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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package org.apache.commons.discovery.resource.classes;
18  
19  import org.apache.commons.discovery.ResourceClass;
20  import org.apache.commons.discovery.ResourceClassDiscover;
21  import org.apache.commons.discovery.ResourceClassIterator;
22  import org.apache.commons.discovery.ResourceIterator;
23  import org.apache.commons.discovery.ResourceNameIterator;
24  import org.apache.commons.discovery.resource.ClassLoaders;
25  import org.apache.commons.discovery.resource.ResourceDiscoverImpl;
26  
27  /**
28   * Default {@link ResourceClassDiscover} implementation.
29   *
30   * @param <T> The SPI type
31   */
32  public abstract class ResourceClassDiscoverImpl<T> extends ResourceDiscoverImpl implements ResourceClassDiscover<T> {
33  
34      /**
35       * Construct a new resource discoverer.
36       */
37      public ResourceClassDiscoverImpl() {
38          super();
39      }
40  
41      /**
42       * Construct a new resource discoverer.
43       *
44       * @param classLoaders The class loaders holder
45       */
46      public ResourceClassDiscoverImpl(ClassLoaders classLoaders) {
47          super(classLoaders);
48      }
49  
50      /**
51       * {@inheritDoc}
52       */
53      @Override
54      public ResourceNameIterator findResourceNames(String resourceName) {
55          return findResourceClasses(resourceName);
56      }
57  
58      /**
59       * {@inheritDoc}
60       */
61      @Override
62      public ResourceNameIterator findResourceNames(ResourceNameIterator resourceNames) {
63          return findResourceClasses(resourceNames);
64      }
65  
66      /**
67       * {@inheritDoc}
68       */
69      @Override
70      public ResourceIterator findResources(String resourceName) {
71          return findResourceClasses(resourceName);
72      }
73  
74      /**
75       * {@inheritDoc}
76       */
77      @Override
78      public ResourceIterator findResources(ResourceNameIterator resourceNames) {
79          return findResourceClasses(resourceNames);
80      }
81  
82      /**
83       * Locate class resources that are bound to <code>className</code>.
84       *
85       * @param className The class name has to be located
86       * @return The located resources iterator
87       */
88      public abstract ResourceClassIterator<T> findResourceClasses(String className);
89  
90      /**
91       * Locate class resources that are bound to {@code resourceNames}.
92       *
93       * @param inputNames The resource name iterator
94       * @return a new {@link ResourceClassIterator} over the given resource name iterator
95       */
96      public ResourceClassIterator<T> findResourceClasses(final ResourceNameIterator inputNames) {
97          return new ResourceClassIterator<T>() {
98              private ResourceClassIterator<T> classes = null;
99              private ResourceClass<T> resource = null;
100 
101             public boolean hasNext() {
102                 if (resource == null) {
103                     resource = getNextResource();
104                 }
105                 return resource != null;
106             }
107 
108             @Override
109             public ResourceClass<T> nextResourceClass() {
110                 ResourceClass<T> rsrc = resource;
111                 resource = null;
112                 return rsrc;
113             }
114 
115             private ResourceClass<T> getNextResource() {
116                 while (inputNames.hasNext() &&
117                        (classes == null  ||  !classes.hasNext())) {
118                     classes =
119                         findResourceClasses(inputNames.nextResourceName());
120                 }
121 
122                 return (classes != null  &&  classes.hasNext())
123                        ? classes.nextResourceClass()
124                        : null;
125             }
126         };
127     }
128 
129 }