001/* $Id: FinderFromDfltMethod.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.util.Properties;
021import java.lang.reflect.Method;
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 method with a specific name
030 * on the plugin class.
031 *
032 * @since 1.6
033 */
034
035public class FinderFromDfltMethod extends RuleFinder {
036    public static String DFLT_METHOD_NAME = "addRules";
037
038    private String methodName;
039    
040    /** See {@link #findLoader}. */
041    public FinderFromDfltMethod() { 
042        this(DFLT_METHOD_NAME);
043    }
044
045    /**
046     * Create a rule-finder which invokes a specific method on the plugin
047     * class whenever dynamic rules for a plugin need to be loaded. See the 
048     * findRules method for more info.
049     *
050     * @param methodName must be non-null.
051     */
052    public FinderFromDfltMethod(String methodName) { 
053        this.methodName = methodName;
054    }
055    
056    /**
057     * If there exists on the plugin class a method with name matching the 
058     * constructor's methodName value then locate the appropriate Method on 
059     * the plugin class and return an object encapsulating that info.
060     * <p>
061     * If there is no matching method then just return null.
062     * <p>
063     * The returned object (when non-null) will invoke the target method
064     * on the plugin class whenever its addRules method is invoked. The
065     * target method is expected to have the following prototype:
066     * <code> public static void xxxxx(Digester d, String patternPrefix); </code>
067     */
068    @Override
069    public RuleLoader findLoader(Digester d, Class<?> pluginClass, Properties p)
070                        throws PluginException {
071
072        Method rulesMethod = LoaderFromClass.locateMethod(pluginClass, methodName);
073        if (rulesMethod == null) {
074            return null;
075        }
076        
077        return new LoaderFromClass(pluginClass, rulesMethod);
078    }
079}
080