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base4j分布式缓存（基于j2cache）
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/**
 *  Copyright 2014-2015 Oschina
 *
 *  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.base4j.j2cache.ehcache;

import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.base4j.j2cache.CacheException;
import com.base4j.j2cache.CacheExpiredListener;
import com.base4j.j2cache.CacheProvider;
import net.sf.ehcache.CacheManager;

/**
 * EhCache Provider plugin
 * 
 * Taken from EhCache 1.3 distribution
 * @author liudong
 * @author wendal
 */
public class EhCacheProvider implements CacheProvider {

	private final static Logger log = LoggerFactory.getLogger(EhCacheProvider.class);
	public static String KEY_EHCACHE_NAME = "ehcache.name";
	public static String KEY_EHCACHE_CONFIG_XML = "ehcache.configXml";

	private CacheManager manager;
	private ConcurrentHashMap _CacheManager ;

	@Override
	public String name() {
		return "ehcache";
	}

    /**
     * Builds a Cache.
     * Even though this method provides properties, they are not used.
     * Properties for EHCache are specified in the ehcache.xml file.
     * Configuration will be read from ehcache.xml for a cache declaration
     * where the name attribute matches the name parameter in this builder.
     *
     * @param name the name of the cache. Must match a cache configured in ehcache.xml
     * @param autoCreate auto create cache region ?
     * @param listener cache listener
     * @return a newly built cache will be built and initialised
     * @throws CacheException inter alia, if a cache of the same name already exists
     */
    public EhCache buildCache(String name, boolean autoCreate, CacheExpiredListener listener) throws CacheException {
    	EhCache ehcache = _CacheManager.get(name);
    	if(ehcache == null && autoCreate){
		    try {
	            synchronized(_CacheManager){
	            	ehcache = _CacheManager.get(name);
	            	if(ehcache == null){
			            net.sf.ehcache.Cache cache = manager.getCache(name);
			            if (cache == null) {
			                log.warn("Could not find configuration [" + name + "]; using defaults.");
			                manager.addCache(name);
			                cache = manager.getCache(name);
			                log.debug("started EHCache region: " + name);                
			            }
			            ehcache = new EhCache(cache, listener);
			            _CacheManager.put(name, ehcache);
	            	}
	            }
		    }
	        catch (net.sf.ehcache.CacheException e) {
	            throw new CacheException(e);
	        }
    	}
        return ehcache;
    }

	/**
	 * Callback to perform any necessary initialization of the underlying cache implementation
	 * during SessionFactory construction.
	 *
	 * @param props current configuration settings.
	 */
	public void start(Properties props) throws CacheException {
		if (manager != null) {
            log.warn("Attempt to restart an already started EhCacheProvider.");
            return;
        }
		
		// 如果指定了名称,那么尝试获取已有实例
		String ehcacheName = (String)props.get(KEY_EHCACHE_NAME);
		if (ehcacheName != null && ehcacheName.trim().length() > 0)
			manager = CacheManager.getCacheManager(ehcacheName);
		if (manager == null) {
			// 指定了配置文件路径? 加载之
			if (props.containsKey(KEY_EHCACHE_CONFIG_XML)) {
				manager = new CacheManager(props.getProperty(KEY_EHCACHE_CONFIG_XML));
			} else {
				// 加载默认实例
				manager = CacheManager.getInstance();
			}
		}
        _CacheManager = new ConcurrentHashMap();
	}

	/**
	 * Callback to perform any necessary cleanup of the underlying cache implementation.
	 */
	public void stop() {
		if (manager != null) {
            manager.shutdown();
            _CacheManager.clear();
            manager = null;
        }
	}

}