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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
****************************************************************/
package org.apache.cayenne.cache;
import java.io.Serializable;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.apache.cayenne.CayenneRuntimeException;
import org.apache.cayenne.query.QueryMetadata;
import org.apache.commons.collections.map.LRUMap;
/**
* A default implementation of the {@link QueryCache} interface that stores data in a
* non-expiring LRUMap.
*
* @since 3.0
*/
public class MapQueryCache implements QueryCache, Serializable {
public static final int DEFAULT_CACHE_SIZE = 2000;
protected Map<String, CacheEntry> map;
public MapQueryCache() {
this(DEFAULT_CACHE_SIZE);
}
public MapQueryCache(int maxSize) {
this.map = new LRUMap(maxSize);
}
@SuppressWarnings("unchecked")
public List get(QueryMetadata metadata) {
String key = metadata.getCacheKey();
if (key == null) {
return null;
}
CacheEntry entry;
synchronized (this) {
entry = map.get(key);
}
return (entry != null) ? entry.list : null;
}
/**
* Returns a non-null cached value. If it is not present in the cache, it is obtained
* by calling {@link QueryCacheEntryFactory#createObject()} without blocking the cache. As
* a result there is a potential of multiple threads to be updating cache in parallel -
* this wouldn't lead to corruption of the cache, but can be suboptimal.
*/
@SuppressWarnings("unchecked")
public List get(QueryMetadata metadata, QueryCacheEntryFactory factory) {
List result = get(metadata);
if (result == null) {
Object newObject = factory.createObject();
if (!(newObject instanceof List)) {
if (newObject == null) {
throw new CayenneRuntimeException("Null on cache rebuilding: "
+ metadata.getCacheKey());
}
else {
throw new CayenneRuntimeException(
"Invalid query result, expected List, got "
+ newObject.getClass().getName());
}
}
result = (List) newObject;
put(metadata, result);
}
return result;
}
@SuppressWarnings("unchecked")
public void put(QueryMetadata metadata, List results) {
String key = metadata.getCacheKey();
if (key != null) {
CacheEntry entry = new CacheEntry();
entry.list = results;
entry.cacheGroups = metadata.getCacheGroups();
synchronized (this) {
map.put(key, entry);
}
}
}
public void remove(String key) {
if (key != null) {
synchronized (this) {
map.remove(key);
}
}
}
public void removeGroup(String groupKey) {
if (groupKey != null) {
synchronized (this) {
Iterator<CacheEntry> it = map.values().iterator();
while (it.hasNext()) {
CacheEntry entry = it.next();
if (entry.cacheGroups != null) {
for (int i = 0; i < entry.cacheGroups.length; i++) {
if (groupKey.equals(entry.cacheGroups[i])) {
it.remove();
break;
}
}
}
}
}
}
}
public void clear() {
synchronized (this) {
map.clear();
}
}
public int size() {
return map.size();
}
final static class CacheEntry implements Serializable {
List<?> list;
String[] cacheGroups;
}
}