/*****************************************************************
* 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 org.apache.cayenne.query.QueryMetadata;
import org.apache.cayenne.query.QueryMetadataProxy;
import java.util.List;
/**
* A {@link QueryCache} wrapper that introduces a key namespace on top of a
* delegate shared cache. This way multiple cache users can share the same
* underlying cache without a possibility of key conflicts, yet refresh the
* cache groups in a coordinated fashion.
*
* @since 3.0
*/
public class NestedQueryCache implements QueryCache {
// the idea is to be something short (to speed up comparisons), but clear
// and unlikely to create a conflict with application cache keys...
// fully-qualified class name that we used before was a bit too long
private static final String NAMESPACE_PREXIX = "#nested-";
private static volatile int currentId;
protected QueryCache delegate;
protected String namespace;
private static final int nextInt() {
if (currentId == Integer.MAX_VALUE) {
currentId = 0;
}
return currentId++;
}
public NestedQueryCache(QueryCache delegate) {
this.delegate = delegate;
this.namespace = NAMESPACE_PREXIX + nextInt() + ":";
}
/**
* Returns the actual implementation of the query cache that is wrapped by
* this NestedQueryCache.
*/
public QueryCache getDelegate() {
return delegate;
}
/**
* Clears the underlying shared cache.
* @see QueryCache#clear()
* @deprecated since 4.0
*/
@Override
@Deprecated
public void clear() {
// seems pretty evil - it clears the keys that do not belong to our subset of the cache
delegate.clear();
}
@Override
@SuppressWarnings("rawtypes")
public List get(QueryMetadata metadata, QueryCacheEntryFactory factory) {
return delegate.get(qualifiedMetadata(metadata), factory);
}
@Override
@SuppressWarnings("rawtypes")
public List get(QueryMetadata metadata) {
return delegate.get(qualifiedMetadata(metadata));
}
@Override
@SuppressWarnings("rawtypes")
public void put(QueryMetadata metadata, List results) {
delegate.put(qualifiedMetadata(metadata), results);
}
/**
* Removes an entry for key in the current namespace.
*/
@Override
public void remove(String key) {
delegate.remove(qualifiedKey(key));
}
/**
* Invalidates a shared cache group.
*/
@Override
public void removeGroup(String groupKey) {
delegate.removeGroup(groupKey);
}
@Override
public void removeGroup(String groupKey, Class<?> keyType, Class<?> valueType) {
delegate.removeGroup(groupKey, keyType, valueType);
}
/**
* Returns a shared cache size.
* @see QueryCache#size()
* @deprecated since 4.0
*/
@Override
@Deprecated
public int size() {
return delegate.size();
}
private String qualifiedKey(String key) {
return key != null ? namespace + key : null;
}
private QueryMetadata qualifiedMetadata(QueryMetadata md) {
return new QueryMetadataProxy(md) {
@Override
public String getCacheKey() {
return qualifiedKey(mdDelegate.getCacheKey());
}
};
}
}