angularJS factory中包含xhr时，通过promise获取结果

angular.module('shopping', []).
  factory('shoppingData',function($http, $q){
    return{
      apiPath:'/api/shoppingCart/',
      getAllItems: function(){
        //Creating a deferred object
        var deferred = $q.defer();

        //Calling Web API to fetch shopping cart items
        $http.get(this.apiPath).success(function(data){
          //Passing data to deferred's resolve function on successful completion
          deferred.resolve(data);
      }).error(function(){

        //Sending a friendly error message in case of failure
        deferred.reject("An error occured while fetching items");
      });

      //Returning the promise object
      return deferred.promise;
    }
  }
}

Following is the controller consuming the above custom service: 
function ShoppingCartCtrl($scope, shoppingData) {
  $scope.items = [];

  function refreshItems(){
    shoppingData.getAllItems().then(function(data){
      $scope.items = data;
    },
    function(errorMessage){
      $scope.error=errorMessage;
    });
  };

  refreshItems();
};

详见：http://sravi-kiran.blogspot.com/2013/03/MovingAjaxCallsToACustomServiceInAngularJS.html