cachemanager.java

一个非常好的FRAMWRK!是一个外国组织做的!不!

/**
 * Copyright 2003-2005 the original author or authors.
 * 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 com.jdon.controller.cache;

import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

import com.jdon.container.pico.Startable;
import com.jdon.util.Debug;

/**
  * Cacahe Managerment Pattern
  *
  * Client objects request objects from a CacheManager object by calling
  * its fetchObject method. The argument to the fetchObject method is an CacheKey object
  * that identifies the object to fetch. The fetchObject method works by first calling
  * the Cache object’s fetchObject method.
  *
  *

  *<br>
 * 本缓存工厂特点有两个：<br>
 * 1. 缓存的Key必须由本类产生<br>
 * 2. 本类的remove将自动清除与该Model相关的所有缓存对象。<br>
 *<br>
 * 凡是需要被缓存的对象，需要两步：<br>
 * 1. 在cacheTypes增加相应名称，<br>
 * 2. 提供获取该对象Key的名称<br>
 *
 *
 * @author banq
 */
public class CacheManager implements Startable {
  public  static String module = CacheManager.class.getName();

  
  private Cache cache;

  /** 将CacheKey和DataKey 对应关系保存起来
   *  可以根据DataKey寻找到不同的CacheKey
   *  可以清除DataKey有关的所有缓存
   *
   *  例如：1875 对应两种缓存：Model和Image，
   *  以1875为Key，可以清除它的所有缓存。
   *
   * */
  private Map cacheKeyMap;

  /**
   * 用于EJB容器
   * @return CacheFactory
   */
  public  CacheManager(Cache cache) {
    this.cache = cache;
    cacheKeyMap = Collections.synchronizedMap(new HashMap());
  }

  public void start() {
    Debug.logVerbose("CacheFactory start .....", module);
    clear();
  }

  public void stop() {
    clear();
    cache = null;
    cacheKeyMap = null;
  }

  public void clear() {
      if (cache != null)
        cache.clear();      
      if (cacheKeyMap != null)
        cacheKeyMap.clear();    
    }


  /**
   * 从缓存中获得缓存
   * @param cacheKey
   * @return
   */
  public Object fetchObject(StringKey key) {
    Debug.logVerbose("<-cache->try to get cache: " + key, module);
    Object o = cache.get(key.toString());
    if (o != null)
      Debug.logVerbose("<-cache->got it", module);
    return o;
  }

  /**
   * 保存到缓存中
   * @param cacheKey
   * @param value
   */
  public void putObect(StringKey key, Object value) {
    if (key == null) return;
   if (!cache.contain(key.toString())){
     cache.put(key.toString(), value);
     Debug.logVerbose("<-cache->save cache: " + key + ", size:" + cache.size(),
                      module);
   }
  }

  /**
   * 清除缓存
   * @param cacheKey
   */
  public  synchronized void removeObect(StringKey key) {
    cache.remove(key.toString());
    Debug.logVerbose("<-cache->remove the object of " + key + " from cache",
                     module);
  }

  /**
   * 清除缓存中该dataKey的相关所有缓存数据
   * 当该dataKey相关的数据增删改时，调用本方法。以便及时清除缓存。
   *
   * dataKey是数据的ID，如ProductId , ItemId等
   * @param dataKey
   * @param formName
   */
  public synchronized void removeCache(Object dataKey, CacheKeyFactory cacheKeyFactory) {
    if (dataKey == null)
      return;

    String cacheKeyStr = null;

    Iterator iter = cacheKeyFactory.getAllCacheKey(dataKey).iterator();
    while (iter.hasNext()) {
      cacheKeyStr = (String) iter.next();
      Debug.logVerbose("<-cache->remove cache:" + cacheKeyStr, module);
      removeObject(cacheKeyStr, cacheKeyFactory);
    }
  }

  private synchronized void removeObject(String cacheKeyStr, CacheKeyFactory cacheKeyFactory) {
    try {
      cache.remove(cacheKeyStr);
      cacheKeyFactory.removeCacheKey(cacheKeyStr);
    } catch (Exception e) {
      Debug.logError(" remove cache error:" + e + " cacheKey=" + cacheKeyStr,
                     module);
    }
  }

  public Map getCacheKeyMap() {
    return cacheKeyMap;
  }

  public void setCacheKeyMap(Map cacheKeyMap) {
    this.cacheKeyMap = cacheKeyMap;
  }

  public Cache getCache() {
    return cache;
  }

  public void setCache(Cache cache) {
    this.cache = cache;
  }

}