先说结论，通过 HttpServletResponse 得到的 PrintWriter 和 ServletOutputStream 不需要手动关闭。
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.
通常您不应该关闭流。在 servlet 完成生命周期之后，servlet 容器会自动关闭流。
For instance, if you closed the stream it would not be available if you implemented a Filter.
举个例子，如果你关闭了流的话，在你实现的 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.
说了这么多，如果你不再使用流了的话，即使关闭了也不会有任何坏影响。