angular form-data文件上传

$http({
　　method: ‘POST‘,
　　url: ‘/wechatapp/User/setAvatar‘,
   data: data,
   headers: {
        ‘Content-Type‘: undefined
   },
   transformRequest: function(data) {
       var formData = new FormData();
       formData.append(‘avatar_data‘, data.adata);
       formData.append(‘avatar_file‘, data.file);
       return formData;
   },
   data: {
       adata: scope.avatar_data,
       file: scope.avatar_file
   }
   }).success(function(d) {
       //请求成功
       cb(d);
   }).error(function(err, status) {
       console.log(err);
       cb(err);
   });