GetResponseBodyAsStream()方法读取到的响应体流为中文乱码

        //1. 获取响应返回的信息
            //*猫的responseHeader的Content-Encoding=gzip，且Content-Type的charset=GBK
            //*东的responseHeaders里没有Content-Encoding，且Content-Type的charset=UTF-8
            GetMethod getMethod = new GetMethod(url);
            ...
            InputStream in = getMethod.getResponseBodyAsStream();
            BufferedReader reader = null;
            Header header = getMethod.getResponseHeader("Content-Encoding");
            if (header != null) {//天猫
                if ("gzip".equals(header.getValue())) {
                    GZIPInputStream gis = new GZIPInputStream(in);//使用GZIP包装一下
                    reader = new BufferedReader(new InputStreamReader(gis, "GBK"));
                }
            } else {//京东
                reader = new BufferedReader(new InputStreamReader(in, "UTF-8"));
            }
            StringBuffer buffer = new StringBuffer();
            String info = reader.readLine();
            while (info != null) {
                buffer.append(info);
                buffer.append("\n");
                info = reader.readLine();
            }
            responseStr = buffer.toString();