easycache.java

EasyDBO是一个超轻量级对象-关系映射（Object/Relation Mapping

package com.easyjf.cache;

import com.easyjf.cache.store.*;

import org.apache.log4j.*;

/**
 * Easy
 */
import java.util.*;
/**
 * 
 * <p>
 * Title: EasyCache核心引擎
 * </p>
 * 
 * <p>
 * Description: EasyCache实现ICache接口，提供具体的Cache功能
 * </p>
 * 
 * <p>
 * Copyright: Copyright (c) 2006
 * </p>
 * 
 * <p>
 * Company:EasyJF开源团队-EasyDBO项目组
 * </p>
 * 
 * @author 大峡
 * @version 1.0
 */
public class EasyCache implements ICache, Cloneable {
	public static final String DEFAULT_CACHE_NAME = "default";

	private final static Logger logger = Logger.getLogger(EasyCache.class);

	private static final int DEFAULT_STORE_POLICY = StorePolicy.LRU;

	private static final int DEFAULT_MAX_ELEMENTS = 100;

	private static final long DEFAULT_EXPIRY_SECONDS = 120;

	private static final String NULL_KEY="EASYDBOCACHE";
	// ~--- fields -------------------------------------------------------------

	private final long expiredInterval; // 超时间隔，秒

	private int hitCount; // 命中次数

	private final int maxElements; // 最大元素

	private int missCountNotFound; // 查找失败次数

	private String name; // 缓存名称

	private int status; // 状态

	private Store store; // 缓存数据存诸

	private int storePolicy; // 存储策略

	// ~--- constructors -------------------------------------------------------

	public EasyCache() {
		this(DEFAULT_CACHE_NAME, DEFAULT_STORE_POLICY, DEFAULT_MAX_ELEMENTS,
				DEFAULT_EXPIRY_SECONDS * 1000);
	}

	/**
	 * 
	 * @param name
	 *            String
	 * @param storePolicy
	 *            int
	 * @param maxElements
	 *            int
	 * @param expiredInterval
	 *            long
	 */
	public EasyCache(String name, int storePolicy, int maxElements,
			long expiredInterval) {
		this.storePolicy = storePolicy;
		this.maxElements = maxElements;
		this.expiredInterval = expiredInterval * 1000 ;
		this.name = name;
		this.store = MemoryStore.create(this);
	}

	// ~--- methods ------------------------------------------------------------

	/**
	 * 清除缓存中所有元素，但保留缓存在可用状态
	 * 
	 * @throws CacheException
	 *             缓存异常
	 */
	public void clear() throws CacheException {
		try {
			store.removeAll();
		} catch (Exception e) {
			throw new CacheException(e);
		}
	}

	/**
	 * 
	 * @return Object
	 * @throws CloneNotSupportedException
	 */
	public Object clone() throws CloneNotSupportedException {
		return super.clone();
	}

	/**
	 * 清除缓存，并使之不可用
	 * 
	 * @throws CacheException
	 *             缓存异常
	 */
	public void destroy() throws CacheException {
		try {
			store.dispose();
			// CacheManager.getInstance().removeCache(this.name);
		} catch (Exception e) {
			throw new CacheException(e);
		}
	}

	/**
	 * 未实现方法 Calls to this method should perform there own synchronization. It
	 * is provided for distributed caches. Because EHCache is not distributed
	 * this method does nothing.
	 * 
	 * @param key
	 *            元素键值
	 * @throws CacheException
	 *             缓存异常
	 */
	public void lock(Object key) throws CacheException {

		// TODO Auto-generated method stub
	}

	/**
	 * 放置对象到缓存中
	 * 
	 * @param key
	 *            可序列化的键值
	 * @param value
	 *            可序列化的元素值
	 * @throws CacheException
	 *             如果参数不可序列化，CacheManager停止或者出现其他异常
	 */
	public void put(Object key, Object value) throws CacheException {
		try {
			Element element = new Element(key, value);
			store.put(element);
		} catch (Exception e) {
			throw new CacheException(e);
		}
	}

	/**
	 * 清除匹配键值的元素值
	 * <p>
	 * 如果没有元素匹配，则没有清除动作且不抛出任何异常
	 * 
	 * @param key
	 *            需要清除的元素键值
	 * @throws CacheException
	 *             缓存异常
	 */
	public void remove(Object key) throws CacheException {
		try {
			store.remove(key);
		} catch (Exception e) {
			throw new CacheException(e);
		}
	}

	public void removeElement(Object value) {
		try {			
			store.removeElement(new Element(NULL_KEY,value));			
		} catch (Exception e) {			
			logger.error("从缓存中删除无素出现错误:" + e);
		}
	}

	/**
	 * 未实现方法 Calls to this method should perform there own synchronization. It
	 * is provided for distributed caches. Because EHCache is not distributed
	 * this method does nothing.
	 * 
	 * @param key
	 *            元素键值
	 * @throws CacheException
	 *             缓存异常
	 */
	public void unlock(Object key) throws CacheException {
		// TODO Auto-generated method stub
	}

	// ~--- get methods --------------------------------------------------------

	/**
	 * 获得匹配指定键值的元素值
	 * 
	 * @param key
	 *            返回元素的键值
	 * @return 之前放入缓存的元素值，如果找不到或者过期则为null
	 * @throws CacheException
	 *             缓存异常
	 */
	public Object get(Object key) throws CacheException {
		try {
			if (key == null) {
				return null;
			} else {
				Element element = store.get(key);
				
				if (element == null) {
					logger.debug("缓存元素 for " + key + " is null");
					missCountNotFound++;
					return null;
				} else {
					hitCount++;

					return element.getValue();
				}
			}
		} catch (Exception e) {
			throw new CacheException(e);
		}
	}

	/**
	 * 获得内存容纳元素的最大数量
	 * 
	 * @return 内存容纳元素的最大数量
	 */
	public int getElementCount() {

		// TODO Auto-generated method stub
		return store.getSize();
	}

	/**
	 * 
	 * @return long
	 */
	public long getExpiredInterval() {
		return expiredInterval;
	}

	/**
	 * 
	 * @return Set
	 */
	public Set getKeySet() {

		// TODO Auto-generated method stub
		return store.getKeySet();
	}

	/**
	 * 
	 * @return int
	 */
	public int getMaxElemnetCount() {

		// TODO Auto-generated method stub
		return this.maxElements;
	}

	/**
	 * 
	 * @return String
	 */
	public String getName() {

		// TODO Auto-generated method stub
		return this.name;
	}

	/**
	 * 获得内存中元素数量
	 * 
	 * @return 内存中元素数量，如果不明异常返回-1
	 */
	public long getSize() {
		try {
			return store.getSize();
		} catch (Throwable t) {
			return -1;
		}
	}

	/**
	 * 
	 * @return int
	 */
	public int getStatus() {
		return status;
	}

	/**
	 * 
	 * @return int
	 */
	public int getStorePolicy() {

		// TODO Auto-generated method stub
		return this.storePolicy;
	}

	/**
	 * 
	 * @param e
	 *            Element
	 * @return boolean
	 */
	public boolean isExpired(Element e) {	     
		return (System.currentTimeMillis() -(e.getLastAccessTime()==0?e.getCreationTime():e.getLastAccessTime())) > expiredInterval;
	}

	// ~--- set methods --------------------------------------------------------

	public void setName(String name) {
		this.name = name;
	}

	
	public void setStorePolicy(int storePolicy) {
		// TODO Auto-generated method stub
		this.storePolicy=storePolicy;
	}
	
}