var jabox = new function Jabox() {
	var _units = {};
	var _products = {};
	
	/**
	 * Returns UnitEntity object with given id.
	 * If object does not exist, it returns null;
	 */
	this.getUnit = function(id) {
		if(id == null) {
			return null;
		}
		var data = _units[id.toString()];
		if(data == null) {
			this.onNonExistingEntity();
		}
		return data;
	};
	
	/**
	 * Adds unit to collection.
	 * 
	 * @param {UnitEntity} UnitEntity which has to be added to collection.
	 */
	this.addUnit = function(data) {
		_units[data.getId().toString()] = data;
	};

	/**
	 * Returns Product object with given id.
	 * If object does not exist, it returns null;
	 */
	this.getProduct = function(id) {
		if(id == null) {
			return null;
		}
		var data = _products[id.toString()];
		if(data == null) {
			this.onNonExistingEntity();
		}
		return data;
	};
	
	/**
	 * Adds product to collection.
	 * 
	 * @param {Product} Product which has to be added to collection.
	 */
	this.addProduct = function(data) {
		_products[data.getId().toString()] = data;
	};
	
	
	this.onNonExistingEntity = function() {
		alert('Ooops, entity does not exist.');
	};
};