function init_tree(product_name) {
  var htmlobj=$.ajax({url: "get_all_file?param=" + param_value,  async: false});
  var jsonNodes = htmlobj.responseText;
  var newNodes = $.parseJSON(jsonNodes);
  //使用newNodes更新页面
}

def get_all_file
    # 为@file_tree赋值
    @file_tree=[{:id => code, :pId => p_code, :name => file}, {:id => code1, :pId => p_code1, :name => file1}]
    respond_to do |format|
      format.json { render :json=> @file_tree }
    end
  end