public static Container getContainer(String containerName) throws WebConfigException{
		
		if(containerName == null){
			throw new WebConfigException("we can not find init-param named \"container\" in web.xml");
		}
		if(!supportThisTypeContainer(containerName)){
			throw new WebConfigException("container name is wrong or it is unsupported now!");
		}
		containerName = containerName.toLowerCase();
		String containerClassPath = ContainerFactory.class.getPackage().getName() + "." + 
				containerName.substring(0, 1).toUpperCase() + containerName.substring(1) + "Container";
		try {
			Object container = Class.forName(containerClassPath).newInstance();
			return (Container)container;
		} catch (InstantiationException e) {
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			logger.warn("the class: " + containerClassPath + " is not found!");
			e.printStackTrace();
		}
		return null;
	}