先說結論，通過 HttpServletResponse 得到的 PrintWriter 和 ServletOutputStream 不需要手動關閉。
Normally you should not close the stream.
The servlet container will automatically close the stream
after the servlet is finished running as part of the servlet request life-cycle.
通常您不應該關閉流。在 servlet 完成生命周期之后，servlet 容器會自動關閉流。
For instance, if you closed the stream it would not be available if you implemented a Filter.
舉個例子，如果你關閉了流的話，在你實現的 Filter 中就不能再使用了。
Having said all that, if you do close it nothing bad will happen as long as you don't try to use it again.
說了這么多，如果你不再使用流了的話，即使關閉了也不會有任何壞影響。