本程序采用JAVA所定，举个例子是模拟浏览器登录小米官网，采用的类主要是HttpURLConnection,HttpsURLConnectionURL请求的类别: 分二类,GET与POST请求。二者的区别在于：     

　 a:) get请求可以获取静态页面，也可以把参数放在URL字符串后面，传递给servlet， 
     b:) post与get的不同之处在于post的参数不是放在URL字串里面，而是放在http请求的正文内。 小米官网登录分析，浏览器首先打开此地址，进行第一次会话，https://account.xiaomi.com/pass/serviceLogin，会话的过程中会保存会话ID,以后每次请求都需要附上此ID才行，否则服务器会认为用户是重新登录，有了此ID，服务器会认为是同一个用户此次请求是GET请求，相应的HttpURLConnction的设置如下

url=new URL(urlStr);httpConn=(HttpURLConnection) url.openConnection();httpConn.setRequestMethod("GET");HttpsURLConnection.setFollowRedirects(false);httpConn.setRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; qdesk 2.4.1263.203; .NET4.0C; .NET4.0E; .NET CLR 2.0.50727");httpConn.setRequestProperty("Accept-Language","zh-cn");httpConn.setRequestProperty("Accept", "application/msword, application/xaml+xml, application/x-ms-xbap, application/x-ms-application, */*");httpConn.setRequestProperty("Accept-Encoding","gzip, deflate");httpConn.setUseCaches(false);httpConn.setRequestProperty("Host","account.xiaomi.com");httpConn.setRequestProperty("Connection", "Keep-Alive");httpConn.setConnectTimeout(15000);httpConn.setReadTimeout(20000);httpConn.setAllowUserInteraction(false);

设置完后，即发送请求：

httpConn.getInputStream();String cookieVal = null;String key=null;for (int i = 1; (key = httpConn.getHeaderFieldKey(i)) != null; i++ ) {System.out.println(key+"-----"+httpConn.getHeaderField(i));if (key.equalsIgnoreCase("set-cookie")){cookieVal = httpConn.getHeaderField(i);cookieVal = cookieVal.substring(0, cookieVal.indexOf(";"));System.out.println(cookieVal);String []str=sessionId.split(";");boolean flag=false;for(int t=0;t<str.length;t++){if(str[t]==cookieVal)flag=true;}if(!flag){sessionId=sessionId+cookieVal+";";}                        }}BufferedReader in = null;sessionId=sessionId.substring(0,sessionId.length()-1);InputStream inz=httpConn.getInputStream();in = new BufferedReader(new InputStreamReader(inz,"UTF-8"));String str=httpConn.getHeaderField("Content-Encoding");if(str!=null&&str.trim().endsWith("gzip")){GZIPInputStream gzin = new GZIPInputStream(inz);in = new BufferedReader(new InputStreamReader(gzin, "UTF-8"));}        String line="";while((line=in.readLine())!=null){System.out.println(line);}

上述代码会获取会话ID,JSESSION，注意服务器可能会返回gzip格式的数据，要进行相应的处理

有了会话ID后，即可进行登录,登录采用的是POST请求，POST请求参数是通过PrintWriter写入，从返回的数据中获得相应的cookie值作下一次使用

注意请求参数的设置，参数的设置可以查看页面源代码可知，Post请求需要传的参数为passToken,user,pwd,callback,sid,hidden

相应的HttpURLConnction的设置如下

url=new URL(urlStr);httpConn=(HttpsURLConnection) url.openConnection();httpConn.setRequestMethod("POST");HttpsURLConnection.setFollowRedirects(false);System.out.println("second:"+sessionId);httpConn.setRequestProperty("Cookie", sessionId);httpConn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");httpConn.setRequestProperty("Accept", "application/msword, application/xaml+xml, application/x-ms-xbap, application/x-ms-application, */*");httpConn.setRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; qdesk 2.4.1263.203; .NET4.0C; .NET4.0E; .NET CLR 2.0.50727");httpConn.setRequestProperty("Accept-Language","zh-cn");httpConn.setRequestProperty("Accept-Encoding", "gzip, deflate");httpConn.setRequestProperty("Connection", "Keep-Alive");httpConn.setRequestProperty("Host","account.xiaomi.com");httpConn.setRequestProperty("Content-Length",String.valueOf(param.getBytes()));httpConn.setRequestProperty("Referer","https://account.xiaomi.com/pass/serviceLogin");httpConn.setDoOutput(true);httpConn.setDoInput(true);httpConn.setConnectTimeout(15000);httpConn.setUseCaches(false);httpConn.setAllowUserInteraction(false);httpConn.setInstanceFollowRedirects(false);

获得数据并设置cookie为进一步访问做准备

PrintWriter out = new PrintWriter(httpConn.getOutputStream());out.print(param);out.flush();out.close();InputStream inz=httpConn.getInputStream();in = new BufferedReader(new InputStreamReader(inz,"UTF-8"));String key=null;String cookieVal = null;String str=httpConn.getHeaderField("Content-Encoding");if(str!=null&&str.trim().endsWith("gzip")){GZIPInputStream gzin = new GZIPInputStream(inz);in = new BufferedReader(new InputStreamReader(gzin, "UTF-8"));}for (int i = 1; (key = httpConn.getHeaderFieldKey(i)) != null; i++ ) {System.out.println(key+"-----"+httpConn.getHeaderField(i));if (key.equalsIgnoreCase("set-cookie")) {cookieVal = httpConn.getHeaderField(i);cookieVal = cookieVal.substring(0, cookieVal.indexOf(";"));if(cookieVal.indexOf("passToken")>-1){passToken=cookieVal.substring(cookieVal.indexOf("=")+1);}if(cookieVal.indexOf("userId")>-1){userId=cookieVal.substring(cookieVal.indexOf("=")+1);}}}String line;while ((line = in.readLine())!= null){System.out.println(line);}httpConn.getInputStream().close();

写到这了，你就可以看到登录成功后你自已的用户信息，随后的每一次访问都需要先前设置的cookie