java- how to use gson library to parse a json response+ storing session id so that it can be accessed by javascript functions in gae

Question

I am trying to authenticate to a server's secure URL using java.net.urlconnection - based on the useful tutorial at Using java.net.URLConnection to fire and handle HTTP requests

The response will be as given below--

Return: A session id object: {'session_id': 'username:session_token'} This session_id will be used for all methods which require authentication.

This response is JSON response, and I am thinking of using the Google GSON library (since my web app is on Google App Engine).

The code I have used so far (based on the tutorial to which I have given link above) is given below--

        String url = "https://api.wordstream.com/authentication/login";
        String charset = "UTF-8";
        String param1 = WORDSTREAM_API_USERNAME;
        String param2 = WORDSTREAM_API_PASSWORD;
        // ...
        String query = String.format("username=%s&password=%s", 
         URLEncoder.encode(param1, charset), 
         URLEncoder.encode(param2, charset));
        URLConnection connection = new URL(url + "?" + query).openConnection();
        connection.setRequestProperty("Accept-Charset", charset);
        InputStream response = connection.getInputStream();
        InputStream error = ((HttpURLConnection) connection).getErrorStream();
        //now checking HTTP Response status
        int status = ((HttpURLConnection) connection).getResponseCode();

How do I proceed further to obtain the JSON response and retrieve session ID from that response correctly?

Another question- I want to store the session ID in session data that can be accessed by javascript functions, because I plan to use javascript functions to make calls and obtain further data. Is this possible, and how to implement this?

score 0 · Accepted Answer · answered Oct 28 '11 at 22:50

Step 1- Create a subclass- declare it as static so that it can be utilised by the GSON library. This subclass should mimic the data contained in a single JSON Response- in our case only the session ID is stored in the response- hence this class contains just one string variable...

 static class LR { 

  public String response; 

  public LR() {
  // No args constructor for LR
   }
 }

Now, use BUfferedReader and readline to read the entire response and store it in a string variable.

InputStream response = connection.getInputStream();
        BufferedReader br = new BufferedReader(new     
InputStreamReader(response));
String str="", temp;
while (null != ((temp = br.readLine())))
{
    System.out.println (str);
    str=str + temp;             
}

Finally, invoke 'fromJSON(string, class)' to obtain the value-

Gson gson = new Gson();
LR obj2 = gson.fromJson(str, LR.class);   
return(" Session ID="+ obj2.response);

java- how to use gson library to parse a json response+ storing session id so that it can be accessed by javascript functions in gae

1 Answers1