Jasper Reports不在浏览器上显示pdf，在控制台上显示没有错误

Question

这是我的Java类代码的片段

案例1

    request=ServletActionContext.getRequest();
            response = ServletActionContext.getResponse();
            if(response!=null)
                System.out.println("Response is not null");
            System.out.println("coming to this method");
            inputStream= this.getClass().getClassLoader().getResourceAsStream("com/ram/report/jasper/Report.jrxml");
            JasperReport jasperReport=JasperCompileManager.compileReport(inputStream);
            HashMap<String, Object> params = null;

            JasperPrint jp=JasperFillManager.fillReport(jasperReport, params,new JRBeanCollectionDataSource(list));
            JRExporter exporter = new net.sf.jasperreports.engine.export.JRPdfExporter();
            exporter.setParameter(JRExporterParameter.JASPER_PRINT, jp);
            exporter.setParameter(JRExporterParameter.OUTPUT_FILE_NAME, new File("").getAbsolutePath()+"/UserReport.pdf");
            exporter.exportReport();
            File file = new File(new File("").getAbsolutePath()+"/UserReport.pdf"); 

            inputStream  = new FileInputStream(file);
            response.flushBuffer();
            System.out.println("Made report");
            return "ajaxReturn";
        }

案例2

request=ServletActionContext.getRequest();
                response = ServletActionContext.getResponse();
                if(response!=null)
                    System.out.println("Response is not null");
                System.out.println("coming to this method");
                inputStream= this.getClass().getClassLoader().getResourceAsStream("com/ram/report/jasper/Report.jrxml");
                JasperReport jasperReport=JasperCompileManager.compileReport(inputStream);
                HashMap<String, Object> params = null;

                JasperPrint jp=JasperFillManager.fillReport(jasperReport, params,new JRBeanCollectionDataSource(list));
                JRExporter exporter = new net.sf.jasperreports.engine.export.JRPdfExporter();
                exporter.setParameter(JRExporterParameter.JASPER_PRINT, jp);
                exporter.setParameter(JRExporterParameter.OUTPUT_FILE_NAME, new File("").getAbsolutePath()+"/UserReport.pdf");
                exporter.exportReport();
                File file = new File(new File("").getAbsolutePath()+"/UserReport.pdf"); 

                inputStream  = new FileInputStream(file);
                ServletOutputStream op = response.getOutputStream();
                response.setContentType("application/pdf");
                response.setHeader("Content-Disposition",
                        "application; filename=\"" + "UserReport.pdf");
                byte[] bbuf = new byte[50000];
                int length=0;
                while ((inputStream != null) && ((length = inputStream.read(bbuf)) != -1)) {
                    op.write(bbuf, 0, length);
                }
                op.flush();
                op.close(); 
                response.flushBuffer();
                System.out.println("Made report");
                return "ajaxReturn";
            }

这是我的行动

<action name="reportData" class="Reportfetchnew">
<interceptor-ref name="cookie"></interceptor-ref>
 <interceptor-ref name="cookieProvider"></interceptor-ref>
 <interceptor-ref name="defaultStack"></interceptor-ref>
<result name="success">htdocs/jsp/report_new/report_tool.jsp</result>
 <result name="ajaxReturn" type="stream" >
    <param name="contentType">application/pdf</param>
    <param name="contentDisposition">attachment;filename="UserReport.pdf"</param>
    <param name="bufferSize">1024</param>
    <param name="inputName">inputStream</param>

    </result>

我面临的问题是，尽管在Eclipse控制台上没有显示任何错误，但pdf并未在浏览器上显示。
检查几个链接后，我想到镜像到一个outputStream，所以我做了案例2.但是它给出了相同的结果。另外，“Made report”也正在打印，这意味着该文件已在两种情况下创建。那么这里的错误到底是什么？