// $Header: /home/cvs/jakarta-jmeter/src/protocol/http/org/apache/jmeter/protocol/http/util/DOMPool.java,v 1.5 2004/02/12 00:29:49 sebb Exp $
/*
 * Copyright 2003-2004 The Apache Software Foundation.
 *
 * 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 org.apache.jmeter.protocol.http.util;

import java.util.HashMap;
import org.w3c.dom.Document;

/**
 * The purpose of this class is to cache the DOM Documents in memory and
 * by-pass parsing. For old systems or laptops, it's not practical to parse the
 * XML documents every time. Therefore using a memory cache can reduce the CPU
 * usage.
 * 

 * For now this is a simple version to test the feasibility of caching. If it
 * works, this class will be replaced with an Apache commons or something
 * equivalent. If I was familiar with Apache Commons Pool, I would probably
 * use it, but since I don't know the API, it is quicker for Proof of Concept
 * to just write a dumb one. If the number documents in the pool exceed several
 * hundred, it will take a long time for the lookup.
 * 

 * Created on:  Jun 17, 2003

 * 
 * @author Peter Lin
 * @version $Revision: 1.5 $
 */
public final class DOMPool
{
    /**
     * The cache is created with an initial size of 50. Running a webservice
     * test on an old system will likely run into memory or CPU problems long
     * before the HashMap is an issue.
     */
    protected static HashMap MEMCACHE = new HashMap(50);

    /**
     * Return a document.
     * @param key
     * @return Document
     */
    public static Document getDocument(Object key)
    {
        return (Document) MEMCACHE.get(key);
    }

    /**
     * Add an object to the cache.
     * @param key
     * @param data
     */
    public static void putDocument(Object key, Object data)
    {
        MEMCACHE.put(key, data);
    }
    
    /**
     * Private constructor to prevent instantiation.
     */
    private DOMPool()
    {
    }
}