Java匯出Excel檔案（jxl.jar版）（詳細解讀）

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

public class ExportData
{
public void exportProduct()
{
try
{
//類login(javabean)的managed-bean-scope屬性設定成session，這樣可以調用login中目前使用者的id。這個非常有用。
login me = (login) FacesContext.getCurrentInstance().getExternalContext().getSessionMap().get("login");
String userId = String.valueOf(me.getID_());
//設定匯出檔案在伺服器上的儲存路徑，getBasedir()和getSeparator()根據伺服器OS來判斷當前路徑和串連符，Windows 和Linux不一樣。
String storedir = getBasedir() + userId + getSeparator();
//System.out.println("storedir:" + storedir);
//System.out.println("main.isDirExists(storedir):" + main.isDirExists(storedir));
//如果storedir檔案不存在，就建立它
if(main.isDirExists(storedir))
{
storedir = storedir + "exportExcel.xls";
File file = new File(storedir);
if(file.exists())
file.delete();
//建立一個excel檔案
jxl.write.WritableWorkbook wwb = Workbook.createWorkbook(new File(storedir));
//建立一個活頁簿
jxl.write.WritableSheet ws = wwb.createSheet("data", 0);
//定義excel的文本儲存格
jxl.write.Label label;
//定義excel的數值儲存格
jxl.write.Number number;
//格式化數值
jxl.write.NumberFormat nf = new jxl.write.NumberFormat("#.####");
jxl.write.WritableCellFormat wcNf = new jxl.write.WritableCellFormat(nf);
//從0開始，設定欄位標題
label = new jxl.write.Label(0,0, "物品編碼");
ws.addCell(label);
label = new jxl.write.Label(1,0, "物品描述");
ws.addCell(label);
label = new jxl.write.Label(2,0, "庫存數量");
ws.addCell(label);
label = new jxl.write.Label(3,0, "入庫日期");
ws.addCell(label);
label = new jxl.write.Label(4,0, "在庫天數");
ws.addCell(label);
label = new jxl.write.Label(5,0, "在庫月份");
ws.addCell(label);
label = new jxl.write.Label(6,0, "入庫數量");
ws.addCell(label);
label = new jxl.write.Label(7,0, "成本");
ws.addCell(label);
label = new jxl.write.Label(8,0, "總成本");
ws.addCell(label);
main.oracleSession.clear();
//迴圈提取表中的資料
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