code: public Object getAttribute(String name) {
          Object value = null;
          synchronized (mutex) {
              if (deleteAttributes != null && deleteAttributes.contains(name)) {
                  return null;
              }
              value = window.get(name);
              if (value == null) {
                  value = super.getAttribute(name);
              }
          }
          return value;
      }
docs: 返回这个窗口的私有属性或portal主控请求对象的共同属性
  
  @param name Name of the attribute to retrieve