【代码】Android 传递数据使用gzip 清源教育安卓培训

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：
[java]

/**
* 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：
[java]

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：
[plain]
‹«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：
[java]

{"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：
[java]

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：
[java]

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：

[java]

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;
            */  
 
       }  
 
   } 

更多android技术问题欢迎加群探讨：314230976，验证码:csl,不写验证不予通过。