    
059    /**
060     * If there exists a resource file whose name is equal to the plugin
061     * class name + the suffix specified in the constructor, then
062     * load that file, run it through the xmlrules module and return an object 
063     * encapsulating those rules.
064     * <p>
065     * If there is no such resource file, then just return null.
066     * <p>
067     * The returned object (when non-null) will add the selected rules to
068     * the digester whenever its addRules method is invoked.
069     */
070    @Override
071    public RuleLoader findLoader(Digester d, Class<?> pluginClass, Properties p)
072                        throws PluginException {
073
074        String resourceName = 
075            pluginClass.getName().replace('.', '/') 
076                    + resourceSuffix;
077            
078        InputStream is = 
079            pluginClass.getClassLoader().getResourceAsStream(
080                resourceName);
081
082        if (is == null) {
083            // ok, no such resource
084            return null;
085        }
086
087        return FinderFromResource.loadRules(d, pluginClass, is, resourceName);
088    }
089}
090