001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.discovery.resource.names;
018
019import java.util.ArrayList;
020import java.util.List;
021
022import org.apache.commons.discovery.ResourceNameDiscover;
023import org.apache.commons.discovery.ResourceNameIterator;
024import org.apache.commons.logging.Log;
025import org.apache.commons.logging.LogFactory;
026
027/**
028 * Holder for multiple ResourceNameDiscover instances.
029 *
030 * The result is the union of the results from each
031 * (not a chained sequence, where results feed the next in line.
032 */
033public class NameDiscoverers extends ResourceNameDiscoverImpl implements ResourceNameDiscover {
034
035    private static Log log = LogFactory.getLog(NameDiscoverers.class);
036
037    /**
038     * Sets the {@code Log} for this class.
039     *
040     * @param _log This class {@code Log}
041     * @deprecated This method is not thread-safe
042     */
043    @Deprecated
044    public static void setLog(Log _log) {
045        log = _log;
046    }
047
048    private final List<ResourceNameDiscover> discoverers = new ArrayList<ResourceNameDiscover>();
049
050    /**
051     *  Construct a new resource name discoverer
052     */
053    public NameDiscoverers() {
054    }
055
056    /**
057     * Specify an discover to be used in searching.
058     * The order of discover determines the order of the result.
059     * It is recommended to add the most specific discover first.
060     *
061     * @param discover The discover to be added
062     */
063    public void addResourceNameDiscover(ResourceNameDiscover discover) {
064        if (discover != null) {
065            discoverers.add(discover);
066        }
067    }
068
069    /**
070     * Retrieve the discover positioned at the given index.
071     *
072     * @param idx The discover index position client is requiring
073     * @return The discover positioned at the input index
074     */
075    protected ResourceNameDiscover getResourceNameDiscover(int idx) {
076        return discoverers.get(idx);
077    }
078
079    /**
080     * Returns the current size of set discovers.
081     *
082     * @return The current size of set discovers
083     */
084    protected int size() {
085        return discoverers.size();
086    }
087
088    /**
089     * {@inheritDoc}
090     */
091    @Override
092    public ResourceNameIterator findResourceNames(final String resourceName) {
093        if (log.isDebugEnabled()) {
094            log.debug("find: resourceName='" + resourceName + "'");
095        }
096
097        return new ResourceNameIterator() {
098
099            private int idx = 0;
100
101            private ResourceNameIterator iterator = null;
102
103            public boolean hasNext() {
104                if (iterator == null  ||  !iterator.hasNext()) {
105                    iterator = getNextIterator();
106                    if (iterator == null) {
107                        return false;
108                    }
109                }
110                return iterator.hasNext();
111            }
112
113            public String nextResourceName() {
114                return iterator.nextResourceName();
115            }
116
117            private ResourceNameIterator getNextIterator() {
118                while (idx < size()) {
119                    ResourceNameIterator iter =
120                        getResourceNameDiscover(idx++).findResourceNames(resourceName);
121
122                    if (iter.hasNext()) {
123                        return iter;
124                    }
125                }
126                return null;
127            }
128        };
129    }
130
131}