java.lang.IllegalStateException: getOutputStream() has already been called
java.lang.IllegalStateException: getOutputStream() has already been called for this response
：
JSP ， ：
out.clear()： 。
pageContext.pushBody()： API
public BodyContent pushBody()
Return a new BodyContent object, save the current "out" JspWriter, and update the value of the "out" attribute in the page scope attribute namespace of the PageContext.
Returns:
the new BodyContent
· BodyContent( HTML BODY ）
· JspWriter out
· PageContext out