缓存机制实现（不通过框架实现）代码,Java代码库,德仔网

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【Java】缓存机制实现（不通过框架实现）
作者:磨砂轮 / 发布于2015/1/4/ 426

	import java.util.Collection;
	import java.util.Collections;
	import java.util.Iterator;
	import java.util.List;
	import java.util.Map;
	import java.util.concurrent.ConcurrentHashMap;
	
	import org.springframework.beans.factory.annotation.Autowired;
	import org.springframework.stereotype.Component;
	
	import net.blogjava.frankiegao123.log.slf4j.Log;
	import net.blogjava.frankiegao123.log.slf4j.LogFactory;
	
	/**
	* System.Config 配置缓存
	*
	* @author frankiegao123
	* 2010-6-10 下午02:48:35
	*/
	@Component("configCache")
	public class ConfigCache implements ConfigService {
	
	 private final static Log log = LogFactory.getLog(ConfigCache.class);
	
	 /**
	 * 更新缓存时记录的时间
	 */
	 private volatile long time = 0L;
	
	 /**
	 * 正在更新缓存时的门闩，为 true 时表示当前没有更新缓存，为 true 时表示当前正在更新缓存
	 */
	 private volatile boolean updateGate = true;
	
	 /**
	 * 缓存容器
	 */
	 private Map<String, SysConfig> cache = new ConcurrentHashMap<String, SysConfig>();
	
	 private CommonDao commonDao;
	
	 @Autowired
	 public ConfigCache(CommonDao commonDao) {
	 this.commonDao = commonDao;
	 log.info("initializing cache...");
	 refreshCache();
	 time = System.currentTimeMillis();
	 log.info("initialized cache finished, cache size: {}, set cache time to current: {}, cache timeout: {}ms", cache.size(), time, ConfigConstant.CACHE_TIMEOUT);
	 }
	
	 /**
	 * 根据配置的键名获取配置值
	 *
	 * @param configKey
	 * @return
	 * @author frankiegao123
	 * 2010-6-10 上午11:18:33
	 */
	 public SysConfig getSysConfig(String configKey) {
	 long current = System.currentTimeMillis();
	 if(updateGate && isTimeout(current)) {
	 synchronized (this) {
	 if(updateGate) {
	 timeoutSynRefresh(current);
	 }
	 }
	 }
	 return cache.get(configKey);
	 }
	
	 /**
	 * 超时时更新缓存。该方法需要在同步环境中调用
	 * @param current
	 * @author frankiegao123
	 * 2010-6-10 上午11:16:30
	 */
	 private void timeoutSynRefresh(long current) {
	 updateGate = false;
	 log.info("refresh cache start..., time out: {}, size: {}, set updateGate to false", (current - time) / 1000.0, cache.size());
	 try {
	 refreshCache();
	 time = current;
	 log.info("refresh cache finished, size after update: {}, set cache time to current: {}", cache.size(), String.valueOf(time));
	 } catch (Exception e) {
	 log.error("refresh cache failed", e);
	 } finally {
	 updateGate = true;
	 log.info("refresh cache finished, set updateGate to true");
	 }
	 }
	
	 /**
	 * 更新缓存数据
	 *
	 * @author frankiegao123
	 * 2010-6-10 上午11:15:55
	 */
	 private void refreshCache() {
	 List<SysConfig> configs = commonDao.getSysConfigs();
	 for(Iterator<SysConfig> i = configs.iterator(); i.hasNext(); ) {
	 SysConfig config = i.next();
	 cache.put(config.getKey(), config);
	 }
	 commonDao.clear();
	 SysConfig config = cache.get(SysConfig.TEST_KEY);
	 if(config == null) {
	 log.error("refresh cache, cannot find TEST_KEY");
	 } else {
	 log.info("refresh cache, find TEST_KEY = [{}]", config.getValue());
	 }
	 }
	
	 /**
	 * 缓存是否超时
	 *
	 * @param current
	 * @return
	 * @author frankiegao123
	 * 2010-6-10 上午11:16:12
	 */
	 private boolean isTimeout(long current) {
	 return (current - time >= ConfigConstant.CACHE_TIMEOUT);
	 }
	
	 Collection<SysConfig> getSysConfigs() {
	 return Collections.unmodifiableCollection(cache.values());
	 }
	
	 int getSize() {
	 return cache.size();
	 }
	
	 long getTime() {
	 return time;
	 }
	
	 boolean isUpdateGate() {
	 return updateGate;
	 }
	
	 void refresh() {
	 time = 0L;
	 log.info("refresh: reset cache time to 0");
	 getSysConfig("none");
	 log.info("refresh: refresh cache finished, cache: {0}", String.valueOf(time));
	 }
	}
试试其它关键字
　缓存　　缓存机制　
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