问个用JASPERREPORT生成PDF异常的问题

我JSP的核心代码如下                try {
                                Connection conn = util.Conn.GetConn();
                                // 编译report.jrxml并在report.jrxml所在的目录中生成report.jasper文件
                                File reportFile = new File(application.getRealPath("land.jrxml"));
                                
                                
                                String filepath = reportFile.getParent();
                                JasperCompileManager.compileReportToFile(filepath+ "\\land.jrxml");
                                // 填充数据
                                
                                byte[] bytes = JasperRunManager.runReportToPdf(filepath+"\\land.jasper", null, conn);
                                response.setContentType("application/pdf");
                           // response.setContentLength(bytes.length);
                                ServletOutputStream sOutputStream  = response.getOutputStream();
                                sOutputStream.write(bytes, 0, bytes.length);
                                sOutputStream.flush();
                                sOutputStream.close();                        
                        } catch (Exception e) {
                                e.printStackTrace();
                        }报了如下异常:
2006-11-10 13:36:57 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet jsp threw exception
java.lang.IllegalStateException: getOutputStream() has already been called for this response
        at org.apache.catalina.connector.Response.getWriter(Response.java:599)
        at org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:195)
        at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:124)
        at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:117)
        at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:191)
        at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:115)
        at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:75)
        at org.apache.jsp.index_jsp._jspService(index_jsp.java:106)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:332)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
        at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:833)
        at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:639)
        at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1285)
        at java.lang.Thread.run(Thread.java:595)