I don't see the error! help?

Question

here's the JSP codes. It is suppose to process data from the database to PDF format
<%@ page import="java.sql.*,
     java.io.*,
     javax.servlet.http.*,
     javax.servlet.*,
     com.lowagie.text.*,
     com.lowagie.text.pdf.PdfWriter"
errorPage="" %>
<%@ include file="Connections/test.jsp" %>
<%
Driver DriverRecordset1 = (Driver)Class.forName(MM_test_DRIVER).newInstance();
Connection ConnRecordset1 = DriverManager.getConnection(MM_test_STRING,MM_test_USERNAME,MM_test_PASSWORD);
PreparedStatement StatementRecordset1 = ConnRecordset1.prepareStatement("SELECT MODCD, COUNT('ADMNO') AS NumQues FROM StudentModule GROUP BY MODCD ORDER BY MODCD");
ResultSet Recordset1 = StatementRecordset1.executeQuery();
boolean Recordset1_isEmpty = !Recordset1.next();
boolean Recordset1_hasData = !Recordset1_isEmpty;
Object Recordset1_data;
int Recordset1_numRows = 0;
%>
<%
response.setContentType( "application/pdf" );
// step 1: creation of a document-object
Document document = new Document();
// step 2:
// we create a writer that listens to the document
// and directs a PDF-stream to a temporary buffer
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
PdfWriter.getInstance( document, buffer );
// step 3: we open the document
document.open();
// step 4: we add a paragraph to the document
     Table aTable = new Table(6,2); // 2 rows, 2 columns
     do {
     String modcode = Recordset1.getString("MODCD");
     String NumStud = Recordset1.getString("NumQues");
aTable.addCell("modcode");
aTable.addCell("NumStud");      
     } while (Recordset1.next());
     document.add(aTable);
// step 5: we close the document
document.close();
%>
<%
// step 6: we output the writer as bytes to the response output
DataOutput output = new DataOutputStream( response.getOutputStream() );
byte[] bytes = buffer.toByteArray();
response.setHeader("Cache-Control", "max-age=0");
response.setHeader("Content-Disposition", "attachment;filename=pdfdemo.pdf");
response.setContentLength(bytes.length);
for( int i = 0; i < bytes.length; i++ ) { output.writeByte( bytes[i] ); }
%>
<%
Recordset1.close();
StatementRecordset1.close();
ConnRecordset1.close();
%>
Sorry for the messy codes (:
Error was a pile of stack trace in the web browser which i don't even understand

Answer 1

i am thinking of using servlets too...but just wanna give it a shot with JSP.
the stack trace is pretty long...
here it is:
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException: getOutputStream() has already been called for this response
     at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:254)
     at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
     at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
     at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
     at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
     at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2417)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
     at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
     at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
     at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
     at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:193)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:781)
     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:549)
     at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:589)
     at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:666)
     at java.lang.Thread.run(Thread.java:536)
root cause
java.lang.IllegalStateException: getOutputStream() has already been called for this response
     at org.apache.coyote.tomcat4.CoyoteResponse.getWriter(CoyoteResponse.java:600)
     at org.apache.coyote.tomcat4.CoyoteResponseFacade.getWriter(CoyoteResponseFacade.java:171)
     at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:173)
     at org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:166)
     at org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:184)
     at org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:198)
     at org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:193)
     at org.apache.jsp.convertPDF_jsp._jspService(convertPDF_jsp.java:128)
     at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:137)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
     at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:210)
     at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:295)
     at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:256)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
     at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
     at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
     at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2417)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
     at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:171)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:172)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:641)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
     at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
     at org.apache.catalina.core.StandardPipeline$StandardPipelineValveContext.invokeNext(StandardPipeline.java:643)
     at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:480)
     at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:995)
     at org.apache.coyote.tomcat4.CoyoteAdapter.service(CoyoteAdapter.java:193)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:781)
     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:549)
     at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:589)
     at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:666)
     at java.lang.Thread.run(Thread.java:536)
if i can't find a solution today, guess i'll stick with servlets