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java.lang.IllegalStateException: getOutputStream() has already been called for this response

时间:2019-12-20 13:36:42      阅读:85      评论:0      收藏:0      [点我收藏+]

标签:重复   color   wrap   protocol   erro   exception   name   star   eva   

1.问题描述:

  在导出数据库某时间段的数据,然后获得Excel,虽然页面可以顺利导出,但后台报错如下:(虽然不影响导出效果,但看到后台的异常,内心还是不舒服的)

严重: Servlet.service() for servlet [jsp] in context with path [/exportExcel] 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:678)
    at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:213)
    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:194)
    at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:126)
    at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:80)
    at org.apache.jsp.export_jsp._jspService(export_jsp.java:566)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:439)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

 从字义上分析:getOutputStream()已经调用了这个响应,就是重复被调用引起的异常。

2.问题分析:

  在tomcat下jsp出现该错误一般都是在使用了输出流(如输出图片验证码,文件下载等)。

  产生这样的异常原因:是web容器生成的servlet代码中有out.write(""),这个和JSP中调用的response.getOutputStream()产生冲突。即Servlet规范说明,不能既调用response.getOutputStream(),又调用response.getWriter(),无论先调用哪一个,在调用第二个时候应会抛出IllegalStateException,因为在jsp中,out变量实际上是通过response.getWriter得到的,你的程序中既用了response.getOutputStream,又用了out变量,故出现以上错误。

3.解决方案:

  在调用 response.getOutputStream()之前,清空缓存的内容,并返回一个新的BodyContext,更新PageContext的out属性的内容。

...
<body>
<%
    String startDate = request.getParameter("startDate");
    String endDate = request.getParameter("endDate");
    System.out.println("起始时间:"+startDate+"  &&&  终止时间"+endDate);
    if(startDate== null || startDate.equals("")){
        startDate = new SimpleDateFormat("yyyy-MM-dd").format(new Date());
        System.out.println("起始时间:"+startDate);
    }
    if(endDate== null || endDate.equals("")){
        endDate = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
        System.out.println(endDate);
    }else{
        endDate = endDate+" 23:59:59";
        System.out.println("终止时间:"+endDate);
    }
    String fileName = new Date().getTime()+".xls";
    response.reset();
    response.setContentType("application/vnd.ms-excel");
    response.setHeader("Content-disposition", "inline;filename="+fileName);
    out.clear();      //清空缓存的内容
    out=pageContext.pushBody();  //更新PageContext的out属性的内容
    writeExcel(response.getOutputStream(),startDate,endDate);
%>
</body>
</html>
<%!    //相当于全局声明,是jsp页面中一些变量和方法的声明时用到的;上面没有感叹号的只是普通的语句 jsp代码块
    public static void writeExcel(OutputStream os,String startDate,String endDate){
        try{
            WritableWorkbook wwb = Workbook.createWorkbook(os);
            WritableSheet sheet = wwb.createSheet("导出表单", 0);  //第一个sheet
            // 设置字体
            WritableFont redfont = new WritableFont(WritableFont.createFont("微软雅黑"),10, WritableFont.BOLD, false, UnderlineStyle.NO_UNDERLINE, Colour.RED);
            // **************往工作表中添加数据*****************
            WritableCellFormat red_key = new WritableCellFormat(redfont);
            WritableFont black_font = new WritableFont(WritableFont.createFont("微软雅黑"),10, WritableFont.BOLD, false, UnderlineStyle.NO_UNDERLINE,Colour.BLACK);
            WritableCellFormat black_key = new WritableCellFormat(black_font);
            // **************往工作表中添加表头*****************
...
...

4.扩展

  上面代码,根本没有用到out,为什么可以调用out.clear和pageContext ? 因为这都是JSP的内置对象,可以随时使用。

  JSP九大内置对象(在JSP页面上可直接使用,html页面不能用):

  4.1 page:一个jsp就是一个servlet类,就是一个java类,java类的this对象,对应JSP的page对象;

  4.2 pageContext :当前页对象

  4.3 application:上下文对象

  4.4 config :servlet生命周期 1.初始化

  4.5 request:请求。servlet生命周期 2.service方法:请求,响应

  4.6 response:响应

  4.7 session:请求对应session,有了request就可以得到session,session=request.getSession();

  4.8 out:response对应out对象--》这个就是这个异常根本所在;

  4.9 exception:异常对象(有代码存在就会有异常存在)。

java.lang.IllegalStateException: getOutputStream() has already been called for this response

标签:重复   color   wrap   protocol   erro   exception   name   star   eva   

原文地址:https://www.cnblogs.com/qingmuchuanqi48/p/12072415.html

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