001 /**
002 * JDBM LICENSE v1.00
003 *
004 * Redistribution and use of this software and associated documentation
005 * ("Software"), with or without modification, are permitted provided
006 * that the following conditions are met:
007 *
008 * 1. Redistributions of source code must retain copyright
009 * statements and notices. Redistributions must also contain a
010 * copy of this document.
011 *
012 * 2. Redistributions in binary form must reproduce the
013 * above copyright notice, this list of conditions and the
014 * following disclaimer in the documentation and/or other
015 * materials provided with the distribution.
016 *
017 * 3. The name "JDBM" must not be used to endorse or promote
018 * products derived from this Software without prior written
019 * permission of Cees de Groot. For written permission,
020 * please contact cg@cdegroot.com.
021 *
022 * 4. Products derived from this Software may not be called "JDBM"
023 * nor may "JDBM" appear in their names without prior written
024 * permission of Cees de Groot.
025 *
026 * 5. Due credit should be given to the JDBM Project
027 * (http://jdbm.sourceforge.net/).
028 *
029 * THIS SOFTWARE IS PROVIDED BY THE JDBM PROJECT AND CONTRIBUTORS
030 * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
031 * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
032 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
033 * CEES DE GROOT OR ANY CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
034 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
035 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
036 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
037 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
038 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
039 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
040 * OF THE POSSIBILITY OF SUCH DAMAGE.
041 *
042 * Copyright 2000 (C) Cees de Groot. All Rights Reserved.
043 * Contributions are Copyright (C) 2000 by their associated contributors.
044 *
045 * $Id: CachePolicy.java,v 1.5 2003/11/01 13:25:02 dranatunga Exp $
046 */
047
048 package jdbm.helper;
049
050 import java.util.Enumeration;
051
052 /**
053 * CachePolicity is an abstraction for different cache policies.
054 * (ie. MRU, time-based, soft-refs, ...)
055 *
056 * @author <a href="mailto:boisvert@intalio.com">Alex Boisvert</a>
057 * @author <a href="mailto:dranatunga@users.sourceforge.net">Dilum Ranatunga</a>
058 * @version $Id: CachePolicy.java,v 1.5 2003/11/01 13:25:02 dranatunga Exp $
059 */
060 public interface CachePolicy
061 {
062
063 /**
064 * Place an object in the cache. If the cache does not currently contain
065 * an object for the key specified, this mapping is added. If an object
066 * currently exists under the specified key, the current object is
067 * replaced with the new object.
068 * <p>
069 * If the changes to the cache cause the eviction of any objects
070 * <strong>stored under other key(s)</strong>, events corresponding to
071 * the evictions are fired for each object. If an event listener is
072 * unable to handle the eviction, and throws a cache eviction exception,
073 * that exception is propagated to the caller. If such an exception is
074 * thrown, the cache itself should be left as it was before the
075 * <code>put()</code> operation was invoked: the the object whose
076 * eviction failed is still in the cache, and the new insertion or
077 * modification is reverted.
078 *
079 * @param key key for the cached object
080 * @param value the cached object
081 * @throws CacheEvictionException propagated if, while evicting objects
082 * to make room for new object, an eviction listener encountered
083 * this problem.
084 */
085 public void put( Object key, Object value )
086 throws CacheEvictionException;
087
088
089 /**
090 * Obtain the object stored under the key specified.
091 *
092 * @param key key the object was cached under
093 * @return the object if it is still in the cache, null otherwise.
094 */
095 public Object get( Object key );
096
097
098 /**
099 * 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 }