An Orkut Application via a JSON API

I talked about delegating rendering in Symfony for creating a JSON API. Now here’s a consumer: an Orkut opensocial gadget:


MobshareOrkutAPI = {

	api_url: 'http://api.mobshare/api.php',
	cache_time: 0, //0 to disable

	makeCachedRequest: function(url, callback, params, refreshInterval) {
	  var ts = new Date().getTime();
	  var sep = "?";
	  if (refreshInterval && refreshInterval > 0) {
	    ts = Math.floor(ts / (refreshInterval * 1000));
	  }
	  if (url.indexOf("?") > -1) {
	    sep = "&";
	  }
	  url = [ url, sep, "nocache=", ts ].join("");
	  gadgets.io.makeRequest(url, callback, params);
	},

	call: function(module, action, params, callback) {
		var options = {};
		options[gadgets.io.RequestParameters.CONTENT_TYPE] = gadgets.io.ContentType.JSON;
		this.makeCachedRequest(this.api_url + '/' + module + '/' + action + '?' + params, callback, options, this.cache_time);
	}

};

makeCachedRequest has been plaigarized from the Opensocial documentation and it’s very useful to bust the cache for requests. Also, notice this line for setting the content-type to JSON:


options[gadgets.io.RequestParameters.CONTENT_TYPE] = gadgets.io.ContentType.JSON;

This is how we access that API, a code fragment:


...
authenticate: function(alias, mobile_no, password) {
	MobshareOrkutAPI.call('user', 'authenticate',
		'alias=' + encodeURIComponent(alias) + '&mobile_no=' + encodeURIComponent(mobile_no) +
			'&password=' + encodeURIComponent(password),
 		MyOrkutApp.login
	);
}
...
login: function(orkut_response) {
	response = orkut_response.data;
	data_success = response['success'];
	data_error = response['error'];

	if(data_success) {
		html = '<h2>Login Successful!</h2>';
		html += '<p>Welcome: ' + data_success.name + '!</p>';
	} else if(data_error) {
		html = '<h2>Login Unsuccessful!</h2>';
		html += '<p>' + data_error + '!</p>';
	}

	document.getElementById('mobshare_login').innerHTML += html;
},
...

Note that orkut_response.data is automatically set by Orkut because you passed in the JSON content type; it parses the data received and creates a javascript object. Cool, ain’t it? It’s very easy to create a proper interactive Opensocial app this way.

Delegate Rendering in Symfony

Warning: pretty advanced Symfony ahead: if you’re not familiar with the framework, this wouldn’t make sense.

I recently developed a bare-bones API for Mobshare (it’s not yet live), and to keep everything clean, I abstracted away the rendering bit from the controller to an external class. It ended up being a sweet solution, so here it is!

I wanted this to be a JSONP API (the major use case would be a JS client, and parsing XML etc. via JS is a pain. Besides JSON is much shorter over the wire). I didn’t want to rewrite a lot of code: checking for a callback parameter and wrapping the returned string around the JSON output was just begging to be refactored away. So here it is, a generic Symfony JSON API wrapper class:


<?php

class JSONPAPI {

	const CALLBACK_PARAMETER = 'callback';

	var $status;
	var $data;
	var $callback;


	public function __construct($status, $data) {
		$this->status = $status;
		$this->data = $data;

		$callback_parameter_value = $this->getCurrentAction()->getRequestParameter(self::CALLBACK_PARAMETER);
		if($callback_parameter_value)
			$this->callback = $callback_parameter_value;
	}

	public function render() {
		$render_text = json_encode(array($this->status => $this->data));

		if($this->callback)
			$render_text = $this->callback . '(' . $render_text . ');';

		$this->setJavascriptHeaders();
		return $this->getCurrentAction()->renderText($render_text);
	}

	//hack to get the current action
	private function getCurrentAction() {
		return sfContext::getInstance()->getActionStack()->getLastEntry()->getActionInstance();
	}

	private function setJavascriptHeaders() {
		sfContext::getInstance()->getResponse()->setParameter('Content-Type', 'application/javascript', 'symfony/response/http/headers');
	}
}

The bits of magic here are the getCurrentAction() function and the render() call. It works on one very simple idea: everything in Symfony can be accessed from the sfContext::getInstance() object, you just need to dig deep enough.

Once you write this boiler-plate code, using it is very elegant. First, subclass it for your API:


<?php

require_once('JSONPAPI.class.php');

class MobshareAPI extends JSONPAPI {


}

And then, use it like so within your controller:


<?php
class userActions extends sfActions
{

	public function executeAuthenticate() {
		$valid_user = UserPeer::authenticate($this->getRequestParameter('alias'),
			$this->getRequestParameter('mobile_no'), $this->getRequestParameter('password'));
		if($valid_user instanceOf User) {
			$success = new MobshareAPI('success', $valid_user->toArray());
			return $success->render();
		} else {
			$error = new MobshareAPI('error', 'Authentication failed: Alias, mobile number or password invalid.');
			return $error->render();
		}
	}

}

Note: the rendering has been delegated to the $success and $error MobshareAPI objects. This allows for a really maintainable API. Adding functionality is much simpler since you don’t have to worry about the boilerplate.

You end up calling the API like this:


http://api.mobshare/user/authenticate?alias=vish&password=xxx&callback=handler

and you get back data which looks like this:


handler({"success":{"alias":"vish","name":"Vishnu Gopal","photo_mini": ...);

Note that callback handling is done entirely by the API and the controller needn’t worry about this parameter at all!

SlideShare Twitter Mashup

So here’s a SlideShare/Twitter Mashup (command-line ruby code) that does these things:

  1. Gets buzzwords from Twitter. It does this by analyzing tweets and getting popular words (filtering out common ones) with the Twitter API.
  2. Gets the most popular buzz word and searches the SlideShare tag database with it (using the SlideShare API).
  3. Prints out the buzzword and the slideshows that’s associated with it.

The source code might not be a great example of filtering and getting popular words, but it’s a good demo of how simple the Twitter and SlideShare APIs are (REST yay) and how easy Hpricot makes parsing XML docs.

There’s a zip (with the source code, common_words.txt, twitter_words.txt) here: slideshare_twitter.zip. Enjoy. 🙂