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 */
017 package org.apache.commons.discovery.resource.names;
018
019 import java.util.ArrayList;
020 import java.util.List;
021
022 import org.apache.commons.discovery.ResourceNameDiscover;
023 import org.apache.commons.discovery.ResourceNameIterator;
024 import org.apache.commons.logging.Log;
025 import 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 */
033 public 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 }