/**
* 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 storm.trident.state.map;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import storm.trident.util.LRUMap;
/**
* Useful to layer over a map that communicates with a database. you generally layer opaque map over this over your database store
*
* @author nathan
* @param <T>
*/
public class CachedMap<T> implements IBackingMap<T> {
LRUMap<List<Object>, T> _cache;
IBackingMap<T> _delegate;
public CachedMap(IBackingMap<T> delegate, int cacheSize) {
_cache = new LRUMap<List<Object>, T>(cacheSize);
_delegate = delegate;
}
@Override
public List<T> multiGet(List<List<Object>> keys) {
Map<List<Object>, T> results = new HashMap<List<Object>, T>();
List<List<Object>> toGet = new ArrayList<List<Object>>();
for (List<Object> key : keys) {
if (_cache.containsKey(key)) {
results.put(key, _cache.get(key));
} else {
toGet.add(key);
}
}
List<T> fetchedVals = _delegate.multiGet(toGet);
for (int i = 0; i < toGet.size(); i++) {
List<Object> key = toGet.get(i);
T val = fetchedVals.get(i);
_cache.put(key, val);
results.put(key, val);
}
List<T> ret = new ArrayList<T>(keys.size());
for (List<Object> key : keys) {
ret.add(results.get(key));
}
return ret;
}
@Override
public void multiPut(List<List<Object>> keys, List<T> values) {
cache(keys, values);
_delegate.multiPut(keys, values);
}
private void cache(List<List<Object>> keys, List<T> values) {
for (int i = 0; i < keys.size(); i++) {
_cache.put(keys.get(i), values.get(i));
}
}
}