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