sudo apt-get install nginx

使用Google登入

@Override
 protected void doGet(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
   
  // Google取得access_token的url
  URL urlObtainToken =  new URL("https://accounts.google.com/o/oauth2/token");
  HttpURLConnection connectionObtainToken =  (HttpURLConnection) urlObtainToken.openConnection();
    
  // 設定此connection使用POST
  connectionObtainToken.setRequestMethod("POST");
  connectionObtainToken.setDoOutput(true);
   
  // 開始傳送參數 
  OutputStreamWriter writer  = new OutputStreamWriter(connectionObtainToken.getOutputStream());
  writer.write("code="+req.getParameter("code")+"&");   // 取得Google回傳的參數code
  writer.write("client_id=xxxxxxxxxxxxxxxxxx&xxxx&");   // 這裡請將xxxx替換成自己的client_id
  writer.write("client_secret=xxxxxxxxxxxxxxxxxxx&");   // 這裡請將xxxx替換成自己的client_serect
  writer.write("redirect_uri=xxxxxxxxxxxxxxxxxxxx&");   // 這裡請將xxxx替換成自己的redirect_uri
  writer.write("grant_type=authorization_code");  
  writer.close();
  
  // 如果認證成功
  if (connectionObtainToken.getResponseCode() == HttpURLConnection.HTTP_OK){
   StringBuilder sbLines   = new StringBuilder("");
   
   // 取得Google回傳的資料(JSON格式)
   BufferedReader reader = 
       new BufferedReader(new InputStreamReader(connectionObtainToken.getInputStream(),"utf-8"));
   String strLine = "";
   while((strLine=reader.readLine())!=null){
    sbLines.append(strLine);
   }
  
   try {
       // 把上面取回來的資料，放進JSONObject中，以方便我們直接存取到想要的參數
    JSONObject jo = new JSONObject(sbLines.toString());
    
    // 印出Google回傳的access token
    resp.getWriter().println(jo.getString("access_token")); 
   } catch (JSONException e) {
    e.printStackTrace();
   }
  }
 }

URL urUserInfo =   
     new URL("https://www.googleapis.com/oauth2/v1/userinfo?access_token="+jo.getString("access_token")); 
 HttpURLConnection connObtainUserInfo =  (HttpURLConnection) urUserInfo.openConnection();
  
  
 //如果認證成功
 if (connObtainUserInfo.getResponseCode() == HttpURLConnection.HTTP_OK){
  StringBuilder sbLines   = new StringBuilder("");
   
  // 取得Google回傳的資料(JSON格式)
  BufferedReader reader = 
   new BufferedReader(new InputStreamReader(connObtainUserInfo.getInputStream(),"utf-8"));
  String strLine = "";
  while((strLine=reader.readLine())!=null){
   sbLines.append(strLine);
  }
  
  try {
   // 把上面取回來的資料，放進JSONObject中，以方便我們直接存取到想要的參數
   JSONObject jo = new JSONObject(sbLines.toString());
    
   // 印出Google回傳的"emailtoken
   resp.getWriter().println(jo.getString("email")); 
    
  } catch (JSONException e) {
   e.printStackTrace();
  }
 }