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Android

Posted by peter peter
peter peter
9,151 Points

how do i connect an android app to MongoDB on a remote server? how do i parse the JSON response?

I need pub/sub functionality; thereby updating my android app when new information becomes available. my server is privately hosted. the server stack entails express.js and mongoDB.

2 Answers

Chris Wolchesky
Chris Wolchesky
12,025 Points
Chris Wolchesky
Chris Wolchesky
12,025 Points

You'd have to create some sort of middle-ware API to interact with the database on behalf of your Android app. Express is great at this, alternatively I also like Restify (http://restify.com/) for creating a quick Node.js REST API. Within Android, you can interact with this API a couple of different ways. The easiest way is to use a library such as Retrofit (http://square.github.io/retrofit/) to essentially use your API as a Java Interface. Alternatively, you can use an AsyncTask (http://developer.android.com/reference/android/os/AsyncTask.html) to create a request to the API endpoint URL manually and load the resulting InputStream object into a JSONObject to retrieve the data. Here's a quick example of that at work using the Cat Facts API:

private class CatFactsActivity extends AsyncTask<Object, Void, JSONObject> {

    @Override
    protected JSONObject doInBackground(Object... params) {
        JSONObject jsonResponse = null;
        int responseCode;

        try {
            URL requestUrl = new URL("http://catfacts-api.appspot.com/api/facts");
            HttpURLConnection connection = (HttpURLConnection) requestUrl.openConnection();
            connection.setRequestProperty("Accept-Encoding", "identity");
            connection.connect();
            responseCode = connection.getResponseCode();
            if (responseCode != HttpURLConnection.HTTP_OK) {
                Log.e(TAG, "Status Code: " + responseCode);
            } else {
                InputStream stream = connection.getInputStream();
                Reader reader = new InputStreamReader(stream);
                int contentLength = connection.getContentLength();
                if (contentLength > 0) {
                    char[] buffer = new char[contentLength ];
                    reader.read(buffer);
                    Log.d(TAG, buffer);
                    jsonResponse = new JSONObject(String.valueOf(buffer));
                } else {
                    String jsonData = isToString(stream);
                    jsonResponse = new JSONObject(jsonData);
                }

                Log.d(TAG, jsonResponse.toString(2));
                connection.disconnect();
            }

        }
        catch (Exception e) {
            Log.e(TAG, "Exception: ", e);
        }


        return jsonResponse;
    }

    protected void onPostExecute(JSONObject data) {
        mFactJSON = data;
    }

    protected String isToString(InputStream is) {
        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
        int nRead;
        byte[] data = new byte[65536];

        try {
            while ((nRead = is.read(data, 0, data.length)) != -1) {
                buffer.write(data, 0, nRead);
            }

            buffer.flush();
        } catch (IOException e) {
            Log.e(TAG, "Exception caught: ", e);
        }

        return buffer.toString();
    }
}
peter peter
peter peter
9,151 Points
peter peter
peter peter
9,151 Points

brilliant. thanks, Chris. much appreciated.