facebook real time update in java example

问题:

I'm working on a project which uses Facebook Graph Api to collect information about the public posts. There is a need to update this data Real-Time when changes come to this posts. i have seen a real time update mechanism using call back url https://developers.facebook.com/docs/graph-api/reference/app/subscriptions/ and https://developers.facebook.com/docs/graph-api/real-time-updates/ .. But i didnt get any idea of doing this in java. Please somebody help me using an example.

回答1:

Real time updates are available for page and user objects.Both of them requires the access token of the respective page or user.(For page you can check it using me/accounts or get it via giving page access permissions to your app).

Step 1: You will need a public ip where facebook will post the updates. Step 2: You need to setup your fb app to initiate real-time updates setup

  String appId = //your app id
  String token = //app token appId|appSecret
  String callbackUrl = //your public url
  PostMethod method = new PostMethod();
  method.setURI(new URI("https://graph.facebook.com/" + appId +
           "/subscriptions?callback_url=" + callbackUrl +
         "&object=page&fields=feed&verify_token=streamInit&method=POST&access_token="+
           token, false));

  HttpClient httpClient = new HttpClient();
  if (method != null) {
        int statusCode = httpClient.executeMethod(method);
        String response = new String(method.getResponseBody());
        if (statusCode == HttpStatus.SC_OK) {

                 //Completed streaming initiation
        }else{
           //Streaming initialization failed"
        }
     }
  } catch (Exception e) {

  }

Step 3:This will trigger facebook callback url validation.It can be a servlet or any other which will process the updates posted to callback url.Facebook will provide a challenge code in a get request which you need to resend.

 protected void doGet(HttpServletRequest request, HttpServletResponse response)
  throws ServletException, IOException {
  Map parametersMap = request.getParameterMap();
  if (parametersMap.size() > 0) {
     if (request.getParameter("hub.mode").equals("streamInit")) {
        System.out.println("Verify Token: " + request.getParameter("hub.verify_token"));
        System.out.println("Challenge number:" + request.getParameter("hub.challenge"));

        String responseToClient = request.getParameter("hub.challenge");
        response.setStatus(HttpServletResponse.SC_OK);
        response.getWriter().write(responseToClient);
        response.getWriter().flush();
        response.getWriter().close();

           //"Completed streaming setup on your url" 
     }
  } 

}

Step 3: Add your application as a page tab to subscribe from real time updates from that page.you will need a page Access token

  String appId = //your application id
  String pageId=//page id to subscribe from
  PostMethod method =
        new PostMethod("https://graph.facebook.com/" + pageId + "/tabs?app_id=" + appId +
              "&method=POST&access_token=" + pageToken);
  HttpClient httpClient = new HttpClient();
  try {
     int statusCode = httpClient.executeMethod(method);
     String response = new String(method.getResponseBody());
     if (statusCode == HttpStatus.SC_OK) {

        // "Completed tab addition"
     }else{
        // "Tab adding failed"
     }

  } catch (Exception e) {
     //"Tab adding failed" 
  }

Step 4 : Facebook will post updates via post request to your call back url.