cachedlistcontentrequest.java

jxta-cms-src-2.4.zip 是官网上的比较稳定的CMS源代码。目前是最稳定的高版本。

/*
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights
 * reserved.
 *
 * 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. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED 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 APACHE SOFTWARE FOUNDATION OR
 * ITS 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.
 *
 *====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 *
 * $Id: CachedListContentRequest.java,v 1.6 2006/02/07 20:43:50 bondolo Exp $
 *
 */

package net.jxta.share.client;

import java.util.Hashtable;
import java.util.Vector;
import net.jxta.share.ContentAdvertisement;
import net.jxta.peergroup.PeerGroup;
import net.jxta.share.CMS;

import org.apache.log4j.Logger;
import org.apache.log4j.Level;

/**
 * This class implements List Content Request.
 * It request a list of content from the given CMS request pipe.
 */

public class CachedListContentRequest extends ListContentRequest implements Runnable {

    private final static transient Logger LOG = Logger.getLogger(CachedListContentRequest.class.getName());

    private Cache cache = null;
    private static Hashtable cacheList = new Hashtable();

    public CachedListContentRequest(PeerGroup group, String inSubStr) {
        super(group, inSubStr);

        cache = (Cache)cacheList.get(CMS.getGroupId(group));
        if (cache == null) {
            cache = new Cache();
            cacheList.put(CMS.getGroupId(group), cache);
        }
        // The rest moved in routine below: a bad idea to start working
        // before the derived classes had a chance to finish constructing.
    }

    public void run() {
        if (cache != null) {
            cache.searchCache(this);

            // call the notify routine
            notifyMoreResults();
        }
    }

    protected synchronized void addResult(ContentAdvertisement cAdv) {
        // insert the result into the cache
        if (cache != null) {
            cache.add(cAdv);
        }

        super.addResult(cAdv);
    }

    class Cache {
        private static final long DEFAULT_LIFETIME = 10 * 60 * 1000L; // 10 minutes
        private Vector entries = null;

        public Cache() {
            entries = new Vector();
        }

        public synchronized void add(ContentAdvertisement cAdv) {
            if (LOG.isEnabledFor(Level.DEBUG))
                LOG.debug("Cache.add() "+System.currentTimeMillis()+" "+ cAdv.toString());

            // calculate the lifetime
            long lifeTime = System.currentTimeMillis() + DEFAULT_LIFETIME;

            // insert the result into the cache
            int i = 0;
            CacheEntry temp = null;
            for (; i < entries.size(); i++) {
                // get the entry
                temp = (CacheEntry)entries.elementAt(i);

                if (temp.equals(cAdv)) {
                    // reset the expiration time
                    if (LOG.isEnabledFor(Level.DEBUG))
                        LOG.debug("reset expire time" + temp.toString());
                    temp.expireTime = lifeTime;
                    break;
                }
            }

            if (i >= entries.size()) {
                // add the new element
                temp = new CacheEntry(cAdv, lifeTime);
                if (LOG.isEnabledFor(Level.DEBUG))
                    LOG.debug("add new entry to cache" + temp.toString());
                entries.addElement(temp);
            }

        }

        public synchronized void searchCache(ListContentRequest request) {
            // current time
            long currentTime = System.currentTimeMillis();

            if (LOG.isEnabledFor(Level.DEBUG))
                LOG.debug("Cache.searchCache() "+currentTime+" "+ request.getSubString());

            // check the cache for matches
            int i = 0;
            while (i < entries.size()) {
                // get the entry
                CacheEntry temp = (CacheEntry)entries.elementAt(i);

                // check if this element has expired
                if (currentTime > temp.expireTime) {
                    if (LOG.isEnabledFor(Level.DEBUG))
                        LOG.debug("Cache.searchCache() entry expired "+temp.toString());
                    entries.removeElementAt(i);
                    continue;
                }


                // check if the advertisement matches the query
                if (isMatch(temp.cAdv, request.getSubString())) {
                    request.addResult(temp.cAdv);
                }

                // advance to the next entry
                i++;
            }
        }

        private boolean isMatch(ContentAdvertisement cadv, String subString) {
            if (subString == null) {
                return true;
            }

            // check if the name contains the substring
            String name = cadv.getName();
            if (name != null) {
                name = name.toLowerCase();
                if (name.indexOf(subString) != -1) {
                    return true;
                }
            }

            // check if the description contains the substring
            String desc = cadv.getDescription();
            if (desc != null) {
                desc = desc.toLowerCase();
                if (desc.indexOf(subString) != -1) {
                    return true;
                }
            }

            return false;
        }

        class CacheEntry {
            public ContentAdvertisement cAdv = null;
            public long expireTime = 0;

            protected CacheEntry(ContentAdvertisement cAdv, long expireTime) {
                this.cAdv = cAdv;
                this.expireTime = expireTime;
            }

            protected boolean equals(ContentAdvertisement adv) {
                if (cAdv != null) {
                    return cAdv.equals(adv);
                }
                return false;
            }

            public String toString() {
                String str = " expireTime "+expireTime+" ";
                if (cAdv != null) {
                    str = str + cAdv.toString();
                }
                return str;
            }
        }
    }
}