Commons Digester example source code file (WithDefaultsRulesWrapper.java)

This example Commons Digester source code file (WithDefaultsRulesWrapper.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Commons Digester tags/keywords

arraylist, arraylist, digester, illegalargumentexception, list, list, rule, rule, rules, string, string, util, withdefaultsruleswrapper, wrapped

The Commons Digester WithDefaultsRulesWrapper.java source code

/* $Id: WithDefaultsRulesWrapper.java 992060 2010-09-02 19:09:47Z simonetripodi $
 *
 * 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;

/**
 * <p>Rules Decorator that returns default rules 
 * when no matches are returned by the wrapped implementation.</p>
 *
 * <p>This allows default Rule instances to be added to any 
 * existing <code>Rules implementation. These default Rule 
 * instances will be returned for any match for which the wrapped 
 * implementation does not return any matches.</p>
 * <p> For example,
 * <pre>
 *   Rule alpha;
 *   ...
 *   WithDefaultsRulesWrapper rules = new WithDefaultsRulesWrapper(new BaseRules());
 *   rules.addDefault(alpha);
 *   ...
 *   digester.setRules(rules);
 *   ...
 * </pre>
 * when a pattern does not match any other rule, then rule alpha will be called.
 * </p>
 * <p>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<Rule> defaultRules = new ArrayList();
    /** All rules (preserves order in which they were originally added) */
    private List<Rule> allRules = new ArrayList();
    
    // --------------------------------------------------------- Constructor
    
    /** 
     * Base constructor.
     *
     * @param wrappedRules the wrapped <code>Rules implementation, not null
     * @throws IllegalArgumentException when <code>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<Rule> getDefaults() {
        return defaultRules;
    }
    
    // --------------------------------------------------------- Public Methods
    
    public List<Rule> 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<Rule> match(String namespaceURI, String pattern) {
        List<Rule> matches = wrappedRules.match(namespaceURI, pattern);
        if (matches ==  null || matches.isEmpty()) {
            // a little bit of defensive programming
            return new ArrayList<Rule>(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<Rule> 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);
    }
}