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:
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/**
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* 判断浏览器是否支持 gzip 压缩
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* @param req
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* @return boolean 值
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*/
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public static boolean isGzipSupport(HttpServletRequest req) {
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String headEncoding = req.getHeader("accept-encoding");
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if (headEncoding == null || (headEncoding.indexOf("gzip")
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== -1)) { // 客户端 不支持 gzip
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return false;
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} else { // 支持 gzip 压缩
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return true;
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}
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}
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/**
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* 创建 以 gzip 格式 输出的 PrintWriter 对象,如果浏览器不支持
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gzip 格式,则创建普通的 PrintWriter 对象,
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* @param req
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* @param resp
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* @return
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* @throws IOException
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*/
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public static PrintWriter createGzipPw(HttpServletRequest req,
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HttpServletResponse resp) throws IOException {
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PrintWriter pw = null;
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if (isGzipSupport(req)) { // 支持 gzip 压缩
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pw = new PrintWriter(new GZIPOutputStream
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(resp.getOutputStream()));
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// 在 header 中设置返回类型为 gzip
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resp.setHeader("content-encoding", "gzip");
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} else { // // 客户端 不支持 gzip
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pw = resp.getWriter();
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}
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return pw;
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}
servlet代码如下:
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public void doPost(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException {
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response.setCharacterEncoding("utf-8");
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response.setHeader("Content-Encoding", "gzip");
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String ret = "{\"ContentLayer\":{\"title\":\"内容层\"},
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\"PageLink\":{\"title\":\"页面跳转\"},\"WebBrowser\":{\"title\":\
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"浏览器\"},"
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+ "\"InlinePage\":{\"title\":\"内嵌页面\"},\"VideoComp
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\":{\"title\":\"视频\"},"
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+ "\"PopButton\":{\"title\":\"内容开关\"},\"ZoomingPic
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\":{\"title\":\"缩放大图\"},"
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+ "\"Rotate360\":{\"title\":\"360度旋转\"}}";
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PrintWriter pw = new PrintWriter(new GZIPOutputStream
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(response.getOutputStream()));
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pw.write(ret);
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pw.close();
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}
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public void doGet(HttpServletRequest request, HttpServletResponse
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response)
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throws ServletException, IOException {
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this.doPost(request, response);
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}
在代理软件中跟踪到的数据如下:
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‹«VrÎÏ+IÍ+ñI¬L-R²ªV*É,ÉIU²R:rëÄÝM•ju”ÓS}2ó²‘e/m>üìÌë«@òá©INEùåŨúŸ¬?
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pàØw¼g^Nf^*ÈTóo™R–™’šïœŸ[€¬àÔåc[ÁÖç8•–”äç¡»nÿª7@
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¢òós3óÒ2“‘Uœþºýè–Ïg÷€Tå—$–¤› +r·¸ðä‡Zh¤†ˆ
实际数据如下:
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{"ContentLayer":{"title":"内容层"},"PageLink":{"title":"页面跳转"},
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"WebBrowser":{"title":"浏览器"},"InlinePage":{"title":"内嵌页面"},
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"VideoComp":{"title":"视频"},"PopButton":{"title":"内容开关"},
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"ZoomingPic":{"title":"缩放大图"},"Rotate360":{"title":"360度旋转"
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}}
二.Android客户端
得到HttpClient代码:
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private static DefaultHttpClient getHttpClient() {
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DefaultHttpClient httpClient = new DefaultHttpClient();
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// 设置 连接超时时间
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httpClient.getParams().setParameter(
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HttpConnectionParams.CONNECTION_TIMEOUT, TIMEOUT_
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CONNECTION);
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// 设置 读数据超时时间
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httpClient.getParams().setParameter(HttpConnectionParams.
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SO_TIMEOUT,
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TIMEOUT_SOCKET);
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// 设置 字符集
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httpClient.getParams().setParameter("http.protocol.
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content-charset",
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UTF_8);
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return httpClient;
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}
得到HttpPost:
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private static HttpPost getHttpPost(String url) {
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HttpPost httpPost = new HttpPost(url);
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// 设置 请求超时时间
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httpPost.getParams().setParameter(HttpConnectionParams.SO_
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TIMEOUT,
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TIMEOUT_SOCKET);
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httpPost.setHeader("Connection", "Keep-Alive");
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httpPost.addHeader("Accept-Encoding", "gzip");
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return httpPost;
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}
访问网络代码:
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public static InputStream http_post_return_byte(String url,
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Map<String, String> params) throws AppException {
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DefaultHttpClient httpclient = null;
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HttpPost post = null;
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HttpResponse response = null;
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StringBuilder sb = null;
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StringEntity stringEntity = null;
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try {
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httpclient = getHttpClient();
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post = getHttpPost(url);
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sb = new StringBuilder();
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if (params != null && !params.isEmpty()) {
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Logger.d("In http_post the url is get here");
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for (Entry<String, String> entry : params.
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entrySet()) {
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sb.append(entry.getKey())
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.append("=")
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.append(URLEncoder.encode(entry.
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getValue(),
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HTTP.UTF_8)).append("&");
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}
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sb.deleteCharAt(sb.lastIndexOf("&"));
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Logger.d("In http_post the url is " + url + " and
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params is "
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+ sb.toString());
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stringEntity = new StringEntity(sb.toString());
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stringEntity
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.setContentType
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("application/x-www-form-urlencoded");
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post.setEntity(stringEntity);
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}
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response = httpclient.execute(post);
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int statusCode = response.getStatusLine().
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getStatusCode();
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Logger.d("statusCode is " + statusCode);
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if (statusCode != HttpStatus.SC_OK) {
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throw AppException.http(statusCode);
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}
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InputStream is = response.getEntity().getContent();
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Header contentEncoding = response
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.getFirstHeader("Content-Encoding");
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if (contentEncoding != null
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&& contentEncoding.getValue().
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equalsIgnoreCase("gzip")) {
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is = new GZIPInputStream(new BufferedInputStream
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(is));
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}
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return is;
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} catch (ClientProtocolException e) {
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e.printStackTrace();
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throw AppException.http(e);
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} catch (IOException e) {
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e.printStackTrace();
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throw AppException.network(e);
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} finally {
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/*
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* if (!post.isAborted()) {
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*
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* post.abort(); } httpclient = null;
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*/
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}
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}