java.lang.IllegalStateException: getOutputStream() has already been called for this response
1.問題描述:
在導出數據庫某時間段的數據,然後獲得Excel,雖然頁面可以順利導出,但後臺報錯如下:(雖然不影響導出效果,但看到後臺的異常,內心還是不舒服的)
複製代碼
嚴重: 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)
複製代碼
從字義上分析:getOutputStream()已經調用了這個響應,就是重複被調用引起的異常。
2.問題分析:
在tomcat下jsp出現該錯誤一般都是在使用了輸出流(如輸出圖片驗證碼,文件下載等)。
產生這樣的異常原因:是web容器生成的servlet代碼中有out.write(""),這個和JSP中調用的response.getOutputStream()產生衝突。即Servlet規範說明,不能既調用response.getOutputStream(),又調用response.getWriter(),無論先調用哪一個,在調用第二個時候應會拋出IllegalStateException,因爲在jsp中,out變量實際上是通過response.getWriter得到的,你的程序中既用了response.getOutputStream,又用了out變量,故出現以上錯誤。
3.解決方案:
在調用 response.getOutputStream()之前,清空緩存的內容,並返回一個新的BodyContext,更新PageContext的out屬性的內容。
複製代碼
...
<body>
<%
String startDate = request.getParameter("startDate");
String endDate = request.getParameter("endDate");
System.out.println("起始時間:"+startDate+" &&& 終止時間"+endDate);
if(startDate== null || startDate.equals("")){
startDate = new SimpleDateFormat("yyyy-MM-dd").format(new Date());
System.out.println("起始時間:"+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("終止時間:"+endDate);
}
String fileName = new Date().getTime()+".xls";
response.reset();
response.setContentType("application/vnd.ms-excel");
response.setHeader("Content-disposition", "inline;filename="+fileName);
*out.clear(); //清空緩存的內容
out=pageContext.pushBody(); //更新PageContext的out屬性的內容*
writeExcel(response.getOutputStream(),startDate,endDate);
%>
</body>
</html>
<%! //相當於全局聲明,是jsp頁面中一些變量和方法的聲明時用到的;上面沒有感嘆號的只是普通的語句 jsp代碼塊
public static void writeExcel(OutputStream os,String startDate,String endDate){
try{
WritableWorkbook wwb = Workbook.createWorkbook(os);
WritableSheet sheet = wwb.createSheet("導出表單", 0); //第一個sheet
// 設置字體
WritableFont redfont = new WritableFont(WritableFont.createFont("微軟雅黑"),10, WritableFont.BOLD, false, UnderlineStyle.NO_UNDERLINE, Colour.RED);
// **************往工作表中添加數據*****************
WritableCellFormat red_key = new WritableCellFormat(redfont);
WritableFont black_font = new WritableFont(WritableFont.createFont("微軟雅黑"),10, WritableFont.BOLD, false, UnderlineStyle.NO_UNDERLINE,Colour.BLACK);
WritableCellFormat black_key = new WritableCellFormat(black_font);
// **************往工作表中添加表頭*****************
...
...
複製代碼
4.擴展
上面代碼,根本沒有用到out,爲什麼可以調用out.clear和pageContext ? 因爲這都是JSP的內置對象,可以隨時使用。
JSP九大內置對象(在JSP頁面上可直接使用,html頁面不能用):
4.1 page:一個jsp就是一個servlet類,就是一個java類,java類的this對象,對應JSP的page對象;
4.2 pageContext :當前頁對象
4.3 application:上下文對象
4.4 config :servlet生命週期 1.初始化
4.5 request:請求。servlet生命週期 2.service方法:請求,響應
4.6 response:響應
4.7 session:請求對應session,有了request就可以得到session,session=request.getSession();
4.8 out:response對應out對象–》這個就是這個異常根本所在;
4.9 exception:異常對象(有代碼存在就會有異常存在)。