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: */package jdbm.helper;
047:
048: import java.util.Enumeration;
049:
050: /**
051: * CachePolicity is an abstraction for different cache policies.
052: * (ie. MRU, time-based, soft-refs, ...)
053: *
054: * @author <a href="mailto:boisvert@intalio.com">Alex Boisvert</a>
055: * @author <a href="mailto:dranatunga@users.sourceforge.net">Dilum Ranatunga</a>
056: * @version $Id: CachePolicy.java,v 1.5 2003/11/01 13:25:02 dranatunga Exp $
057: */
058: public interface CachePolicy {
059:
060: /**
061: * Place an object in the cache. If the cache does not currently contain
062: * an object for the key specified, this mapping is added. If an object
063: * currently exists under the specified key, the current object is
064: * replaced with the new object.
065: * <p>
066: * If the changes to the cache cause the eviction of any objects
067: * <strong>stored under other key(s)</strong>, events corresponding to
068: * the evictions are fired for each object. If an event listener is
069: * unable to handle the eviction, and throws a cache eviction exception,
070: * that exception is propagated to the caller. If such an exception is
071: * thrown, the cache itself should be left as it was before the
072: * <code>put()</code> operation was invoked: the the object whose
073: * eviction failed is still in the cache, and the new insertion or
074: * modification is reverted.
075: *
076: * @param key key for the cached object
077: * @param value the cached object
078: * @throws CacheEvictionException propagated if, while evicting objects
079: * to make room for new object, an eviction listener encountered
080: * this problem.
081: */
082: public void put(Object key, Object value)
083: throws CacheEvictionException;
084:
085: /**
086: * Obtain the object stored under the key specified.
087: *
088: * @param key key the object was cached under
089: * @return the object if it is still in the cache, null otherwise.
090: */
091: public Object get(Object key);
092:
093: /**
094: * Remove the object stored under the key specified. Note that since
095: * eviction notices are only fired when objects under <strong>different
096: * keys</strong> are evicted, no event is fired for any object stored
097: * under this key (see {@link #put(Object, Object) put( )}).
098: *
099: * @param key key the object was stored in the cache under.
100: */
101: public void remove(Object key);
102:
103: /**
104: * Remove all objects from the cache. Consistent with
105: * {@link #remove(Object) remove( )}, no eviction notices are fired.
106: */
107: public void removeAll();
108:
109: /**
110: * Enumerate through the objects currently in the cache.
111: */
112: public Enumeration elements();
113:
114: /**
115: * Add a listener to this cache policy.
116: * <p>
117: * If this cache policy already contains a listener that is equal to
118: * the one being added, this call has no effect.
119: *
120: * @param listener the (non-null) listener to add to this policy
121: * @throws IllegalArgumentException if listener is null.
122: */
123: public void addListener(CachePolicyListener listener)
124: throws IllegalArgumentException;
125:
126: /**
127: * Remove a listener from this cache policy. The listener is found
128: * using object equality, not identity.
129: *
130: * @param listener the listener to remove from this policy
131: */
132: public void removeListener(CachePolicyListener listener);
133:
134: }
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