001 /* $Id: FinderFromDfltClass.java 729125 2008-12-23 21:21:07Z rahul $ 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 */ 018 019 package org.apache.commons.digester.plugins.strategies; 020 021 import java.util.Properties; 022 import org.apache.commons.digester.Digester; 023 import org.apache.commons.digester.plugins.RuleFinder; 024 import org.apache.commons.digester.plugins.RuleLoader; 025 import org.apache.commons.digester.plugins.PluginException; 026 027 /** 028 * A rule-finding algorithm which looks for a method with a specific name 029 * on a class whose name is derived from the plugin class name. 030 * 031 * @since 1.6 032 */ 033 034 public class FinderFromDfltClass extends RuleFinder { 035 public static String DFLT_RULECLASS_SUFFIX = "RuleInfo"; 036 public static String DFLT_METHOD_NAME = "addRules"; 037 038 private String rulesClassSuffix; 039 private String methodName; 040 041 /** See {@link #findLoader}. */ 042 public FinderFromDfltClass() { 043 this(DFLT_RULECLASS_SUFFIX, DFLT_METHOD_NAME); 044 } 045 046 /** 047 * Create a rule-finder which invokes a method on a class whenever 048 * dynamic rules for a plugin need to be loaded. See the findRules 049 * method for more info. 050 * 051 * @param rulesClassSuffix must be non-null. 052 * @param methodName may be null. 053 */ 054 public FinderFromDfltClass(String rulesClassSuffix, String methodName) { 055 this.rulesClassSuffix = rulesClassSuffix; 056 this.methodName = methodName; 057 } 058 059 /** 060 * If there exists a class whose name is the plugin class name + the 061 * suffix specified to the constructor, then load that class, locate 062 * the appropriate rules-adding method on that class, and return an 063 * object encapsulating that info. 064 * <p> 065 * If there is no such class, then just return null. 066 * <p> 067 * The returned object (when non-null) will invoke the target method 068 * on the selected class whenever its addRules method is invoked. The 069 * target method is expected to have the following prototype: 070 * <code> public static void xxxxx(Digester d, String patternPrefix); </code> 071 */ 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 // ok, ignore 082 } 083 084 if (rulesClass == null) { 085 // nope, no rule-info class in the classpath 086 return null; 087 } 088 089 if (methodName == null) { 090 methodName = DFLT_METHOD_NAME; 091 } 092 093 return new LoaderFromClass(rulesClass, methodName); 094 } 095 } 096