Export to Excel from Database using JSP

Question

Hi Experts,
I'm using below jsp code to export from an Oracle table to Excel using JSP.
Every time I run this code I get the exception - "java.lang.OutOfMemoryError: Java heap space".
I need to download around 8000+ records of the table containing 60 columns.
I have increased Heap space but still the exception. Below is the code for your reference (I have mentioned only 30 columns where as there are 60 columns in actual). Pls help me what could be the other possible ways or suggest me any alternate code.
Pls note - Some of the terms like "<serverip>", MySchema, myfile, COL names are changed for confidentiality.
"D:\\Myfolder\\Excelfolder\\Final.xls" exists my the local machine.
The code works until some 4000 records & after that throws the exception.
try
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection = DriverManager.getConnection("jdbc:oracle:thin:@<serverip>:1521:WISTGDEV", "user", "user@123");
Statement statement = connection.createStatement();
String filename = "C:\\Myfolder\\Excelfolder\\Final.xls";
String strQuery1 = ("select * from Myschema.myfile");
ResultSet rs = statement.executeQuery(strQuery1);
HSSFWorkbook hwb = new HSSFWorkbook();
HSSFSheet sheet = hwb.createSheet("sheet1");
HSSFRow rowhead = sheet.createRow((short)0);
rowhead.createCell((short) 0).setCellValue("COL1");
rowhead.createCell((short) 1).setCellValue("COL2");
rowhead.createCell((short) 2).setCellValue("COL3");
rowhead.createCell((short) 3).setCellValue("COL4");
rowhead.createCell((short) 4).setCellValue("COL5");
rowhead.createCell((short) 5).setCellValue("COL6");
rowhead.createCell((short) 6).setCellValue("COL7");
rowhead.createCell((short) 7).setCellValue("COL8");
rowhead.createCell((short) 8).setCellValue("COL9");
rowhead.createCell((short) 9).setCellValue("COL10");
rowhead.createCell((short) 10).setCellValue("COL11");
rowhead.createCell((short) 11).setCellValue("COL12");
rowhead.createCell((short) 12).setCellValue("COL13");
rowhead.createCell((short) 13).setCellValue("COL14");
rowhead.createCell((short) 14).setCellValue("COL15");
rowhead.createCell((short) 15).setCellValue("COL16");
rowhead.createCell((short) 16).setCellValue("COL17");
rowhead.createCell((short) 17).setCellValue("COL18");
rowhead.createCell((short) 18).setCellValue("COL19");
rowhead.createCell((short) 19).setCellValue("COL20");
rowhead.createCell((short) 20).setCellValue("COL21");
rowhead.createCell((short) 21).setCellValue("COL22");
rowhead.createCell((short) 22).setCellValue("COL23");
rowhead.createCell((short) 23).setCellValue("COL24");
rowhead.createCell((short) 24).setCellValue("COL25");
rowhead.createCell((short) 25).setCellValue("COL26");
rowhead.createCell((short) 26).setCellValue("COL27");
rowhead.createCell((short) 27).setCellValue("COL28");
rowhead.createCell((short) 28).setCellValue("COL29");
rowhead.createCell((short) 29).setCellValue("COL30");
int index=1
String name="";
while(rs.next())
System.out.println("Inside while");
HSSFRow row = sheet.createRow((short)index);
row.createCell((short) 0).setCellValue(rs.getString(2));
row.createCell((short) 1).setCellValue(rs.getString(3));
row.createCell((short) 2).setCellValue(rs.getString(4));
row.createCell((short) 13).setCellValue(rs.getFloat(5));
row.createCell((short) 4).setCellValue(rs.getString(6));
row.createCell((short) 5).setCellValue(rs.getString(7));
row.createCell((short) 6).setCellValue(rs.getInt(8));
row.createCell((short) 7).setCellValue(rs.getString(9));
row.createCell((short) 8).setCellValue(rs.getString(10));
row.createCell((short) 9).setCellValue(rs.getString(11));
row.createCell((short) 10).setCellValue(rs.getString(12));
row.createCell((short) 11).setCellValue(rs.getFloat(13));
row.createCell((short) 12).setCellValue(rs.getFloat(14));
row.createCell((short) 13).setCellValue(rs.getFloat(15));
row.createCell((short) 14).setCellValue(rs.getFloat(16));
row.createCell((short) 15).setCellValue(rs.getFloat(17));
row.createCell((short) 16).setCellValue(rs.getFloat(18));
row.createCell((short) 17).setCellValue(rs.getFloat(19));
row.createCell((short) 18).setCellValue(rs.getFloat(20));
row.createCell((short) 19).setCellValue(rs.getFloat(21));
row.createCell((short) 20).setCellValue(rs.getFloat(22));
row.createCell((short) 21).setCellValue(rs.getString(23));
row.createCell((short) 22).setCellValue(rs.getString(24));
row.createCell((short) 23).setCellValue(rs.getString(25));
row.createCell((short) 24).setCellValue(rs.getString(26));
row.createCell((short) 25).setCellValue(rs.getString(27));
row.createCell((short) 26).setCellValue(rs.getString(28));
row.createCell((short) 27).setCellValue(rs.getString(29));
row.createCell((short) 28).setCellValue(rs.getString(30));
index++;
rs.close();
FileOutputStream fileOut = new FileOutputStream(filename);
hwb.write(fileOut);
fileOut.close();
connection.close();
catch(Exception e)
System.out.println(e.getMessage());
e.printStackTrace();
Thanks in advance,
Venky
Edited by: Venky_86 on Apr 15, 2009 12:06 AM

Answer 1

Its is an obvious thing...POI is known to need a lot of memory (the reason for that is most likely the OLE document format, which is quite complex).
I would have used something like the below to see if that can address my client's requirement.
public exportExcel(String fileName){
   Connection connection = null;
   Statement statement = null;
   ResultSet rs = null;
   PrintWriter out = null;
   int index=1;
   try{
     out = new PrintWrite(new FileWriter(fileName));
     connection = DbUtils.getConnection();
     statement = connection.createStatement();
     rs = statement.executeQuery("select * from Myschema.myfile");
     out.prinln("<table>");
     out.println("<th>COL1</th>");
     out.println("<th>COL2</th>");
     out.println("<th>COL3</th>");
     out.println("<th>COL4</th>");
     out.println("<th>COL5</th>");
     out.println("<th>COL6</th>");
     out.println("<th>COL7</th>");
     out.println("<th>COL8</th>");
     out.println("<th>COL9</th>");
    out.println("<th>COL30</th>");
     out.println("<thead>");
     out.println("<tbody>");
     while(rs.next()){
          out.println("<td>"+index+"</td>");
          out.println("<td>"+rs.getString(2)+"<td>");        
          out.println("<td>"+rs.getString(3)+"<td>");        
          out.println("<td>"+rs.getString(4)+"<td>");        
          out.println("<td>"+rs.getString(5)+"<td>");        
          out.println("<td>"+rs.getString(6)+"<td>");        
          out.println("<td>"+rs.getString(7)+"<td>");        
          out.println("<td>"+rs.getString(8)+"<td>");        
          out.println("<td>"+rs.getString(9)+"<td>");        
          out.println("<td>"+rs.getString(30)+"<td>");        
     out.println("</tbody>")     
     out.println("</table>");    
     out.flush(); 
   }catch(Exception exp){
       exp.printStackTrace();
   }finally{
       if(out != null)
        try{out.close();}catch(Exception e){}
         if(rs != null)
           try{rs.close();}catch(Exception e){}
        if(statement != null)
           try{statement.close();}catch(Exception e){}
         if(connection != null)
           try{connection.close();}catch(Exception e){}
}and you can simply export the file using the method
ApplicationUtils.getInstance().exportExcel("c:/export/myapp/ApplicationTable.xls");If you are using Office 2000 and above you should able open it as an excel worksheet without any problems.
Hope that help :)
REGARDS,
RaHuL