JSP中page指令buffer设置为"0kb"后，为什么转发标签<jsp:forward page="">不起作用

设置page指令中buffer="0kb"，转发标签不起作用了

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"
    buffer="0kb"%>
    <%

    %>
<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>Insert title here</title>
        <script src="js/jquery-1.8.3.js" type="text/javascript" charset="utf-8"></script>
    </head>
    <body>
        <form action="forward1.jsp">
            <input type="text" value="123" name="str1"/>
            <button>提交</button>
        </form>

        <%
            out.write("aaaaaaaa");
            out.write("</br>");
            String s1 = request.getParameter("str1"); 
            System.out.print("s1:"+s1);
            if(s1!=null){
                if("中文".equals(s1)){
                    out.write("bbbb");
        %>
        <jsp:forward page="forward2.jsp"></jsp:forward>

        <%} else { %>
        <jsp:forward page="forward3.jsp"></jsp:forward>
        <%}} %>

    </body>
    <script type="text/javascript">

    </script>
</html>

## 结果如下，forward2，forward3完全没有转发

没有转发，并且会出现以下异常

八月 30, 2020 10:40:45 上午 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet [jsp] in context with path [/JavaWeb-JSP_EL_JSTL] threw exception [An exception occurred processing JSP page [/forward1.jsp] at line [25]

22:             if(s1!=null){
23:                 if("中文".equals(s1)){
24:         %>
25:         <jsp:forward page="forward2.jsp"></jsp:forward>
26:         
27:         <%} else { %>
28:         <jsp:forward page="forward3.jsp"></jsp:forward>


Stacktrace:] with root cause
java.lang.IllegalStateException: Illegal to clear() when buffer size == 0
    at org.apache.jasper.runtime.JspWriterImpl.clear(JspWriterImpl.java:143)
    at org.apache.jasper.runtime.PageContextImpl.doForward(PageContextImpl.java:721)
    at org.apache.jasper.runtime.PageContextImpl.forward(PageContextImpl.java:712)
    at org.apache.jsp.forward1_jsp._jspService(forward1_jsp.java:138)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:650)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)