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 org.apache.commons.discovery.ResourceNameDiscover;
020    import org.apache.commons.discovery.ResourceNameIterator;
021    
022    
023    /**
024     * Helper class for methods implementing the ResourceNameDiscover interface.
025     * 
026     * @author Richard A. Sitze
027     */
028    public abstract class ResourceNameDiscoverImpl implements ResourceNameDiscover
029    {
030        /**
031         * Locate names of resources that are bound to <code>resourceName</code>.
032         * 
033         * @return ResourceNameIterator
034         */
035        public abstract ResourceNameIterator findResourceNames(String resourceName);
036    
037        /**
038         * Locate names of resources that are bound to <code>resourceName</code>.
039         * 
040         * @return ResourceNameIterator
041         */
042        public ResourceNameIterator findResourceNames(final ResourceNameIterator inputNames) {
043            return new ResourceNameIterator() {
044                private ResourceNameIterator resourceNames = null;
045                private String resourceName = null;
046                
047                public boolean hasNext() {
048                    if (resourceName == null) {
049                        resourceName = getNextResourceName();
050                    }
051                    return resourceName != null;
052                }
053                
054                public String nextResourceName() {
055                    String name = resourceName;
056                    resourceName = null;
057                    return name;
058                }
059                
060                private String getNextResourceName() {
061                    while (inputNames.hasNext() && (resourceNames == null  ||  !resourceNames.hasNext())) {
062                        resourceNames =
063                            findResourceNames(inputNames.nextResourceName());
064                    }
065        
066                    return (resourceNames != null  &&  resourceNames.hasNext())
067                           ? resourceNames.nextResourceName()
068                           : null;
069                }
070            };
071        }
072    }