Parsing the data to the App

After scripting the database through PHP, the next step would be to parse the data from the database to be viewable to the app. This can be through two main methods; either by parsing the data through XML, or else through JSON. Below I will be discussing the the pros and cons of both methods, and then give reasons why I chose to parse the data through JSON over XML.

XML Parsing

XML parsing in android is done using the DOM parser. The parser class mainly deals the following operations:

• Getting XML content by making HTTP request.
• Parsing XML content and getting DOM element of xml.
• Get each xml child element value by passing element node name.

The xml document is parsed by making http requests through Android code. A typical http request would be the following:

public String getXmlFromUrl(String url) {

String xml = null;

        try {

            // defaultHttpClient

            DefaultHttpClient httpClient = new DefaultHttpClient();

            HttpPost httpPost = new HttpPost(url);

            HttpResponse httpResponse = httpClient.execute(httpPost);

            HttpEntity httpEntity = httpResponse.getEntity();

            xml = EntityUtils.toString(httpEntity);

        } catch (UnsupportedEncodingException e) {

            e.printStackTrace();

        } catch (ClientProtocolException e) {

            e.printStackTrace();

        } catch (IOException e) {

            e.printStackTrace();

        }

        // return XML

        return xml;

}

After getting the XML content, the next would be to get the DOM element of the XML file. Finally the data elements need to be getting each xml child element value by passing element node name. The code in the app would then call the DOM file to update the data.

One of the main advantages of XML parsing is that it is visually more readable.

On the other hand, it is more difficult to code-wise to parse the data through xml.

JSON Parsing 

JSON is very light weight, structured, easy to parse and much human readable. JSON is best alternative to XML when the android app needs to interchange data and get information from the server. The following code will parse the data from the data with regards to the daily random quotations, from the following URL: http://tibi.scienceontheweb.net/qt_handler.php

{
 "Quote": [
 {
 "quoteID": "1",
 "quoteName": "For God so loved the world that he gave his one and only Son, that whoever believes in him shall not perish but have eternal life.",
 "quoteAuthor": "John 3:16"
 }
 ],
 "success": 1
}

The above is the data parsed from the Quote table in the database.

In general all the JSON nodes will start with a square bracket or with a curly bracket. The difference between [ and { is, the square bracket ([) represents starting of an JSONArray node whereas curly bracket ({) represents JSONObject. So while accessing these nodes we need to call appropriate method to access the data.

The following is the code for parsing the data using the JSONParser class in Android:

public JSONObject getJSONFromUrl(String url, List<NameValuePair> params) {
    try {
        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url);
        httpPost.setEntity(new UrlEncodedFormEntity(params));

        HttpResponse httpResponse = httpClient.execute(httpPost);
        HttpEntity httpEntity = httpResponse.getEntity();
        is = httpEntity.getContent();

    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    } catch (ClientProtocolException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        json = sb.toString();
        Log.e("JSON", json);
    } catch (Exception e) {
        Log.e("Buffer Error", "Error converting result " + e.toString());
    }

    // try parse the string to a JSON object
    try {
        jObj = new JSONObject(json);
    } catch (JSONException e) {
        Log.e("JSON Parser", "Error parsing data " + e.toString());
    }

    // return JSON String
    return jObj;
}

Finally, the app will show the data in the following doInBackground method:

protected String doInBackground(String... args) {
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    JSONObject json = jParser.getJSONFromUrl(url_quote_details,"GET", params);

    try {
        int success = json.getInt(CONNECTION_STATUS);

        if (success == 1) {
            Inspiration = json.getJSONArray(TABLE_QUOTE);
            for (int i = 0; i < Inspiration.length(); i++) {
                JSONObject insp = Inspiration.getJSONObject(i);

                name = insp.getString(COL_DESC);
                author = insp.getString(COL_AUTHOR);

                conCat = name + "_" + author;

            }
        } else {
            pDialog.dismiss();
        }
    } catch (JSONException e) {
        pDialog.dismiss();
        e.printStackTrace();
    }
    return conCat;
}

The app shows the data in the following method:

protected String doInBackground(String... args) {
    List<NameValuePair> params = new ArrayList<NameValuePair>();
    JSONObject json = jParser.getJSONFromUrl(url_quote_details,"GET", params);

    try {
        int success = json.getInt(CONNECTION_STATUS);

        if (success == 1) {
            Inspiration = json.getJSONArray(TABLE_QUOTE);
            for (int i = 0; i < Inspiration.length(); i++) {
                JSONObject insp = Inspiration.getJSONObject(i);

                name = insp.getString(COL_DESC);
                author = insp.getString(COL_AUTHOR);

                conCat = name + "_" + author;

            }
        } else {
            pDialog.dismiss();
        }
    } catch (JSONException e) {
        pDialog.dismiss();
        e.printStackTrace();
    }
    return conCat;
}

Below is how the parsed text would look in the App: