Android中使用gzip传递数据

HTTP协议上的GZIP编码是一种用来改进WEB应用程序性能的技术。大流量的WEB站点常常使用GZIP压缩技术来减少文件大小，减少文件大小有两个明显的好处，一是可以减少存储空间，二是通过网络传输文件时，可以减少传输的时间。作者在写这篇博客时经过测试，4.4MB的文本数据经过Gzip传输到客户端之后变为392KB，压缩效率极高。

 

一.服务端

服务端有2种方式去压缩，一种可以自己压缩，但是更推荐第二种方式，用PrintWriter作为输出流，工具类代码如下

 

/**
         * 判断浏览器是否支持 gzip 压缩
         * @param req
         * @return boolean 值
         */
        public static boolean isGzipSupport(HttpServletRequest req) {
            String headEncoding = req.getHeader("accept-encoding");
            if (headEncoding == null || (headEncoding.indexOf("gzip") == -1)) { // 客户端 不支持 gzip
                return false;
            } else { // 支持 gzip 压缩
                return true;
            }
        }

        /**
         * 创建 以 gzip 格式 输出的 PrintWriter 对象，如果浏览器不支持 gzip 格式，则创建普通的 PrintWriter 对象，
         * @param req
         * @param resp
         * @return
         * @throws IOException
         */
        public static PrintWriter createGzipPw(HttpServletRequest req, HttpServletResponse resp) throws IOException {
            PrintWriter pw = null;
            if (isGzipSupport(req)) { // 支持 gzip 压缩
                pw = new PrintWriter(new GZIPOutputStream(resp.getOutputStream()));
                // 在 header 中设置返回类型为 gzip
                resp.setHeader("content-encoding", "gzip");
            } else { // // 客户端 不支持 gzip
                pw = resp.getWriter();
            }
            return pw;
        }

 

servlet代码如下：

 public void doPost(HttpServletRequest request, HttpServletResponse response)
         throws ServletException, IOException {
     response.setCharacterEncoding("utf-8");
     response.setHeader("Content-Encoding", "gzip");
     String ret = "{"ContentLayer":{"title":"内容层"},"PageLink":{"title":"页面跳转"},"WebBrowser":{"title":"浏览器"},"
             + ""InlinePage":{"title":"内嵌页面"},"VideoComp":{"title":"视频"},"
             + ""PopButton":{"title":"内容开关"},"ZoomingPic":{"title":"缩放大图"},"
             + ""Rotate360":{"title":"360度旋转"}}";

     PrintWriter pw = new PrintWriter(new GZIPOutputStream(response.getOutputStream()));
     pw.write(ret);
     pw.close();
 }

 public void doGet(HttpServletRequest request, HttpServletResponse response)
         throws ServletException, IOException {
     this.doPost(request, response);
 }

在代理软件中跟踪到的数据如下：

  ‹«VrÎÏ+IÍ+ñI¬L-R²ªV*É,ÉIU²R:rëÄÝM•ju”ÓS}2ó²‘e/m>üì̏ë«@òá©INEùåŨúŸ¬?pàØw¼g^Nf^*ÈTóo™R–™’šïœŸ[€¬àÔåc[ÁÖç8•–”äç¡»nÿª7@
 ¢òós3óÒ2“‘Uœþºýè–Ïg÷€Tå—$–¤› +r·¸ðä‡Zh¤†ˆ

实际数据如下：

 

 

 {"ContentLayer":{"title":"内容层"},"PageLink":{"title":"页面跳转"},"WebBrowser":{"title":"浏览器"},"InlinePage":{"title":"内嵌页面"},"VideoComp":{"title":"视频"},"PopButton":{"title":"内容开关"},"ZoomingPic":{"title":"缩放大图"},"Rotate360":{"title":"360度旋转"}}

 

二.Android客户端

 

得到HttpClient代码：

 private static DefaultHttpClient getHttpClient() {
         DefaultHttpClient httpClient = new DefaultHttpClient();

         // 设置 连接超时时间
         httpClient.getParams().setParameter(
                 HttpConnectionParams.CONNECTION_TIMEOUT, TIMEOUT_CONNECTION);
         // 设置 读数据超时时间
         httpClient.getParams().setParameter(HttpConnectionParams.SO_TIMEOUT,
                 TIMEOUT_SOCKET);
         // 设置 字符集
         httpClient.getParams().setParameter("http.protocol.content-charset",
                 UTF_8);
         return httpClient;
     }

得到HttpPost：

 

 private static HttpPost getHttpPost(String url) {
         HttpPost httpPost = new HttpPost(url);
         // 设置 请求超时时间
         httpPost.getParams().setParameter(HttpConnectionParams.SO_TIMEOUT,
                 TIMEOUT_SOCKET);
         httpPost.setHeader("Connection", "Keep-Alive");
         httpPost.addHeader("Accept-Encoding", "gzip");
         return httpPost;
     }

访问网络代码：

 

 

 public static InputStream http_post_return_byte(String url,
             Map<String, String> params) throws AppException {
         DefaultHttpClient httpclient = null;
         HttpPost post = null;
         HttpResponse response = null;
         StringBuilder sb = null;
         StringEntity stringEntity = null;
         try {
             httpclient = getHttpClient();
             post = getHttpPost(url);
             sb = new StringBuilder();
             if (params != null && !params.isEmpty()) {
                 Logger.d("In http_post the url is get here");
                 for (Entry<String, String> entry : params.entrySet()) {
                     sb.append(entry.getKey())
                             .append("=")
                             .append(URLEncoder.encode(entry.getValue(),
                                     HTTP.UTF_8)).append("&");
                 }
                 sb.deleteCharAt(sb.lastIndexOf("&"));
                 Logger.d("In http_post the url is " + url + " and params is "
                         + sb.toString());
                 stringEntity = new StringEntity(sb.toString());
                 stringEntity
                         .setContentType("application/x-www-form-urlencoded");
                 post.setEntity(stringEntity);
             }

             response = httpclient.execute(post);
             int statusCode = response.getStatusLine().getStatusCode();
             Logger.d("statusCode is " + statusCode);
             if (statusCode != HttpStatus.SC_OK) {
                 throw AppException.http(statusCode);
             }

             InputStream is = response.getEntity().getContent();

             Header contentEncoding = response
                     .getFirstHeader("Content-Encoding");
             if (contentEncoding != null
                     && contentEncoding.getValue().equalsIgnoreCase("gzip")) {
                 is = new GZIPInputStream(new BufferedInputStream(is));
             }
             return is;

         } catch (ClientProtocolException e) {
             e.printStackTrace();
             throw AppException.http(e);
         } catch (IOException e) {
             e.printStackTrace();
             throw AppException.network(e);
         } finally {

             /*
              * if (!post.isAborted()) {
              *
              * post.abort(); } httpclient = null;
              */

         }

     }