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

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console输出：

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SEVERE: Servlet.service() for servlet [jsp] in context with path [/Test] threw exception [java.lang.IllegalStateException: getOutputStream() has already been called for this response] with root cause  
java.lang.IllegalStateException: getOutputStream() has already been called for this response  
at org.apache.catalina.connector.Response.getWriter(Response.java:639)  
at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:214)  
at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)  
at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)  
at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:190)  
at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:126)  
at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:80)  
at org.apache.jsp.index_jsp._jspService(index_jsp.java:116)  
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)  
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)  
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)  
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)  
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)  
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)  
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)  
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)  
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)  
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)  
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)  
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)  
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)  
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)  
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)  
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1002)  
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)  
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)  
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)  
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)  
at java.lang.Thread.run(Thread.java:722)

getOutputStream() has already been called for this response这个问题今天又遇到了。
起因是写一个http服务，在index.jsp里面直接调用了server(request,response)。
具体的原因：jsp编译成servlet之后在函数
_jspService(HttpServletRequest request, HttpServletResponse response)的最后有一段如下代码：

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finally {    
      if (_jspxFactory != null)     
          _jspxFactory.releasePageContext(_jspx_page_context);    
}

这里是在释放在jsp中使用的对象，会调用response.getWriter(),因为这个方法是和response.getOutputStream()相冲突的！所以会出现以上这个异常。

要解决只需要在index.jsp调用server(request,response) 加上如下代码即可

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out.clear();   
out=pageContext.pushBody();

贴上jsp内容

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<%@page import="com.ct.Server"%>  
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>  
<%  
String path = request.getContextPath();  
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";  
Server.post(request, response);  
out.clear();   
out=pageContext.pushBody();  
%>  

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">  
<html>  
  <head>  
    <base href="<%=basePath%>">  
  
    <title>index</title>  
    <meta http-equiv="pragma" content="no-cache">  
    <meta http-equiv="cache-control" content="no-cache">  
    <meta http-equiv="expires" content="0">      
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">  
    <meta http-equiv="description" content="This is my page">  
    <!-- 
    	<link rel="stylesheet" type="text/css" href="styles.css"> 
    -->  
  
  
  </head>  
    
  <body>  
  </body>  
</html>