Base64解码，编码

//解码
List<CartItem> cart = null;
		
		Cookie[] cookies = request.getCookies();
		boolean flag = true;
		for (Cookie cookie : cookies) {
			if(EGO_CART_COOKIE.equals(cookie.getName())){
				String value = cookie.getValue();
				Decoder decoder = Base64.getDecoder();
				byte[] decode = decoder.decode(value);
				String jsonString = new String(decode);
				cart = JsonUtils.jsonToList(jsonString, CartItem.class);
				flag = false;
				break;
			}
		}


//加入cookie之前，Base64编码
			String json = JsonUtils.objectToJson(cart);
			Encoder encoder = Base64.getEncoder();
			String encodeToString = encoder.encodeToString(json.getBytes()); 
			Cookie c = new Cookie(EGO_CART_COOKIE, encodeToString);
			
			//暴露cookie，所有人可以访问
			//这种方式不安全，我们需要通过domain属性来设置一个域名保护
			c.setPath("/");
			
			response.addCookie(c);