getOutputStream() has already been called for this response] with root cause

Since the jsp container will call the releasePageContet method to release the used PageContext object after processing the request, and call the getWriter method at the same time, because the getWriter method conflicts with the getOutputStream method related to the use of streams in the jsp page, this exception will be caused. The solution is to :
Just add two statements at the end of the jsp page:  out.clear(); out=pageContext.pushBody(); (where out, pageContext are both jsp built-in objects!) getOutputStream() has already been called for this response] with root cause