Source Code Cross Referenced for ConcurrentQueryCache.java in  » Database-ORM » openjpa » org » apache » openjpa » datacache » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Database ORM » openjpa » org.apache.openjpa.datacache 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Licensed to the Apache Software Foundation (ASF) under one
003:         * or more contributor license agreements.  See the NOTICE file
004:         * distributed with this work for additional information
005:         * regarding copyright ownership.  The ASF licenses this file
006:         * to you under the Apache License, Version 2.0 (the
007:         * "License"); you may not use this file except in compliance
008:         * with the License.  You may obtain a copy of the License at
009:         *
010:         * http://www.apache.org/licenses/LICENSE-2.0
011:         *
012:         * Unless required by applicable law or agreed to in writing,
013:         * software distributed under the License is distributed on an
014:         * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015:         * KIND, either express or implied.  See the License for the
016:         * specific language governing permissions and limitations
017:         * under the License.    
018:         */
019:        package org.apache.openjpa.datacache;
020:
021:        import java.util.Collection;
022:
023:        import org.apache.openjpa.event.RemoteCommitListener;
024:        import org.apache.openjpa.util.CacheMap;
025:
026:        /**
027:         * A {@link QueryCache} implementation that is optimized for concurrent
028:         * access. When the cache fill up, values to remove from the cache are chosen
029:         * randomly. Due to race conditions, it is possible that a get call might not
030:         * retur a cached instance if that instance is being transferred between
031:         * internal datastructures.
032:         *
033:         * @since 0.4.1
034:         */
035:        public class ConcurrentQueryCache extends AbstractQueryCache implements 
036:                RemoteCommitListener {
037:
038:            private CacheMap _cache = newCacheMap();
039:
040:            /**
041:             * Returns the underlying {@link CacheMap} that this cache is using.
042:             * This is not an unmodifiable view on the map, so care should be taken
043:             * with this reference. Implementations should probably not modify the
044:             * contents of the cache, but should only use this reference
045:             * to obtain cache metrics. Additionally, this map may contain
046:             * expired data. Removal of timed-out data is done in a lazy
047:             * fashion, so the actual size of the map may be greater than the
048:             * number of non-expired query results in cache.
049:             */
050:            public CacheMap getCacheMap() {
051:                return _cache;
052:            }
053:
054:            /**
055:             * Returns the maximum number of unpinned objects to keep hard
056:             * references to.
057:             */
058:            public int getCacheSize() {
059:                return _cache.getCacheSize();
060:            }
061:
062:            /**
063:             * Sets the maximum number of unpinned objects to keep hard
064:             * references to. If the map contains more unpinned objects than
065:             * <code>size</code>, then this method will result in the cache
066:             * flushing old values.
067:             */
068:            public void setCacheSize(int size) {
069:                _cache.setCacheSize(size);
070:            }
071:
072:            /**
073:             * Returns the maximum number of unpinned objects to keep soft
074:             * references to. Defaults to <code>-1</code>.
075:             */
076:            public int getSoftReferenceSize() {
077:                return _cache.getSoftReferenceSize();
078:            }
079:
080:            /**
081:             * Sets the maximum number of unpinned objects to keep soft
082:             * references to. If the map contains more soft references than
083:             * <code>size</code>, then this method will result in the cache
084:             * flushing values.
085:             */
086:            public void setSoftReferenceSize(int size) {
087:                _cache.setSoftReferenceSize(size);
088:            }
089:
090:            public void initialize(DataCacheManager mgr) {
091:                super .initialize(mgr);
092:                conf.getRemoteCommitEventManager().addInternalListener(this );
093:            }
094:
095:            public void writeLock() {
096:                // delegate actually does nothing, but in case that changes...
097:                _cache.writeLock();
098:            }
099:
100:            public void writeUnlock() {
101:                // delegate actually does nothing, but in case that changes...
102:                _cache.writeUnlock();
103:            }
104:
105:            /**
106:             * Return the map to use as an internal cache.
107:             */
108:            protected CacheMap newCacheMap() {
109:                return new CacheMap();
110:            }
111:
112:            protected QueryResult getInternal(QueryKey qk) {
113:                return (QueryResult) _cache.get(qk);
114:            }
115:
116:            protected QueryResult putInternal(QueryKey qk, QueryResult result) {
117:                return (QueryResult) _cache.put(qk, result);
118:            }
119:
120:            protected QueryResult removeInternal(QueryKey qk) {
121:                return (QueryResult) _cache.remove(qk);
122:            }
123:
124:            protected void clearInternal() {
125:                _cache.clear();
126:            }
127:
128:            protected boolean pinInternal(QueryKey qk) {
129:                return _cache.pin(qk);
130:            }
131:
132:            protected boolean unpinInternal(QueryKey qk) {
133:                return _cache.unpin(qk);
134:            }
135:
136:            protected Collection keySet() {
137:                return _cache.keySet();
138:            }
139:        }
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