HTTP協議上的GZIP編碼是一種用來改進WEB應用程序性能的技術。大流量的WEB站點常常使用GZIP壓縮技術來減少文件大小，減少文件大小有兩個明顯的好處，一是可以減少存儲空間，二是通過網絡傳輸文件時，可以減少傳輸的時間。作者在寫這篇博客時經過測試，4.4MB的文本數據經過Gzip傳輸到客戶端之後變為392KB，壓縮效率極高。
一.服務端
服務端有2種方式去壓縮，一種可以自己壓縮，但是更推薦第二種方式，用PrintWriter作為輸出流，工具類代碼如下
/**
* 判斷瀏覽器是否支持 gzip 壓縮
* @param req
* @return boolean 值
*/
public static boolean isGzipSupport(HttpServletRequest req) {
String headEncoding = req.getHeader("accept-encoding");
if (headEncoding == null || (headEncoding.indexOf("gzip") == -1)) { // 客戶端 不支持 gzip
return false;
} else { // 支持 gzip 壓縮
return true;
}
}
/**
* 創建 以 gzip 格式 輸出的 PrintWriter 對象，如果瀏覽器不支持 gzip 格式，則創建普通的 PrintWriter 對象，
* @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 壓縮
pw = new PrintWriter(new GZIPOutputStream(resp.getOutputStream()));
// 在 header 中設置返回類型為 gzip
resp.setHeader("content-encoding", "gzip");
} else { // // 客戶端 不支持 gzip
pw = resp.getWriter();
}
return pw;
}
servlet代碼如下：
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setCharacterEncoding("utf-8");
response.setHeader("Content-Encoding", "gzip");
String ret = "{\"ContentLayer\":{\"title\":\"內容層\"},\"PageLink\":{\"title\":\"頁面跳轉\"},\"WebBrowser\":{\"title\":\"瀏覽器\"},"
+ "\"InlinePage\":{\"title\":\"內嵌頁面\"},\"VideoComp\":{\"title\":\"視頻\"},"
+ "\"PopButton\":{\"title\":\"內容開關\"},\"ZoomingPic\":{\"title\":\"縮放大圖\"},"
+ "\"Rotate360\":{\"title\":\"360度旋轉\"}}";
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);
}
在代理軟件中跟蹤到的數據如下：
‹«VrÎÏ+IÍ+ñI¬L-R²ªV*É,ÉIU²R:rëÄÝM•ju”ÓS}2ó²‘e/m>üìÌë«@òá©INEùåŨúŸ¬?pàØw¼g^Nf^*ÈTóo™R–™’šïœŸ[€¬àÔåc[ÁÖç8•–”äç¡»nÿª7@
¢òós3óÒ2“‘Uœþºýè–Ïg&pide;€Tå—$–¤› +r·¸ðä‡Zh¤†ˆ
實際數據如下：
{"ContentLayer":{"title":"內容層"},"PageLink":{"title":"頁面跳轉"},"WebBrowser":{"title":"瀏覽器"},"InlinePage":{"title":"內嵌頁面"},"VideoComp":{"title":"視頻"},"PopButton":{"title":"內容開關"},"ZoomingPic":{"title":"縮放大圖"},"Rotate360":{"title":"360度旋轉"}}
二.Android客戶端
得到HttpClient代碼：
private static DefaultHttpClient getHttpClient() {
DefaultHttpClient httpClient = new DefaultHttpClient();
// 設置 連接超時時間
httpClient.getParams().setParameter(
HttpConnectionParams.CONNECTION_TIMEOUT, TIMEOUT_CONNECTION);
// 設置 讀數據超時時間
httpClient.getParams().setParameter(HttpConnectionParams.SO_TIMEOUT,
TIMEOUT_SOCKET);
// 設置 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);
// 設置 請求超時時間
httpPost.getParams().setParameter(HttpConnectionParams.SO_TIMEOUT,
TIMEOUT_SOCKET);
httpPost.setHeader("Connection", "Keep-Alive");
httpPost.addHeader("Accept-Encoding", "gzip");
return httpPost;
}
訪問網絡代碼：
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;
*/
}
}
