============前提加入jar包jxl.jar=========================

// 从数据库导出数据到excel
 public List<Xskh> outPutExcel() {

String url= request.getSession().getServletContext()
     .getRealPath("/")
     + "upload/"; // 创建文件

File dirPath = new File(ctxPath);
   if (!dirPath.exists()) {
    dirPath.mkdir();// 创建文件夹
   }

List<Xskh> list = excelDao.getInfo(" select x from Xskh  ");// 查询数据库导出资料
  try {

WritableSheet sheet = null;
   // 创建excel文件
   WritableWorkbook book = Workbook.createWorkbook(new File(url+"data.xls"));
   // 生成名为“第一页”的工作表，参数0表示这是第一页
   sheet = book.createSheet(" 第一页 ", 0);

// 设置行宽、高
   sheet.getSettings().setDefaultColumnWidth(20);
   sheet.getSettings().setDefaultRowHeight(480);

// 设置字体
   WritableFont font = new WritableFont(WritableFont.ARIAL, 12,
     WritableFont.BOLD, false, UnderlineStyle.NO_UNDERLINE,
     Colour.RED);
   WritableCellFormat wcfF = new WritableCellFormat(font);

// 字体居中
   wcfF.setVerticalAlignment(VerticalAlignment.CENTRE);
   // 自动换行
   wcfF.setWrap(true);

// 在Label对象的构造子中指名单元格位置是第一列第一行(0,0)
   // 以及单元格内容为test
   Label label = new Label(0, 0, "简称 ", wcfF);
   // 将定义好的单元格添加到工作表中
   sheet.addCell(label);
   Label labelcomplay = new Label(1, 0, "公司", wcfF);
   sheet.addCell(labelcomplay);

Label labeltel = new Label(2, 0, "固定电话", wcfF);
   sheet.addCell(labeltel);

Label labelmobile = new Label(3, 0, "移动电话", wcfF);
   sheet.addCell(labelmobile);

Label labelfax = new Label(4, 0, "传真", wcfF);
   sheet.addCell(labelfax);
   Label labeladdr = new Label(5, 0, "地址", wcfF);
   sheet.addCell(labeladdr);
   Label labelsite = new Label(6, 0, "网址", wcfF);
   sheet.addCell(labelsite);

Label labelmail = new Label(7, 0, "邮箱", wcfF);
   sheet.addCell(labelmail);
   Label qq = new Label(8, 0, "qq", wcfF);
   sheet.addCell(qq);
   Label people = new Label(9, 0, "联系人", wcfF);
   sheet.addCell(people);

Label linkbm = new Label(10, 0, "联系人部门", wcfF);
   sheet.addCell(linkbm);
   Label linkejob = new Label(11, 0, "联系人职务", wcfF);
   sheet.addCell(linkejob);
   Label linkphone = new Label(12, 0, "联系人电话", wcfF);
   sheet.addCell(linkphone);

// 所有资料
   for (int i = 0; i < list.size(); i++) {

Label labelad = new Label(0, i + 1, list.get(i).getName());
    sheet.addCell(labelad);
    Label labelmail2 = new Label(1, i + 1, list.get(i).getCompany());
    sheet.addCell(labelmail2);

Label tel = new Label(2, i + 1, list.get(i).getTelephone());
    sheet.addCell(tel);
    Label mobile = new Label(3, i + 1, list.get(i).getMobile());
    sheet.addCell(mobile);
    Label fax = new Label(4, i + 1, list.get(i).getFax());
    sheet.addCell(fax);
    Label addr = new Label(5, i + 1, list.get(i).getAddress());
    sheet.addCell(addr);
    Label site = new Label(6, i + 1, list.get(i).getWww());
    sheet.addCell(site);
    Label mail = new Label(7, i + 1, list.get(i).getEmail());
    sheet.addCell(mail);
    Label q = new Label(8, i + 1, list.get(i).getQq());
    sheet.addCell(q);
    Label peo = new Label(9, i + 1, list.get(i).getLikeme());
    sheet.addCell(peo);
    Label bm = new Label(10, i + 1, list.get(i).getKfPeoBm());
    sheet.addCell(bm);
    Label zw = new Label(11, i + 1, list.get(i).getKfPeoZhiwei());
    sheet.addCell(zw);
    Label linktel = new Label(12, i + 1, list.get(i).getKfPeoTel());
    sheet.addCell(linktel);//创建excel

}

// 写入数据并关闭文件
   book.write();
   book.close();

　　String result = download(request, response, url+ "/data.xls", "data.xls");//下载的方法
   if ("unexists".equals(result)) {
    request.setAttribute("msg", "抱歉，文件不存在，请重新导入文件！");
   } else if ("error".equals(result)) {
    request.setAttribute("msg", "抱歉，当前服务器用户过多，请稍后再试！");
   } else {
    request.setAttribute("msg", "数据导出成功！");

}

} catch (Exception e) {
   e.printStackTrace();
   return null;

}
  return list;
 }

---------------------下载的方法------------------

public  String download(HttpServletRequest request,
   HttpServletResponse response, String urlandfile, String fileName)
   throws Exception {
  String msg = null;
  try {
   response.setCharacterEncoding("UTF-8");
   response.setContentType("text/html");
   javax.servlet.ServletOutputStream ou = response.getOutputStream();
   // 路径
   java.io.File file = new java.io.File(urlandfile);

if (!file.exists()) {
    System.out.println(file.getAbsolutePath() + " 文件不能存在!");
    msg = "unexists";
    return msg;
   }

// 读取文件流
   java.io.FileInputStream fileInputStream = new java.io.FileInputStream(
     file);

// 下载文件
   // 设置响应头和下载保存的文件名

response.setContentType("application/x-msdownload");// 弹出下载的框

response.setContentLength((int) file.length());// 下载统计文件大小的进度
   response.setHeader("Content-Disposition", "attachment; filename="
     + fileName);
   // 下载框的信息
   if (fileInputStream != null) {
    int filelen = fileInputStream.available();
    // 文件太大时内存不能一次读出,要循环

byte a[] = new byte[filelen];

fileInputStream.read(a);

ou.write(a);
   }
   fileInputStream.close();

ou.close();

msg = "success";
  } catch (Exception e) {
   e.printStackTrace();
   msg = "error";

}
  // 解决完成后使用一切正常,但是总抛出java.lang.IllegalStateException异常主要是流还存在
  return msg;
 }