1   /**
2    *  Copyright 2003-2007 Greg Luck
3    *
4    *  Licensed under the Apache License, Version 2.0 (the "License");
5    *  you may not use this file except in compliance with the License.
6    *  You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   *  Unless required by applicable law or agreed to in writing, software
11   *  distributed under the License is distributed on an "AS IS" BASIS,
12   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   *  See the License for the specific language governing permissions and
14   *  limitations under the License.
15   */
16  
17  package net.sf.ehcache.constructs.blocking;
18  
19  /**
20   * A cache entry factory that blocks until signaled.
21   * <p/>
22   * This is useful for writing tests.
23   *
24   * @author Greg Luck
25   * @version $Id: BlockingCacheEntryFactory.java 512 2007-07-10 09:18:45Z gregluck $
26   */
27  public class BlockingCacheEntryFactory implements CacheEntryFactory {
28  
29      private final Object value;
30      private int count;
31  
32      /**
33       * Constructs a new object
34       * @param value the factory always creates values equal to this value
35       */
36      public BlockingCacheEntryFactory(final Object value) {
37          this.value = value;
38      }
39  
40  
41      /**
42       * @return number of entries the factory has created.
43       */
44      public int getCount() {
45          return count;
46      }
47  
48  
49      /**
50       * Signals the factory.
51       */
52      public synchronized void signal(final int count) {
53          this.count += count;
54          notify();
55      }
56  
57      /**
58       * Fetches an entry.
59       */
60      public synchronized Object createEntry(final Object key) throws Exception {
61          // Wait until signalled
62          while (count == 0) {
63              wait();
64          }
65          count--;
66          return value;
67      }
68  }