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 */
018 package org.apache.commons.digester.plugins.strategies;
019
020 import java.util.Properties;
021 import java.lang.reflect.Method;
022
023 import org.apache.commons.digester.Digester;
024 import org.apache.commons.digester.plugins.RuleFinder;
025 import org.apache.commons.digester.plugins.RuleLoader;
026 import 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
035 public 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