memcached高并发防止穿透db

//冲突延时 1秒 
private static final int MUTEX_EXP = 1;
 
//冲突键 
private static final String MUTEX_KEY_PREFIX = "MUTEX_";

 /** 
     * 冲突判定 
     * @param key 
     * @param exp 
     * @return true 冲突 
     */  
	private boolean isMutex(String key) {  
        boolean status = true;  
        try {  
            if (xmemcachedClient.add(MUTEX_KEY_PREFIX + key, MUTEX_EXP, "true")) {  
                status = false;  
            }  
        } catch (Exception e) {  
            logger.error(e.getMessage(), e);  
        }  
        return status;  
    }


	private List<RecommendDataView> getRecommendDataViewList(String key, int rid, int pageNum, int pageSize) {
		List<RecommendDataView> recommendDataViewList  = null;
		recommendDataViewList = getCache(key);
		if (recommendDataViewList == null) {
			if (!isMutex(key)) {
				recommendDataViewList = recommendDataService.getRecommendDataViewList(rid, pageNum, pageSize);
				if (recommendDataViewList != null) {
					cache(key, recommendDataViewList);
				}
				removeMutex(key);
			} else {
				while(true) {
				    try {
				    	int interval = 0;
						Thread.sleep(50);
						recommendDataViewList = (List<RecommendDataView>)getCache(key);
						interval++;
						if (interval > 5 || recommendDataViewList != null) {
							break;
						}
					} catch (InterruptedException e) {
						logger.info(e.getMessage(), e);
					}
				}
			}
		} 
	
		return recommendDataViewList;
	}