001/* $Id: FinderFromDfltClass.java 992106 2010-09-02 20:29:25Z 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.util.Properties;
021import org.apache.commons.digester.Digester;
022import org.apache.commons.digester.plugins.RuleFinder;
023import org.apache.commons.digester.plugins.RuleLoader;
024import org.apache.commons.digester.plugins.PluginException;
025
026/**
027 * A rule-finding algorithm which looks for a method with a specific name
028 * on a class whose name is derived from the plugin class name.
029 *
030 * @since 1.6
031 */
032
033public class FinderFromDfltClass extends RuleFinder {
034    public static String DFLT_RULECLASS_SUFFIX = "RuleInfo";
035    public static String DFLT_METHOD_NAME = "addRules";
036    
037    private String rulesClassSuffix;
038    private String methodName;
039    
040    /** See {@link #findLoader}. */
041    public FinderFromDfltClass() {
042        this(DFLT_RULECLASS_SUFFIX, DFLT_METHOD_NAME);
043    }
044    
045    /**
046     * Create a rule-finder which invokes a method on a class whenever 
047     * dynamic rules for a plugin need to be loaded. See the findRules 
048     * method for more info.
049     *
050     * @param rulesClassSuffix must be non-null.
051     * @param methodName may be null.
052     */
053     public FinderFromDfltClass(String rulesClassSuffix, String methodName) { 
054        this.rulesClassSuffix = rulesClassSuffix;
055        this.methodName = methodName;
056    }
057    
058    /**
059     * If there exists a class whose name is the plugin class name + the
060     * suffix specified to the constructor, then load that class, locate 
061     * the appropriate rules-adding method on that class, and return an 
062     * object encapsulating that info.
063     * <p>
064     * If there is no such class, then just return null.
065     * <p>
066     * The returned object (when non-null) will invoke the target method
067     * on the selected class whenever its addRules method is invoked. The
068     * target method is expected to have the following prototype:
069     * <code> public static void xxxxx(Digester d, String patternPrefix); </code>
070     */
071    @Override
072    public RuleLoader findLoader(Digester digester, Class<?> pluginClass, Properties p)
073                            throws PluginException {
074
075        String rulesClassName = pluginClass.getName() + rulesClassSuffix;
076
077        Class<?> rulesClass = null;
078        try {
079            rulesClass = digester.getClassLoader().loadClass(rulesClassName);
080        } catch(ClassNotFoundException cnfe) {
081            // nope, no rule-info class in the classpath
082            return null;
083        }
084
085        if (methodName == null) {
086            methodName = DFLT_METHOD_NAME;
087        }
088        
089        return new LoaderFromClass(rulesClass, methodName);
090    }
091}
092