Commons Digester example source code file (RulesBase.java)

This example Commons Digester source code file (RulesBase.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, deprecated, digester, hashmap, list, list, rule, rule, rules, rulesbase, string, string, util

The Commons Digester RulesBase.java source code

/* $Id: RulesBase.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.HashMap;
import java.util.List;


/**
 * <p>Default implementation of the Rules interface that supports
 * the standard rule matching behavior.  This class can also be used as a
 * base class for specialized <code>Rules implementations.

 *
 * <p>The matching policies implemented by this class support two different
 * types of pattern matching rules:</p>
 * <ul>
 * <li>Exact Match - A pattern "a/b/c" exactly matches a
 *     <code><c> element, nested inside a <b>
 *     element, which is nested inside an <code><a> element.
 * <li>Tail Match - A pattern "*/a/b" matches a
 *     <code><b> element, nested inside an <a>
 *      element, no matter how deeply the pair is nested.</li>
 * </ul>
 *
 * <p>Note that wildcard patterns are ignored if an explicit match can be found 
 * (and when multiple wildcard patterns match, only the longest, ie most 
 * explicit, pattern is considered a match).</p>
 *
 * <p>See the package documentation for package org.apache.commons.digester 
 * for more information.</p>
 */

public class RulesBase implements Rules {


    // ----------------------------------------------------- Instance Variables


    /**
     * The set of registered Rule instances, keyed by the matching pattern.
     * Each value is a List containing the Rules for that pattern, in the
     * order that they were orginally registered.
     */
    protected HashMap<String, List cache = new HashMap>();


    /**
     * The Digester instance with which this Rules instance is associated.
     */
    protected Digester digester = null;


    /**
     * The namespace URI for which subsequently added <code>Rule
     * objects are relevant, or <code>null for matching independent
     * of namespaces.
     */
    protected String namespaceURI = null;


    /**
     * The set of registered Rule instances, in the order that they were
     * originally registered.
     */
    protected ArrayList<Rule> rules = new ArrayList();


    // ------------------------------------------------------------- Properties


    /**
     * Return the Digester instance with which this Rules instance is
     * associated.
     */
    public Digester getDigester() {

        return (this.digester);

    }


    /**
     * Set the Digester instance with which this Rules instance is associated.
     *
     * @param digester The newly associated Digester instance
     */
    public void setDigester(Digester digester) {

        this.digester = digester;
        for (Rule rule : rules) {
            rule.setDigester(digester);
        }

    }


    /**
     * Return the namespace URI that will be applied to all subsequently
     * added <code>Rule objects.
     */
    public String getNamespaceURI() {

        return (this.namespaceURI);

    }


    /**
     * Set the namespace URI that will be applied to all subsequently
     * added <code>Rule objects.
     *
     * @param namespaceURI Namespace URI that must match on all
     *  subsequently added rules, or <code>null for matching
     *  regardless of the current namespace URI
     */
    public void setNamespaceURI(String namespaceURI) {

        this.namespaceURI = namespaceURI;

    }


    // --------------------------------------------------------- Public Methods


    /**
     * Register a new Rule instance matching the specified pattern.
     *
     * @param pattern Nesting pattern to be matched for this Rule
     * @param rule Rule instance to be registered
     */
    public void add(String pattern, Rule rule) {
        // to help users who accidently add '/' to the end of their patterns
        int patternLength = pattern.length();
        if (patternLength>1 && pattern.endsWith("/")) {
            pattern = pattern.substring(0, patternLength-1);
        }
        
        
        List<Rule> list = cache.get(pattern);
        if (list == null) {
            list = new ArrayList<Rule>();
            cache.put(pattern, list);
        }
        list.add(rule);
        rules.add(rule);
        if (this.digester != null) {
            rule.setDigester(this.digester);
        }
        if (this.namespaceURI != null) {
            rule.setNamespaceURI(this.namespaceURI);
        }

    }


    /**
     * Clear all existing Rule instance registrations.
     */
    public void clear() {

        cache.clear();
        rules.clear();

    }


    /**
     * Return a List of all registered Rule instances that match the specified
     * nesting pattern, or a zero-length List if there are no matches.  If more
     * than one Rule instance matches, they <strong>must be returned
     * in the order originally registered through the <code>add()
     * method.
     *
     * @param pattern Nesting pattern to be matched
     *
     * @deprecated Call match(namespaceURI,pattern) instead.
     */
    @Deprecated
    public List<Rule> match(String pattern) {

        return (match(null, pattern));

    }


    /**
     * Return a List of all registered Rule instances that match the specified
     * nesting pattern, or a zero-length List if there are no matches.  If more
     * than one Rule instance matches, they <strong>must be returned
     * in the order originally registered through the <code>add()
     * method.
     *
     * @param namespaceURI Namespace URI for which to select matching rules,
     *  or <code>null to match regardless of namespace URI
     * @param pattern Nesting pattern to be matched
     */
    public List<Rule> match(String namespaceURI, String pattern) {

        // List rulesList = (List) this.cache.get(pattern);
        List<Rule> rulesList = lookup(namespaceURI, pattern);
        if ((rulesList == null) || (rulesList.size() < 1)) {
            // Find the longest key, ie more discriminant
            String longKey = "";
            for (String key : cache.keySet()) {
                if (key.startsWith("*/")) {
                    if (pattern.equals(key.substring(2)) ||
                        pattern.endsWith(key.substring(1))) {
                        if (key.length() > longKey.length()) {
                            // rulesList = (List) this.cache.get(key);
                            rulesList = lookup(namespaceURI, key);
                            longKey = key;
                        }
                    }
                }
            }
        }
        if (rulesList == null) {
            rulesList = new ArrayList<Rule>();
        }
        return (rulesList);

    }


    /**
     * Return a List of all registered Rule instances, or a zero-length List
     * if there are no registered Rule instances.  If more than one Rule
     * instance has been registered, they <strong>must be returned
     * in the order originally registered through the <code>add()
     * method.
     */
    public List<Rule> rules() {

        return (this.rules);

    }


    // ------------------------------------------------------ Protected Methods


    /**
     * Return a List of Rule instances for the specified pattern that also
     * match the specified namespace URI (if any).  If there are no such
     * rules, return <code>null.
     *
     * @param namespaceURI Namespace URI to match, or <code>null to
     *  select matching rules regardless of namespace URI
     * @param pattern Pattern to be matched
     */
    protected List<Rule> lookup(String namespaceURI, String pattern) {

        // Optimize when no namespace URI is specified
        List<Rule> list = this.cache.get(pattern);
        if (list == null) {
            return (null);
        }
        if ((namespaceURI == null) || (namespaceURI.length() == 0)) {
            return (list);
        }

        // Select only Rules that match on the specified namespace URI
        ArrayList<Rule> results = new ArrayList();
        for (Rule item : list) {
            if ((namespaceURI.equals(item.getNamespaceURI())) ||
                    (item.getNamespaceURI() == null)) {
                results.add(item);
            }
        }
        return (results);

    }


}