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Java > Open Source Codes > org > apache > geronimo > kernel > classloader > ResourceEnumeration


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.geronimo.kernel.classloader;
18
19 import java.util.Enumeration JavaDoc;
20 import java.util.Iterator JavaDoc;
21 import java.util.Collection JavaDoc;
22 import java.util.NoSuchElementException JavaDoc;
23
24 /**
25  * @version $Rev: 476049 $ $Date: 2006-11-16 23:35:17 -0500 (Thu, 16 Nov 2006) $
26  */
27 public class ResourceEnumeration implements Enumeration JavaDoc {
28     private Iterator JavaDoc iterator;
29     private final String JavaDoc resourceName;
30     private Object JavaDoc next;
31
32     public ResourceEnumeration(Collection JavaDoc resourceLocations, String JavaDoc resourceName) {
33         this.iterator = resourceLocations.iterator();
34         this.resourceName = resourceName;
35     }
36
37     public boolean hasMoreElements() {
38         fetchNext();
39         return (next != null);
40     }
41
42     public Object JavaDoc nextElement() {
43         fetchNext();
44
45         // save next into a local variable and clear the next field
46 Object JavaDoc next = this.next;
47         this.next = null;
48
49         // if we didn't have a next throw an exception
50 if (next == null) {
51             throw new NoSuchElementException JavaDoc();
52         }
53         return next;
54     }
55
56     private void fetchNext() {
57         if (iterator == null) {
58             return;
59         }
60         if (next != null) {
61             return;
62         }
63
64         try {
65             while (iterator.hasNext()) {
66                 ResourceLocation resourceLocation = (ResourceLocation) iterator.next();
67                 ResourceHandle resourceHandle = resourceLocation.getResourceHandle(resourceName);
68                 if (resourceHandle != null) {
69                     next = resourceHandle.getUrl();
70                     return;
71                 }
72             }
73             // no more elements
74 // clear the iterator so it can be GCed
75 iterator = null;
76         } catch (IllegalStateException JavaDoc e) {
77             // Jar file was closed... this means the resource finder was destroyed
78 // clear the iterator so it can be GCed
79 iterator = null;
80             throw e;
81         }
82     }
83 }
84
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