Display Excel sheet in the Browser?

I need to display the newly generated excel (from tables using Apache POI) in a web browser (whatever it is, Firefox, Opera or IE). I've created the JSP file with

contentType="application/vnd.ms-excel"

But I'm not getting it.

Here's my code snippet :

<%@page session="true" contentType="application/vnd.ms-excel" pageEncoding="UTF-8"%>
<%@page import="org.apache.poi.ss.usermodel.CellStyle"%>
<%@page import="java.sql.DriverManager"%>
<%@page import="java.sql.ResultSet"%>
<%@page import="java.sql.Statement"%>
<%@page import="java.sql.Connection"%>
<%@page import="org.apache.poi.ss.usermodel.CreationHelper"%>
<%@page import="org.apache.poi.hssf.usermodel.HSSFCell"%>
<%@page import="org.apache.poi.hssf.usermodel.HSSFRow"%>
<%@page import="org.apache.poi.hssf.usermodel.HSSFWorkbook"%>
<%@page import="org.apache.poi.hssf.usermodel.HSSFSheet"%>

<html>
    <head>
        <%!
            int r=0;

            HSSFWorkbook book;
            HSSFSheet sheet;
            HSSFRow row;

            CreationHelper createHelper = book.getCreationHelper();

            Connection conn;
            Statement stmt;
            ResultSet rs;
        %>
        <title>Report</title>
        <%
            book = new HSSFWorkbook();
            sheet = book.createSheet("Report");
        %>
    </head>
    <body>
        <%
            try     {

                    // Header of the Excel File
                row = sheet.createRow(r);

                row.createCell(0).setCellValue("Visit ID");
                row.createCell(1).setCellValue("Carrier Name");
                row.createCell(2).setCellValue("Phone Number");
                row.createCell(3).setCellValue("Patient Name");
                row.createCell(4).setCellValue("Subscriber ID");
                row.createCell(5).setCellValue("Subscriber Name");
                row.createCell(6).setCellValue("Chart Number");
                row.createCell(7).setCellValue("Date Of Birth");
                row.createCell(8).setCellValue("Subscriber Employer");
                row.createCell(9).setCellValue("Service Date");
                row.createCell(10).setCellValue("Provider Name");
                row.createCell(11).setCellValue("CPT Code");
                row.createCell(12).setCellValue("Aging Date");
                row.createCell(13).setCellValue("Total");
                row.createCell(14).setCellValue("Follow Up Notes");
                row.createCell(15).setCellValue("Internal Status Code");

                CellStyle cellStyle = book.createCellStyle();
                cellStyle.setDataFormat(createHelper.createDataFormat().getFormat("MM/dd/yyyy"));

                Statement stNotes;
                ResultSet rsNotes;

                Class.forName("com.mysql.jdbc.Driver");

                conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/maintain", "root", "root");
                stmt = conn.createStatement();

                stNotes = conn.createStatement();

                rs = stmt.executeQuery("SELECT b.VisitID, b.CarrierName, b.PhoneNum, b.PatientName, "
                        + "b.SubscriberID, b.SubscriberName, b.ChartNum, b.DoB, b.SubscriberEmp, "
                        + "b.ServiceDate, b.ProviderName, b.CPTCode, b.BillingDate, b.BalanceAmt "
                        + "FROM billing b INNER JOIN followup f ON b.VisitID = f.VisitID GROUP BY VisitID");

                while(rs.next())    {
                    r++;

                    row = sheet.createRow(r);

                    row.createCell(0).setCellValue(rs.getString("VisitID"));
                    row.createCell(1).setCellValue(rs.getString("CarrierName"));
                    row.createCell(2).setCellValue(rs.getString("PhoneNum"));
                    row.createCell(3).setCellValue(rs.getString("PatientName"));
                    row.createCell(4).setCellValue(rs.getString("SubscriberID"));
                    row.createCell(5).setCellValue(rs.getString("SubscriberName"));
                    row.createCell(6).setCellValue(rs.getString("ChartNum"));
                    row.createCell(7).setCellValue(rs.getString("DoB"));
                    row.createCell(8).setCellValue(rs.getString("SubscriberEmp"));


                    row.createCell(9).setCellValue(rs.getString("ServiceDate"));
                    row.createCell(9).setCellStyle(cellStyle);

                    row.createCell(10).setCellValue(rs.getString("ProviderName"));
                    row.createCell(11).setCellValue(rs.getString("CPTCode"));

                    row.createCell(12).setCellValue(rs.getString("BillingDate"));
                    row.createCell(12).setCellStyle(cellStyle);

                    row.createCell(13).setCellValue(rs.getString("BalanceAmt"));

                    rsNotes = stNotes.executeQuery("SELECT Date, InternalStatusCode, FollowUpNote "
                            + "FROM followup WHERE VisitID='" + rs.getString("VisitID") + "' ORDER BY Date");

                    while(rsNotes.next())   {
                        row.createCell(14).setCellValue(rsNotes.getString("Date") + " - " + rsNotes.getString("FollowUpNote"));
                        row.createCell(15).setCellValue(rs.getString("VisitID"));
                    }
                }

            }
            catch(ClassNotFoundException cnf) {
                out.print("<br> Error : MySQL Driver not found. <br>");
            }
            catch(Exception ex)  {
                out.print("Error :  <br>" + ex);
            }
        %>
    </body>
</html>

I'm getting this exception with Tomcat 6.0.26 :

exception

org.apache.jasper.JasperException: java.lang.NullPointerException
    org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:156)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:329)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

root cause

java.lang.NullPointerException
    org.apache.jsp.GetReport_jsp.<init>(GetReport_jsp.java:29)
    sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    java.lang.reflect.Constructor.newInstance(Constructor.java:513)
    java.lang.Class.newInstance0(Class.java:355)
    java.lang.Class.newInstance(Class.java:308)
    org.apache.jasper.servlet.JspServletWrapper.getServlet(JspServletWrapper.java:145)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:329)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

Did I miss something or anything wrong? Can anybody help me to get rid of this problem?

Thanx in advance.

回答1:

The way you are trying to do it doesn't make any sense. You can't mix HTML with Excel like that. Better create a servlet instead of a JSP page and let this servlet output only the Excel file and nothing else.

Something like this:

import java.io.*;    
import javax.servlet.http.*;
import javax.servlet.*;
import org.apache.poi.hssf.usermodel.HSSFWorkbook;
// ... plus all the other libs you need

public class ExcelServlet extends HttpServlet {
  public void doGet (HttpServletRequest req,
                     HttpServletResponse res)
    throws ServletException, IOException
  {
    HSSFWorkbook book;
    // ...
    // fill the book
    // ...
    res.setContentType("application/vnd.ms-excel");
    book.write(res.getOutputStream());
    res.getOutputStream().close();
  }
}

回答2:

HSSFWorkbook book;
HSSFSheet sheet;
HSSFRow row;
CreationHelper createHelper = book.getCreationHelper();

You are using the book object before initializing it.

回答3:

I'd recommend not doing it this way.

Scriptlet code in JSPs is simply wrong.

Putting database access in a page like this isn't good, either.

A better approach would be Spring MVC and its JExcelView.

回答4:

Here's a tip on how to debug JSP exceptions:

in the stacktrace, this class

java.lang.NullPointerException
org.apache.jsp.GetReport_jsp.<init>(GetReport_jsp.java:29)

is the generated java class for your GetReport.jsp. You can look in the $TOMCAT_HOME/work/<enginename>/<hostname>/<appname> folder to see the actual code generated, and see what exactly is at line 29.

回答5:

Take a look at WorkbookTag project from SourceForge which does exactly what you need: HTML worksheet rendering using Apache POI... WorkbookTag