| /* $Id: RuleFinder.java,v 1.5 2004/05/10 06:36:38 skitching Exp $ |
| * |
| * Copyright 2004 The Apache Software Foundation. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package org.apache.commons.digester.plugins; |
| |
| import java.util.Properties; |
| import org.apache.commons.digester.Digester; |
| |
| /** |
| * Each concrete implementation of RuleFinder is an algorithm for |
| * locating a source of digester rules for a plugin. The algorithm may |
| * use info explicitly provided by the user as part of the plugin |
| * declaration, or not (in which case the concrete RuleFinder subclass |
| * typically has Dflt as part of its name). |
| * <p> |
| * Instances of this class can also be regarded as a Factory for RuleLoaders, |
| * except that an instance of a RuleLoader is only created if the particular |
| * finder algorithm can locate a suitable source of rules given the plugin |
| * class and associated properties. |
| * <p> |
| * This is an abstract class rather than an interface in order to make |
| * it possible to enhance this class in future without breaking binary |
| * compatibility; it is possible to add methods to an abstract class, but |
| * not to an interface. |
| * |
| * @since 1.6 |
| */ |
| |
| public abstract class RuleFinder { |
| |
| /** |
| * Apply the finder algorithm to attempt to locate a source of |
| * digester rules for the specified plugin class. |
| * <p> |
| * This method is invoked when a plugin is declared by the user, either |
| * via an explicit use of PluginDeclarationRule, or implicitly via an |
| * "inline declaration" where the declaration and use are simultaneous. |
| * <p> |
| * If dynamic rules for the specified plugin class are located, then |
| * the RuleFinder will return a RuleLoader object encapsulating those |
| * rules, and this object will be invoked each time the user actually |
| * requests an instance of the declared plugin class, to load the |
| * custom rules associated with that plugin instance. |
| * <p> |
| * If no dynamic rules can be found, null is returned. This is not an |
| * error; merely an indication that this particular algorithm found |
| * no matches. |
| * <p> |
| * The properties object holds any xml attributes the user may have |
| * specified on the plugin declaration in order to indicate how to locate |
| * the plugin rules. |
| * <p> |
| * @throws PluginConfigurationException if the algorithm finds a source |
| * of rules, but there is something invalid about that source. |
| */ |
| |
| public abstract RuleLoader findLoader( |
| Digester d, Class pluginClass, |
| Properties p) throws PluginException; |
| } |
| |