JSON Parsing

JSON Parsing

JSON is JavaScript Object Notation. JSON parsing is the most comfort and straightforward method to parse responses from web services. It is also a better option other than the xml parsing method.

A sample example that parses the data from a web server; http://api.androidhive.info/contacts/ is given below. This program fetches and parses only name and email data from the web.

JSONParsingExample.class

package php.sql;

import java.io.BufferedReader;

import java.io.InputStream;

import java.io.InputStreamReader;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.client.HttpClient;

import org.apache.http.client.methods.HttpPost;

import org.apache.http.impl.client.DefaultHttpClient;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

import android.app.Activity;

import android.app.AlertDialog;

import android.content.DialogInterface;

import android.content.DialogInterface.OnClickListener;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

public class JSONParsingExample  extends Activity

{

          InputStream is;

          String result = "";

          String data = "";

    /** Called when the activity is first created. */

    @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

    }

    public void click(View v)

    {

        //http post

        try{

                HttpClient httpclient = new DefaultHttpClient();

                HttpPost httppost = new HttpPost("http://api.androidhive.info/contacts/");

                //httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));

                HttpResponse response = httpclient.execute(httppost);

                HttpEntity entity = response.getEntity();

                is = entity.getContent();

        }catch(Exception e){

                Log.e("log_tag", "Error in http connection "+e.toString());

        }

       

        //convert response to string

        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();

          

                result=sb.toString();

        }catch(Exception e){

                Log.e("log_tag", "Error converting result "+e.toString());

        }

         

        //parse json data

        try{

     

         

          JSONObject jObj = new JSONObject(result);

          JSONArray jArray =jObj.getJSONArray("contacts");

              //JSONArray jArray = new JSONArray(result);

               

                for(int i=0;i<jArray.length();i++){

                        JSONObject json_data = jArray.getJSONObject(i);

                     

                        String std=json_data.getString("name");

                        String place=json_data.getString("email");

                     

                        data=data+"\n"+std+"  "+place;

                        Log.i("log_tag",result);

                       

                }

        }

       

        catch(JSONException e)

        {

                Log.e("log_tag", "Error parsing data "+e.toString());

        }

        new AlertDialog.Builder(this).setPositiveButton("Ok",new OnClickListener() {

            //@Override

            public void onClick(DialogInterface dialog, int which)

            {

            }

    }).setMessage(data).setTitle("Student Details").create().show();

    }

}

main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical" >

    <Button android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Generate Result"

        android:layout_marginTop="40dp"

        android:layout_gravity="center"

       

        android:onClick="click"/>

</LinearLayout>

XML Parsing

AndroidXmlParsingActivity.class

package com.androidhive.xmlparsing;

import java.util.ArrayList;

import java.util.HashMap;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.w3c.dom.NodeList;

import android.app.ListActivity;

import android.content.Intent;

import android.os.Bundle;

import android.view.View;

import android.widget.AdapterView;

import android.widget.AdapterView.OnItemClickListener;

import android.widget.ListAdapter;

import android.widget.ListView;

import android.widget.SimpleAdapter;

import android.widget.TextView;

public class AndroidXMLParsingActivity extends ListActivity {

          // All static variables

          static final String URL = "http://api.androidhive.info/pizza/?format=xml";

          // XML node keys

          static final String KEY_ITEM = "item"; // parent node

          static final String KEY_ID = "id";

          static final String KEY_NAME = "name";

          static final String KEY_COST = "cost";

          static final String KEY_DESC = "description";

          @Override

          public void onCreate(Bundle savedInstanceState) {

                   super.onCreate(savedInstanceState);

                   setContentView(R.layout.main);

                   ArrayList<HashMap<String, String>> menuItems = new ArrayList<HashMap<String, String>>();

                   XMLParser parser = new XMLParser();

                   String xml = parser.getXmlFromUrl(URL); // getting XML

                   Document doc = parser.getDomElement(xml); // getting DOM element

                   NodeList nl = doc.getElementsByTagName(KEY_ITEM);

                   // looping through all item nodes <item>

                   for (int i = 0; i < nl.getLength(); i++) {

                             // creating new HashMap

                             HashMap<String, String> map = new HashMap<String, String>();

                             Element e = (Element) nl.item(i);

                             // adding each child node to HashMap key => value

                             map.put(KEY_ID, parser.getValue(e, KEY_ID));

                             map.put(KEY_NAME, parser.getValue(e, KEY_NAME));

                             map.put(KEY_COST, "Rs." + parser.getValue(e, KEY_COST));

                             map.put(KEY_DESC, parser.getValue(e, KEY_DESC));

                             // adding HashList to ArrayList

                             menuItems.add(map);

                   }

                   // Adding menuItems to ListView

                   ListAdapter adapter = new SimpleAdapter(this, menuItems,

                                      R.layout.list_item,

                                      new String[] { KEY_NAME, KEY_DESC, KEY_COST }, new int[] {

                                                          R.id.name, R.id.desciption, R.id.cost });

                   setListAdapter(adapter);

                   // selecting single ListView item

                   ListView lv = getListView();

                   lv.setOnItemClickListener(new OnItemClickListener() {

                             @Override

                             public void onItemClick(AdapterView<?> parent, View view,

                                                int position, long id) {

                                      // getting values from selected ListItem

                                      String name = ((TextView) view.findViewById(R.id.name)).getText().toString();

                                      String cost = ((TextView) view.findViewById(R.id.cost)).getText().toString();

                                      String description = ((TextView) view.findViewById(R.id.desciption)).getText().toString();

                                     

                                      // Starting new intent

                                      Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);

                                      in.putExtra(KEY_NAME, name);

                                      in.putExtra(KEY_COST, cost);

                                      in.putExtra(KEY_DESC, description);

                                      startActivity(in);

                             }

                   });

          }

}

XMLParser.class

package com.androidhive.xmlparsing;

import java.io.IOException;

import java.io.StringReader;

import java.io.UnsupportedEncodingException;

import javax.xml.parsers.DocumentBuilder;

import javax.xml.parsers.DocumentBuilderFactory;

import javax.xml.parsers.ParserConfigurationException;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.client.ClientProtocolException;

import org.apache.http.client.methods.HttpPost;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.util.EntityUtils;

import org.w3c.dom.Document;

import org.w3c.dom.Element;

import org.w3c.dom.Node;

import org.w3c.dom.NodeList;

import org.xml.sax.InputSource;

import org.xml.sax.SAXException;

import android.util.Log;

public class XMLParser {

          // constructor

          public XMLParser() {

          }

          /**

           * Getting XML from URL making HTTP request

           * @param url string

           * */

          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;

          }

         

          /**

           * Getting XML DOM element

           * @param XML string

           * */

          public Document getDomElement(String xml){

                   Document doc = null;

                   DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

                   try {

                             DocumentBuilder db = dbf.newDocumentBuilder();

                             InputSource is = new InputSource();

                           is.setCharacterStream(new StringReader(xml));

                           doc = db.parse(is);

                             } catch (ParserConfigurationException e) {

                                      Log.e("Error: ", e.getMessage());

                                      return null;

                             } catch (SAXException e) {

                                      Log.e("Error: ", e.getMessage());

                      return null;

                             } catch (IOException e) {

                                      Log.e("Error: ", e.getMessage());

                                      return null;

                             }

                  return doc;

          }

         

          /** Getting node value

            * @param elem element

            */

           public final String getElementValue( Node elem ) {

               Node child;

               if( elem != null){

                   if (elem.hasChildNodes()){

                       for( child = elem.getFirstChild(); child != null; child = child.getNextSibling() ){

                           if( child.getNodeType() == Node.TEXT_NODE  ){

                               return child.getNodeValue();

                           }

                       }

                   }

               }

               return "";

           }

           

           /**

            * Getting node value

            * @param Element node

            * @param key string

            * */

           public String getValue(Element item, String str) {           

                             NodeList n = item.getElementsByTagName(str);              

                             return this.getElementValue(n.item(0));

                   }

}

SingleMenuItemActivity.class

package com.androidhive.xmlparsing;

import android.app.Activity;

import android.content.Intent;

import android.os.Bundle;

import android.widget.TextView;

public class SingleMenuItemActivity  extends Activity {

         

          // XML node keys

          static final String KEY_NAME = "name";

          static final String KEY_COST = "cost";

          static final String KEY_DESC = "description";

          @Override

    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.single_list_item);

       

        // getting intent data

        Intent in = getIntent();

       

        // Get XML values from previous intent

        String name = in.getStringExtra(KEY_NAME);

        String cost = in.getStringExtra(KEY_COST);

        String description = in.getStringExtra(KEY_DESC);

       

        // Displaying all values on the screen

        TextView lblName = (TextView) findViewById(R.id.name_label);

        TextView lblCost = (TextView) findViewById(R.id.cost_label);

        TextView lblDesc = (TextView) findViewById(R.id.description_label);

        

        lblName.setText(name);

        lblCost.setText(cost);

        lblDesc.setText(description);

    }

}

main.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="fill_parent"

    android:orientation="vertical">

          <!-- Main ListView

                    Always give id value as list(@android:id/list)

          -->

    <ListView

        android:id="@android:id/list"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"/>

</LinearLayout>

list_item.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="fill_parent"

    android:layout_height="wrap_content"

    android:orientation="horizontal"> 

    <LinearLayout

        xmlns:android="http://schemas.android.com/apk/res/android"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:orientation="vertical">

                   <!-- Name Label -->

        <TextView

            android:id="@+id/name"

            android:layout_width="fill_parent"

            android:layout_height="wrap_content"

            android:textColor="#dc6800"

            android:textSize="16sp"

            android:textStyle="bold"

            android:paddingTop="6dip"

            android:paddingBottom="2dip" />

                   <!-- Description label -->

        <TextView

            android:id="@+id/desciption"

            android:layout_width="fill_parent"

            android:layout_height="wrap_content"

            android:textColor="#acacac"

            android:paddingBottom="2dip">

        </TextView>

        <!-- Linear layout for cost and price Cost: Rs.100 -->

        <LinearLayout

        xmlns:android="http://schemas.android.com/apk/res/android"

        android:layout_width="fill_parent"

        android:layout_height="wrap_content"

        android:orientation="horizontal">

        <!-- Cost Label -->

        <TextView

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:textColor="#5d5d5d"

            android:gravity="left"

            android:textStyle="bold"

            android:text="Cost: " >

        </TextView>

        <!-- Price Label -->

        <TextView

            android:id="@+id/cost"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:textColor="#acacac"

            android:textStyle="bold"

            android:gravity="left">

        </TextView>

        </LinearLayout>

    </LinearLayout>

</LinearLayout>

single_list_item.xml

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout

  xmlns:android="http://schemas.android.com/apk/res/android"

  android:orientation="vertical"

  android:layout_width="match_parent"

  android:layout_height="match_parent">

  <!-- Name Label -->

  <TextView android:id="@+id/name_label"

            android:layout_width="fill_parent"

            android:layout_height="wrap_content"

            android:textSize="25dip"

            android:textStyle="bold"

            android:paddingTop="10dip"

            android:paddingBottom="10dip"

            android:textColor="#dc6800"/>

  <!-- Description Label -->

  <TextView android:id="@+id/description_label"

            android:layout_width="fill_parent"

            android:layout_height="wrap_content"

            android:textColor="#acacac"/>

  <!-- Price Label -->

  <TextView android:id="@+id/cost_label"

                   android:layout_width="fill_parent"

                   android:layout_height="wrap_content"

                   android:textStyle="bold"/>

</LinearLayout>