001 /* $Id: FinderFromMethod.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 org.apache.commons.digester.Digester;
022 import org.apache.commons.digester.plugins.RuleFinder;
023 import org.apache.commons.digester.plugins.RuleLoader;
024 import org.apache.commons.digester.plugins.PluginException;
025
026 /**
027 * A rule-finding algorithm which expects the caller to specify a methodname
028 * as a plugin property, where the method exists on the plugin class.
029 *
030 * @since 1.6
031 */
032
033 public class FinderFromMethod extends RuleFinder {
034 /**
035 * Xml attribute that needs to be present on a plugin declaration
036 * in order to specify the method to load rules from.
037 */
038 public static String DFLT_METHOD_ATTR = "method";
039
040 /** See {@link #findLoader}. */
041 private String methodAttr;
042
043 /** Constructor. */
044 public FinderFromMethod() {
045 this(DFLT_METHOD_ATTR);
046 }
047
048 /** See {@link #findLoader}. */
049 public FinderFromMethod(String methodAttr) {
050 this.methodAttr = methodAttr;
051 }
052
053 /**
054 * If there exists a property with the name matching constructor param
055 * methodAttr, then locate the appropriate Method on the plugin class
056 * and return an object encapsulating that info.
057 * <p>
058 * If there is no matching property provided, then just return null.
059 * <p>
060 * The returned object (when non-null) will invoke the target method
061 * on the plugin class whenever its addRules method is invoked. The
062 * target method is expected to have the following prototype:
063 * <code> public static void xxxxx(Digester d, String patternPrefix); </code>
064 */
065 @Override
066 public RuleLoader findLoader(Digester d, Class<?> pluginClass, Properties p)
067 throws PluginException {
068
069 String methodName = p.getProperty(methodAttr);
070 if (methodName == null) {
071 // nope, user hasn't requested dynamic rules to be loaded
072 // from a specific class.
073 return null;
074 }
075
076 return new LoaderFromClass(pluginClass, methodName);
077 }
078 }
079