/*
* #!
* Ontopia Engine
* #-
* Copyright (C) 2001 - 2013 The Ontopia Project
* #-
* Licensed 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 net.ontopia.utils;
import java.util.HashMap;
import java.util.Map;
/**
* INTERNAL: Grabber that maintains a cache of previously grabbed
* objects. It works with any implementation of GrabberIF.</p>
*
* The cache is first checked to see if a grabbed version already
* exists. Otherwise the object is grabbed and the cache is
* updated.</p>
*
* If the underlying grabber is modified or replaced, the cache is not
* refreshed automatically. This has to be done explicitly.</p>
*/
public class CachedGrabber<O, G> implements GrabberIF<O, G>, CachedIF {
protected GrabberIF<O, G> grabber;
protected Map<O, G> cache = new HashMap<O, G>();
public CachedGrabber(GrabberIF<O, G> grabber) {
this.grabber = grabber;
}
/**
* Gets the grabber that is being cached.
*/
public GrabberIF<O, G> getGrabber() {
return grabber;
}
/**
* Sets the grabber that is to be cached. Note that the cache is not
* refreshed. If the cache is to be cleared call the refresh()
* method explicitly.
*/
public void setGrabber(GrabberIF<O, G> grabber) {
this.grabber = grabber;
}
public G grab(O object) {
if (object == null) return null;
if (cache.containsKey(object)) return cache.get(object);
G grabbed = grabber.grab(object);
cache.put(object, grabbed);
return grabbed;
}
public void refresh() {
cache.clear();
}
}