base.MemCache Maven / Gradle / Ivy

Show more of this group Show more artifacts with this name
Show all versions of base Show documentation

A collection of basic java utility classes that provide basic features for a standalone/simple JEE application. Backed by a Cassandra, MySQL, or SQLite database, it provides, web page templates, user and group management, and a searchable online audit log of all user activity.

There is a newer version: 1.5.4

Show newest version

/*
 This is free and unencumbered software released into the public domain.

 Anyone is free to copy, modify, publish, use, compile, sell, or
 distribute this software, either in source code form or as a compiled
 binary, for any purpose, commercial or non-commercial, and by any
 means.

 In jurisdictions that recognize copyright laws, the author or authors
 of this software dedicate any and all copyright interest in the
 software to the public domain. We make this dedication for the benefit
 of the public at large and to the detriment of our heirs and
 successors. We intend this dedication to be an overt act of
 relinquishment in perpetuity of all present and future rights to this
 software under copyright law.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
 OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 OTHER DEALINGS IN THE SOFTWARE.
 */
package base;

import java.util.Date;
import java.util.Hashtable;
import java.util.LinkedList;
import java.util.Map;
import java.util.NoSuchElementException;

public class MemCache {

	private LinkedList expiryQueue = new LinkedList();
	private Map items = new Hashtable();
	private int timeout;

	private int hits = 0;
	private int misses = 0;

	/**
	 * How long to hold an object cached in memory, in seconds.
	 */
	public MemCache(int timeout) {
		this.timeout = timeout;
	}

	public void addItem(Object object, String hash) {
		MemCacheItem i = new MemCacheItem(object, hash, (new Date()).getTime() + timeout*1000);
		expiryQueue.addLast(i);
		items.put(hash, i);
	}

	public void flushItem(String hash) {
		expireAgedObjects();
		items.remove(hash);
	}

	public Object getItem(String hash) {
		expireAgedObjects();
		MemCacheItem i = items.get(hash);
		if(i == null) {
			misses++;
			return null;
		} else {
			hits++;
			return i.object;
		}
	}

	private void expireAgedObjects() {
		long now = (new Date()).getTime();
		MemCacheItem i;

		try {
			while((i = expiryQueue.getFirst()) != null) {
				if(i.expiry > now) {
					break;
				}
				items.remove(i.hash);
				expiryQueue.removeFirst();
			}
		} catch(NoSuchElementException e) {
		}

	}

	public int getMisses() {
		return misses;
	}

	public int getHits() {
		return hits;
	}

	public void flush() {
		items.clear();
		expiryQueue.clear();
	}

	private class MemCacheItem {

		public long expiry;
		public String hash;
		public Object object;

		public MemCacheItem(Object object, String hash, long expiry) {
			this.expiry = expiry;
			this.hash = hash;
			this.object = object;
		}

	}

}