This is the Apex Class of GoogleUrlShortener,which it shortener the Url's

GoogleUrlShortener.cls

/** 
  * This class exposes methods
  * that calls the google URL
  * shortener API to Shorten long
  * URL's
  * 
  * @author     Pavan Vempati
  * @since      22/02/2016
  * @version    1.0
  */
global class GoogleUrlShortener {
    /**
      * This Method calls the URL shortener 
      * API with the encoded key
      * grabs the Shortened URL from the Response.
      * 
      * @param      longURL  accepts the long URL that needs to be shorened
      * @since      22/02/2016
    */
    webService static void  shortenURL( String longURL, String bookmarkId ) {
        /**
          * Fetching the Encoded Key 
          * and the google URL shortener Endpoint
          * from the encoded key
          * by using custom setting
        */
        String encKey   = Google_API_Setting__c.getInstance( 'URL Shortener Key' ).Value__c;
        
        String endPoint = Google_API_Setting__c.getInstance( 'URL Shortener Endpoint'  ).Value__c;
        endPoint        = endPoint.replace( '{YOUR_API_KEY}',encKey );
        
        String  body    = '{"longUrl" : "' + longURL+ '"}';

        Http http             = new Http();
        HttpRequest httpReq   = new HttpRequest();
        HttpResponse httpResp = new HttpResponse();
        
        httpReq.setBody( body );
        httpReq.setMethod( 'POST' );
        httpReq.setHeader( 'Content-Type', 'application/json' );
        httpReq.setEndpoint( endPoint );
        
        httpResp = http.send( httpReq );
        
        JSONParser parser = JSON.createParser( HttpResp.getBody() );
        parser.nextToken();
        parser.nextToken();
        parser.nextToken();
        parser.nextValue();
        
        String sURL     =  parser.getText();
        
        Bookmark__c bm  = new Bookmark__c();
        bm.Id           = bookmarkId;
        bm.Short_URL__c = sURL;
        UPDATE bm;
    }
}