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/*
* Copyright (c) 2006 Israfil Consulting Services Corporation
* Copyright (c) 2006 Christian Edward Gruber
* All Rights Reserved
*
* This software is licensed under the Berkeley Standard Distribution license,
* (BSD license), as defined below:
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. Neither the name of Israfil Consulting Services nor the names of its contributors
* may be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* $Id: GenericCache.java 129 2006-12-31 23:20:02Z cgruber $
*/
package net.israfil.foundation.caching;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* A non-thread-safe cache object
*
* @author <a href="mailto:cgruber@israfil.net">Christian Edward Gruber</a>
*/
public class GenericFetcherCache implements FetcherCache {
private Map<String,Object> _caches = new HashMap<String,Object>();
/**
* Retrieves an object from a path in the cache
* @param cacheName A string identifying from which cache the object will be retrieved
* @param An array of path items identifying the path through the map keys.
*/
public Object get(Fetcher fetcher, String cacheName, String itemKey, String ... path) {
// Fetch the map containing the item.
Map<String,Object> cache = _getLocationInMap(_caches,new ArrayList<String>(_prepPathList(cacheName,path)));
// Get the item from the map
Object o = cache.get((itemKey==null) ? "__NULL__" : itemKey);
if (o == null) {
// Item doesn't exist, so try to fetch, then retrieve again.
fetcher.fetch();
o = cache.get((itemKey==null) ? "__NULL__" : itemKey);
}
return o;
}
/**
* A method to set values within the cache, to be used by Fetcher implementations
* in setting up the cache when they fetch.
*/
public void set(String cacheName, String itemKey, Object value, String ... path) {
List<String> pathList = _prepPathList(cacheName,path);
Map<String,Object> cache = _getLocationInMap(_caches,new ArrayList<String>(pathList));
cache.put(itemKey,value);
}
/**
* Creates a List that contains the pathelements, starting from the
* cache name down to the bottom, but excluding the actual final path
* item.
*/
static List<String> _prepPathList(String cacheName,String[] pathElements) {
List<String> pathList;
if (pathElements == null || pathElements.length < 1) {
pathList = new ArrayList<String>();
} else {
// Need to make this explicitly an arrayList, so that
// add(index,value) will work.
pathList = new ArrayList<String>(Arrays.asList(pathElements));
}
pathList.add(0,cacheName);
return pathList;
}
/**
* Recursively traverses the cache map, creating maps at path locations
* where they do not already exist.
*/
@SuppressWarnings("unchecked")
static Map<String, Object> _getLocationInMap(
Map<String, Object> currentMap, List<String> cachePath) {
if (cachePath == null || cachePath.size() < 1) return currentMap;
String cacheName = (String)cachePath.remove(0); // pull the first one
Object cacheObject = (Map<String,Object>)currentMap.get(cacheName);
if (cacheObject == null) {
cacheObject = new HashMap<String,Object>();
currentMap.put(cacheName,cacheObject);
}
if (! (cacheObject instanceof Map))
throw new IllegalArgumentException("Attempted to find a map at location ("+cachePath+") in cache ("+cacheName+"), but found a " + cacheObject.getClass().getName() + ".");
Map<String,Object> cache = (Map<String,Object>)cacheObject;
return _getLocationInMap(cache,cachePath);
}
}
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