jsp + servlet +jxl 实现 export excel

 写一个jsp文件,然后把要从数据库取出数据的sql语句传到servlet 中.
java 代码:
package exportExcel;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import jxl.Workbook;
import jxl.write.Label;
import jxl.write.WritableCellFormat;
import jxl.write.WritableFont;
import jxl.write.WritableSheet;
import jxl.write.WritableWorkbook;
import jxl.write.WriteException;
import jxl.write.biff.RowsExceededException;
public class exportExcel extends HttpServlet{
 @Override
 protected void doPost(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {
  try {
   
  String sqlStr  = (String) req.getParameter("exSql").toLowerCase();
  String sqlS = sqlStr.split("from")[0];
  String sqls = sqlS.split("select")[1];
  //System.out.println(sqls);
  String[] Sql;
  List list = new ArrayList();
  String excelName = req.getParameter("exName");                                     
  HttpSession session = req.getSession();
  String jdbc_driver=(String) session.getAttribute("jdbc_driver");
  String jdbc_url = (String) session.getAttribute("jdbc_url");
  String jdbc_username= (String)session.getAttribut