Using Drupal menu system callback mapping to retrieve JSON or XML data

In my previous post I talked about Drupal menu system callback mapping. Today I'm going to show you how Drupal menu system callback mapping can be used to retrive JSON or XML data.

The way to accomplish the task is to register a path for a menu item with an optional argument. If you pass that optional argument along with the request URL callback function will return JSON data else it will return XML data. In that way callback function will serve both data formats.

Following is a coding example of above mentioned scenario.

<?php
//hook_perm implementation
function example_perm() {
    return array(
        'access city'
    );
}

//hook_menu implementation
function example_menu() {
    $items = array();
 
    //menu item 
    $items['full_city_list'] = array(
        'title' => t('City List JSON'
        ), 'page callback' => 'full_city_list', 'page arguments' => array(
            1
        ), 'access arguments' => array(
            'access city'
        ), 'type' => MENU_CALLBACK);   

    return $items;
}

function full_city_list() {
 $jsonParam=arg(1);//optional argument
 $result = db_query("SELECT  tid,name FROM term_data  WHERE  vid=2 order by name ASC");
 
 if(strcmp($jsonParam, "json") == 0){
    $response = array();
    
    while ($city_data = db_fetch_object($result)) {
        $response[$city_data->name]['city_name'] = $city_data->name;
        $response[$city_data->name]['tid'] = $city_data->tid;
    }

    if (!empty($response)) {
        //encodes city data as json  
        $jsonstrCityList = json_encode($response);
        echo $jsonstrCityList;
    } else {
        return false;
    }
 }elseif(strcmp($jsonParam, "") == 0){
 //sending city data as xml
 $dom = new DOMDocument("1.0");
    $root_elm = $dom->createElement("markers");
    $root = $dom->appendChild($root_elm);    

    while ($city_data = db_fetch_object($result)) {

        $marker_elm = $dom->createElement("marker");
        $marker_node = $root->appendChild($marker_elm);

        $marker_node->setAttribute("name", $city_data->name);
        $marker_node->setAttribute("tid", $city_data->tid);
    }
    header("Content-type: text/xml");
    echo $dom->saveXML();
 }
}
?>

output for http://example.com/full_city_list/json

{"Agalawatta":{"city_name":"Agalawatta","tid":"156"},"Ahungalla":{"city_name":"Ahungalla","tid":"214"},"Akurana":{"city_name":"Akurana","tid":"164"},"Akuressa":{"city_name":"Akuressa","tid":"162"},"Aluthgama":{"city_name":"Aluthgama","tid":"120"},"Ambalangoda":{"city_name":"Ambalangoda","tid":"125"},"Ampara":{"city_name":"Ampara","tid":"211"},"Anuradhapura":{"city_name":"Anuradhapura","tid":"46"},"Arugambay":{"city_name":"Arugambay","tid":"114"},"Avissawella":{"city_name":"Avissawella","tid":"212"},"Badulla":{"city_name":"Badulla","tid":"108"},"Balangoda":{"city_name":"Balangoda","tid":"149"},"Balapitiya":{"city_name":"Balapitiya","tid":"486"},"Bandarawela":{"city_name":"Bandarawela","tid":"197"}}

output for http://example.com/full_city_list

<markers>
<marker name="Agalawatta" tid="156"/>
<marker name="Ahungalla" tid="214"/>
<marker name="Akurana" tid="164"/>
<marker name="Akuressa" tid="162"/>
<marker name="Aluthgama" tid="120"/>
<marker name="Ambalangoda" tid="125"/>
<marker name="Ampara" tid="211"/>
<marker name="Anuradhapura" tid="46"/>
<marker name="Arugambay" tid="114"/>
<marker name="Avissawella" tid="212"/>
<marker name="Badulla" tid="108"/>
<marker name="Balangoda" tid="149"/>
<marker name="Balapitiya" tid="486"/>
<marker name="Bandarawela" tid="197"/>
</markers>

Parsing JSON (comes as a response to a web request) using java

JSON (JavaScript Object Notation) as in definition is a light weight data exchange format, a fat free alternative to XML. In today's post I will show you how to parse JSON (comes as a response to a web request) using java.

First download json-lib and add it to your classpath. You'll also have to add following libraries to your classpath

1. commons-lang.jar
2. commons-beanutils.jar
3. commons-collections.jar
4. commons-logging.jar
5. ezmorph.jar

What you need next is a request url and it's response should be JSON data. You will see mine in the example code I've provided, if you know how to use firebug the task will be much more simpler. In your browser run that request you'll get the JSON data which I parse, it's lengthy that's why I didn't add it in here. If you get untidy JSON data, format it using jasonlint.

Now let's move on to the example code, it's not hard to understand, simply go through it. Refer comments for clarifications.

java code

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import net.sf.json.JSONArray;
import net.sf.json.JSONObject;
import net.sf.json.JSONSerializer;

public class JsonParse { 

 public static void main(String[] args) {
  String jsonString = "";

  String city = "London";
  String country = "United+Kingdom";

  //This is the request url  
  String requestUrl = "http://www.bing.com/travel/hotel/hotelReferenceData.do?q="
    + city
    + "%2C+"
    + country
    + "+leave+07%2F08%2F2011+return+07%2F10%2F2011+adults%3A2+rooms%3A1&distanceFrom=22&HotelPriceRange=1%2C2%2C3%2C4&pageOffset=0&pageCount=240&cim=2011-07-08&com=2011-07-10&a=2&c=0&r=1&sortBy=PopularityDesc";
  try {
   URL url = new URL(requestUrl.toString());
   BufferedReader in = new BufferedReader(new InputStreamReader(
     url.openStream()));
   String inputLine;

   while ((inputLine = in.readLine()) != null) {
    //JSON data get stored as a string
    jsonString = inputLine;

   }
   in.close();
   //the way to parse JSON array
   JSONArray json = (JSONArray) JSONSerializer.toJSON(jsonString);
   //getting another JSON string to parse
   String parse1 = json.getString(0);
   
   //the way to parse JSON object
   JSONObject json2 = (JSONObject) JSONSerializer.toJSON(parse1);
   //getting a json array inside JSON object
   JSONArray array1 = json2.getJSONArray("hotels");

   for (int i = 0; i < array1.size(); i++) {
    //getting a JSON object inside JSON array
    JSONObject jhotelrec = array1.getJSONObject(i);    
    System.out.println("Hotel Name= "+jhotelrec.getString("name")+"\n"+"Geo Codes= "+jhotelrec.getJSONArray("geoPoint").getString(0)+","+jhotelrec.getJSONArray("geoPoint").getString(1));
    }

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

}