Java导出Excel文件（jxl.jar版）（详细解读）

import jxl.*;
import jxl.write.*;

public class ExportData
{
    public void exportProduct()
    {
        try
        {  
            //类login(javabean)的managed-bean-scope属性设置成session，这样可以调用login中当前用户的id。这个非常有用。
            login me = (login) FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get("login");
            String userId = String.valueOf(me.getID_());
            //设置导出文件在服务器上的存储路径，getBasedir()和getSeparator()根据服务器OS来判断当前路径和连接符，Windows 和Linux不一样。
            String storedir  = getBasedir() + userId + getSeparator();
            //System.out.println("storedir:" + storedir);
            //System.out.println("main.isDirExists(storedir):" + main.isDirExists(storedir));
            //如果storedir文件不存在，就创建它
            if(main.isDirExists(storedir))
                {
                storedir = storedir + "exportExcel.xls";
                File file = new File(storedir);
                if(file.exists())
                    file.delete();
                //创建一个excel文件
                jxl.write.WritableWorkbook wwb = Workbook.createWorkbook(new File(storedir));
                //创建一个工作簿
                jxl.write.WritableSheet ws = wwb.createSheet("data", 0);
                //定义excel的文本单元格
                jxl.write.Label label;
                //定义excel的数值单元格
                jxl.write.Number number;
                //格式化数值
                jxl.write.NumberFormat nf = new jxl.write.NumberFormat("#.####");
                jxl.write.WritableCellFormat wcNf = new jxl.write.WritableCellFormat(nf);
                //从0开始，设置列标题
                label = new jxl.write.Label(0,0, "物品编码");
                ws.addCell(label);
                label = new jxl.write.Label(1,0, "物品描述");
                ws.addCell(label);
                label = new jxl.write.Label(2,0, "库存数量");
                ws.addCell(label);
                label = new jxl.write.Label(3,0, "入库日期");
                ws.addCell(label);
                label = new jxl.write.Label(4,0, "在库天数");
                ws.addCell(label);
                label = new jxl.write.Label(5,0, "在库月份");
                ws.addCell(label);
                label = new jxl.write.Label(6,0, "入库数量");
                ws.addCell(label);
                label = new jxl.write.Label(7,0, "成本");
                ws.addCell(label);
                label = new jxl.write.Label(8,0, "总成本");
                ws.addCell(label);
                main.oracleSession.clear();
                //循环提取表中的数据
                Query query = main.oracleSession.getNamedQuery("masQuery.selectProductStock");
                      List list = query.list();
                      String pItemCode,pItemDesc,pQuantity,pTranDate,pDays,pMonths,pTranQuantity,pCost,pTotalCost;
                      for(int i=0;i<list.size();i++)
                      {
                        pItemCode=pItemDesc=pQuantity=pTranDate=pDays=pMonths=pTranQuantity=pCost=pTotalCost="";
                           Object obj[] = (Object[])list.get(i);
                           if(obj[0]!=null)
                    pItemCode = String.valueOf(obj[0]);
                        if(obj[1]!=null)
                          pItemDesc = String.valueOf(obj[1]);
                        if(obj[2]!=null)
                             pQuantity = String.valueOf(obj[2]);
                        if(obj[3]!=null)
                          pTranDate = String.valueOf(obj[3]);
                        if(obj[4]!=null)
                          pDays = String.valueOf(obj[4]);
                           if(obj[5]!=null)
                          pMonths = String.valueOf(obj[5]);
                        if(obj[6]!=null)
                          pTranQuantity = String.valueOf(obj[6]);
                        if(obj[7]!=null)
                          pCost = String.valueOf(obj[7]);
                           if(obj[8]!=null)
                          pTotalCost = String.valueOf(obj[8]);
                         //写入数据行
                           label = new jxl.write.Label(0,i+1, pItemCode);
                  ws.addCell(label);
                  label = new jxl.write.Label(1,i+1, pItemDesc);
                  ws.addCell(label);
                  //这一个是数值型数据，没有格式化数据
                  number = new jxl.write.Number(2,i+1, Integer.valueOf(pQuantity));
                  ws.addCell(number);
                  label = new jxl.write.Label(3,i+1, pTranDate);
                  ws.addCell(label);
                  number = new jxl.write.Number(4,i+1, Integer.valueOf(pDays));
                  ws.addCell(number);
                  number = new jxl.write.Number(5,i+1, Integer.valueOf(pMonths));
                  ws.addCell(number);
                  number = new jxl.write.Number(6,i+1, Integer.valueOf(pTranQuantity));
                  ws.addCell(number);
                  //这一个是数值型数据，格式化数据，保留4位小数
                  number = new jxl.write.Number(7,i+1, Float.valueOf(pCost), wcNf);
                  ws.addCell(number);
                  number = new jxl.write.Number(8,i+1, Float.valueOf(pTotalCost), wcNf);
                  ws.addCell(number);
                         }
                //关闭文件
                wwb.write();
                wwb.close();
                myMain my = new myMain();
                //弹出下载框
                my.mDownload(storedir);
                }            
        }catch(Exception ex){ex.printStackTrace();}
    }
}