第一次調用時response.getOutputStream（）拋出IllegalStateException

Question

我正在嘗試從MySQL-DB下載pdf（我以Blob的形式獲取它，到那時為止一切正常。但是，當我嘗試獲取ServletOutputstream將其發送給客戶端時，程序崩潰。

AFAIK之前調用方法或getwriter方法已調用時，將引發異常。 但是我根本沒有在代碼中使用getwriter方法，並且程序中的其他getOutPutStream方法都沒有達到（我將其注釋掉以確保）。
（如果由於某種原因這很重要，那么整個事情就會在JSP中發生）

這是我的代碼段和異常：

碼

Blob pdf = null;
if(request.getParameter("reportId") != null){
    pdf = testszenario.getReportErgebnisPdf(Integer.parseInt(request.getParameter("reportId")), request.getParameter("erzeugung"));
}
byte[] buf = new byte[(int)pdf.length()];
InputStream inputStream  = pdf.getBinaryStream();
inputStream.read(buf);
inputStream.close();
response.setContentType("application/pdf");
response.setHeader("Content-disposition","attachment; filename=test.pdf"); 

ServletOutputStream sos = response.getOutputStream();
// response.getOutputStream().write(buf);

例外

26.03.2013 09:28:29 org.apache.catalina.core.ApplicationDispatcher invoke
SCHWERWIEGEND: Servlet.service() for servlet jsp threw exception
java.lang.IllegalStateException
    at org.apache.jasper.runtime.ServletResponseWrapperInclude.getOutputStream(ServletResponseWrapperInclude.java:63)
    at org.apache.jsp.jsp.modules.Testszenario.PostReportResultOverview_jsp._jspService(PostReportResultOverview_jsp.java:115)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:630)
    at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:535)
    at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:472)
    at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:968)
    at org.apache.jsp.jsp.McFrame_jsp._jspService(McFrame_jsp.java:284)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
    at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
    at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
    at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
    at java.lang.Thread.run(Thread.java:619)

Answer 1

請檢查您的回復是否已落實。 如果您嘗試對已提交的響應進行操作，則可能會出現IllegalStateException 。 如果超出頁面緩沖區大小，將提交響應。

Answer 2

在JSP中執行此操作確實很重要。 請記住，JSP是Web應用程序請求的輸出呈現階段的一部分，因此容器可能已經獲取了writer對象。 嘗試將代碼移入servlet。 它可以讓您更好地控制編寫器/流。