%line | %branch | |||||||||
---|---|---|---|---|---|---|---|---|---|---|
org.apache.turbine.util.BufferCache |
|
|
1 | package org.apache.turbine.util; |
|
2 | ||
3 | /* |
|
4 | * Copyright 2001-2005 The Apache Software Foundation. |
|
5 | * |
|
6 | * Licensed under the Apache License, Version 2.0 (the "License") |
|
7 | * you may not use this file except in compliance with the License. |
|
8 | * You may obtain a copy of the License at |
|
9 | * |
|
10 | * http://www.apache.org/licenses/LICENSE-2.0 |
|
11 | * |
|
12 | * Unless required by applicable law or agreed to in writing, software |
|
13 | * distributed under the License is distributed on an "AS IS" BASIS, |
|
14 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
|
15 | * See the License for the specific language governing permissions and |
|
16 | * limitations under the License. |
|
17 | */ |
|
18 | ||
19 | import org.apache.commons.collections.SequencedHashMap; |
|
20 | ||
21 | /** |
|
22 | * A fixed length object cache implementing the LRU algorithm. Convenient for |
|
23 | * buffering recently used objects. |
|
24 | * |
|
25 | * @author <a href="mailto:dlr@collab.net">Daniel Rall</a> |
|
26 | * @author <a href="mailto:hps@intermeta.de">Henning P. Schmiedehausen</a> |
|
27 | * @version $Id: BufferCache.java 278822 2005-09-05 19:53:05Z henning $ |
|
28 | */ |
|
29 | public class BufferCache |
|
30 | extends SequencedHashMap |
|
31 | { |
|
32 | /** Serial Version UID */ |
|
33 | private static final long serialVersionUID = 5206274963401520445L; |
|
34 | ||
35 | /** |
|
36 | * The default maximum cache size. |
|
37 | */ |
|
38 | private static final int DEFAULT_MAX_SIZE = 35; |
|
39 | ||
40 | /** |
|
41 | * The size of the cache. The newest elements in the sequence are kept |
|
42 | * toward the end. |
|
43 | */ |
|
44 | private int maxSize; |
|
45 | ||
46 | /** |
|
47 | * Creates a new instance with default storage buffer pre-allocated. |
|
48 | */ |
|
49 | public BufferCache() |
|
50 | { |
|
51 | 0 | this(DEFAULT_MAX_SIZE); |
52 | 0 | } |
53 | ||
54 | /** |
|
55 | * Creates a new instance with the specified storage buffer pre-allocated. |
|
56 | * |
|
57 | * @param maxSize The maximum size of the cache. |
|
58 | */ |
|
59 | public BufferCache(int maxSize) |
|
60 | { |
|
61 | 0 | super(maxSize); |
62 | 0 | this.maxSize = maxSize; |
63 | 0 | } |
64 | ||
65 | /** |
|
66 | * Stores the provided key/value pair, freshening its list index if the |
|
67 | * specified key already exists. |
|
68 | * |
|
69 | * @param key The key to the provided value. |
|
70 | * @param value The value to store. |
|
71 | * @return The previous value for the specified key, or |
|
72 | * <code>null</code> if none. |
|
73 | */ |
|
74 | public synchronized Object put(Object key, Object value) |
|
75 | { |
|
76 | 0 | int size = size(); |
77 | 0 | if (size > 0 && size + 1 >= maxSize) |
78 | { |
|
79 | // Stay within constraints of allocated buffer by releasing the |
|
80 | // eldest buffered object. |
|
81 | 0 | remove(0); |
82 | } |
|
83 | 0 | return super.put(key, value); |
84 | } |
|
85 | ||
86 | /** |
|
87 | * Retrieves the value associated with the provided key, freshening the |
|
88 | * sequence of the key as well. |
|
89 | * |
|
90 | * @param key The key whose value to retrieve. |
|
91 | * @return The keyed value. |
|
92 | */ |
|
93 | public synchronized Object get(Object key) |
|
94 | { |
|
95 | 0 | return super.get(key); |
96 | } |
|
97 | } |
This report is generated by jcoverage, Maven and Maven JCoverage Plugin. |