1 /**
2 * JDBM LICENSE v1.00
3 *
4 * Redistribution and use of this software and associated documentation
5 * ("Software"), with or without modification, are permitted provided
6 * that the following conditions are met:
7 *
8 * 1. Redistributions of source code must retain copyright
9 * statements and notices. Redistributions must also contain a
10 * copy of this document.
11 *
12 * 2. Redistributions in binary form must reproduce the
13 * above copyright notice, this list of conditions and the
14 * following disclaimer in the documentation and/or other
15 * materials provided with the distribution.
16 *
17 * 3. The name "JDBM" must not be used to endorse or promote
18 * products derived from this Software without prior written
19 * permission of Cees de Groot. For written permission,
20 * please contact cg@cdegroot.com.
21 *
22 * 4. Products derived from this Software may not be called "JDBM"
23 * nor may "JDBM" appear in their names without prior written
24 * permission of Cees de Groot.
25 *
26 * 5. Due credit should be given to the JDBM Project
27 * (http://jdbm.sourceforge.net/).
28 *
29 * THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS
30 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
31 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
32 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
33 * CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
34 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
35 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
36 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
38 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
39 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
40 * OF THE POSSIBILITY OF SUCH DAMAGE.
41 *
42 * Copyright 2000 (C) Cees de Groot. All Rights Reserved.
43 * Contributions are Copyright (C) 2000 by their associated contributors.
44 *
45 * $Id: CachePolicy.java,v 1.5 2003/11/01 13:25:02 dranatunga Exp $
46 */
47
48 package jdbm.helper;
49
50 import java.util.Enumeration;
51
52 /**
53 * CachePolicity is an abstraction for different cache policies.
54 * (ie. MRU, time-based, soft-refs, ...)
55 *
56 * @author <a href="mailto:boisvert@intalio.com">Alex Boisvert</a>
57 * @author <a href="mailto:dranatunga@users.sourceforge.net">Dilum Ranatunga</a>
58 * @version $Id: CachePolicy.java,v 1.5 2003/11/01 13:25:02 dranatunga Exp $
59 */
60 public interface CachePolicy
61 {
62
63 /**
64 * Place an object in the cache. If the cache does not currently contain
65 * an object for the key specified, this mapping is added. If an object
66 * currently exists under the specified key, the current object is
67 * replaced with the new object.
68 * <p>
69 * If the changes to the cache cause the eviction of any objects
70 * <strong>stored under other key(s)</strong>, events corresponding to
71 * the evictions are fired for each object. If an event listener is
72 * unable to handle the eviction, and throws a cache eviction exception,
73 * that exception is propagated to the caller. If such an exception is
74 * thrown, the cache itself should be left as it was before the
75 * <code>put()</code> operation was invoked: the the object whose
76 * eviction failed is still in the cache, and the new insertion or
77 * modification is reverted.
78 *
79 * @param key key for the cached object
80 * @param value the cached object
81 * @throws CacheEvictionException propagated if, while evicting objects
82 * to make room for new object, an eviction listener encountered
83 * this problem.
84 */
85 public void put( Object key, Object value )
86 throws CacheEvictionException;
87
88
89 /**
90 * Obtain the object stored under the key specified.
91 *
92 * @param key key the object was cached under
93 * @return the object if it is still in the cache, null otherwise.
94 */
95 public Object get( Object key );
96
97
98 /**
99 * Remove the object stored under the key specified. Note that since
100 * eviction notices are only fired when objects under <strong>different
101 * keys</strong> are evicted, no event is fired for any object stored
102 * under this key (see {@link #put(Object, Object) put( )}).
103 *
104 * @param key key the object was stored in the cache under.
105 */
106 public void remove( Object key );
107
108
109 /**
110 * Remove all objects from the cache. Consistent with
111 * {@link #remove(Object) remove( )}, no eviction notices are fired.
112 */
113 public void removeAll();
114
115
116 /**
117 * Enumerate through the objects currently in the cache.
118 */
119 public Enumeration elements();
120
121
122 /**
123 * Add a listener to this cache policy.
124 * <p>
125 * If this cache policy already contains a listener that is equal to
126 * the one being added, this call has no effect.
127 *
128 * @param listener the (non-null) listener to add to this policy
129 * @throws IllegalArgumentException if listener is null.
130 */
131 public void addListener( CachePolicyListener listener )
132 throws IllegalArgumentException;
133
134
135 /**
136 * Remove a listener from this cache policy. The listener is found
137 * using object equality, not identity.
138 *
139 * @param listener the listener to remove from this policy
140 */
141 public void removeListener( CachePolicyListener listener );
142
143 }