AngularJS returns Object object

Question

I have a backend REST service that returns an array. I am trying to display the value returned by this REST service in one of my <select> using ng-options. However I get [object Object] on the lists.

Backend Java Rest service

@Path("/positions")
public class PositionRestService {

    ManagerService managerService = new ManagerService();   

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    public List<String> getVacantPositions(@HeaderParam("iv-user") String uid) throws Exception{  
        Manager manager = managerService.getManager(uid);
        LdapSearch ldapProfile = new LdapSearch();
        List<String> vacantPositions = new ArrayList<String>();
        vacantPositions = ldapProfile.getChildPositions(manager.getPositionID());
        return vacantPositions;
    }
}

AngularJS Code - Service.js

services.factory('PositionsFactory', function ($resource) {
        return $resource('/userfeed/rest/positions', {}, {
            query: { method: 'GET', isArray: true}
        })

});

AngularJS - Controller.js

 app.controller('PositionCtrl', ['$scope', 'PositionsFactory', function ($scope, PositionsFactory) {    
    //$scope.positions = PositionsFactory.query();
    PositionsFactory.query({}, function (positionsFactory) {
        $scope.positions = positionsFactory;        
    })
}]);

My HTML code that uses the controller

 <select ng-model="myPosition" ng-options="position as position for position in positions"> </select>

Result I seee the follwing options on my list of options.

[object Object]

When I access the REST Service using my browser, I get the following array result which is what I am expecting on my option box above.

["CU13-00-00-004-","CU13-00-00-005-","CU13-00-00-006-"]

How can I get the values CU13-00-00-004-, CU13-00-00-005- and CU13-00-00-006- on my options using ng-options.

On using

{{positions|json}}

, I get following outcome:

[

{ "0": "C", "1": "U", "2": "1", "3": "3", "4": "-", "5": "0", "6": "0", "7": "-", "8": "0", "9": "0", "10": "-", "11": "0", "12": "0", "13": "4", "14": "-" }, { "0": "C", "1": "U", "2": "1", "3": "3", "4": "-", "5": "0", "6": "0", "7": "-", "8": "0", "9": "0", "10": "-", "11": "0", "12": "0", "13": "5", "14": "-" }, { "0": "C", "1": "U", "2": "1", "3": "3", "4": "-", "5": "0", "6": "0", "7": "-", "8": "0", "9": "0", "10": "-", "11": "0", "12": "0", "13": "6", "14": "-" } ]

Looks like it has converted the array into JSON object and created a place holder for earch character. The with ng-options show them as [object Object].

Please help. Any suggestion would be much appreciated.