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/* $Id: WithDefaultsRulesWrapper.java 729104 2008-12-23 20:45:23Z rahul $
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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;

import java.util.ArrayList;
import java.util.List;

/**
 * 

Rules Decorator that returns default rules * when no matches are returned by the wrapped implementation.

* *

This allows default Rule instances to be added to any * existing Rules implementation. These default Rule * instances will be returned for any match for which the wrapped * implementation does not return any matches.

*

For example, *

 *   Rule alpha;
 *   ...
 *   WithDefaultsRulesWrapper rules = new WithDefaultsRulesWrapper(new BaseRules());
 *   rules.addDefault(alpha);
 *   ...
 *   digester.setRules(rules);
 *   ...
 * 
* when a pattern does not match any other rule, then rule alpha will be called. *

*

WithDefaultsRulesWrapper follows the Decorator pattern.

* * @since 1.6 */ public class WithDefaultsRulesWrapper implements Rules { // --------------------------------------------------------- Fields /** The Rules implementation that this class wraps. */ private Rules wrappedRules; /** Rules to be fired when the wrapped implementations returns none. */ private List defaultRules = new ArrayList(); /** All rules (preserves order in which they were originally added) */ private List allRules = new ArrayList(); // --------------------------------------------------------- Constructor /** * Base constructor. * * @param wrappedRules the wrapped Rules implementation, not null * @throws IllegalArgumentException when wrappedRules is null */ public WithDefaultsRulesWrapper(Rules wrappedRules) { if (wrappedRules == null) { throw new IllegalArgumentException("Wrapped rules must not be null"); } this.wrappedRules = wrappedRules; } // --------------------------------------------------------- Properties /** Gets digester using these Rules */ public Digester getDigester() { return wrappedRules.getDigester(); } /** Sets digeseter using these Rules */ public void setDigester(Digester digester) { wrappedRules.setDigester(digester); for (Rule rule : defaultRules) { rule.setDigester(digester); } } /** Gets namespace to apply to Rule's added */ public String getNamespaceURI() { return wrappedRules.getNamespaceURI(); } /** Sets namespace to apply to Rule's added subsequently */ public void setNamespaceURI(String namespaceURI) { wrappedRules.setNamespaceURI(namespaceURI); } /** Gets Rule's which will be fired when the wrapped implementation returns no matches */ public List getDefaults() { return defaultRules; } // --------------------------------------------------------- Public Methods public List match(String pattern) { return match("", pattern); } /** * Return list of rules matching given pattern. * If wrapped implementation returns any matches return those. * Otherwise, return default matches. */ public List match(String namespaceURI, String pattern) { List matches = wrappedRules.match(namespaceURI, pattern); if (matches == null || matches.isEmpty()) { // a little bit of defensive programming return new ArrayList(defaultRules); } // otherwise return matches; } /** Adds a rule to be fired when wrapped implementation returns no matches */ public void addDefault(Rule rule) { // set up rule if (wrappedRules.getDigester() != null) { rule.setDigester(wrappedRules.getDigester()); } if (wrappedRules.getNamespaceURI() != null) { rule.setNamespaceURI(wrappedRules.getNamespaceURI()); } defaultRules.add(rule); allRules.add(rule); } /** Gets all rules */ public List rules() { return allRules; } /** Clears all Rule's */ public void clear() { wrappedRules.clear(); allRules.clear(); defaultRules.clear(); } /** * Adds a Rule to be fired on given pattern. * Pattern matching is delegated to wrapped implementation. */ public void add(String pattern, Rule rule) { wrappedRules.add(pattern, rule); allRules.add(rule); } }




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