code: @Override
  	public synchronized Object putIfAbsent(Object key, Object value) {		
  		Cache cache = manager.getCache(ehcacheConf.getPredefinedCacheName());
  		if (!cache.isKeyInCache(key)){
  			Element element = new Element(key, value);
  			cache.put(element);
  		}
  		Element e = (Element)cache.get(key);
  		return e.getObjectValue();
  
  	}
docs: ehcache不支持putIfAbsent原子操作