poi导出excel（这个比较好）

实现方式如下：

页面设计：

<td width="100" align="center"><a href="#" onclick="doExport();return false;" class="blue bold">导出内容到excel</a></td>

function doExport(){

        var dataV=window.showModalDialog("<c:out value='${ctx}'/>/task/dialog.jsp","","dialogWidth=250px;dialogHeight=220px");
    if(dataV !=null && dataV != ""){
        if(dataV == '1'){
            var eleForm = $("pageQueryForm");
         var lastAction = eleForm.action;
         var ExportAll = $("ExportAll");
         if(ExportAll != null){
            eleForm.removeChild(ExportAll);
         }
         eleForm.action = "doExportExcel.action";
         eleForm.submit();
         eleForm.action = lastAction;
         return;
        }else if(dataV == '2'){
            var eleForm = $("pageQueryForm");
         var lastAction = eleForm.action;
         var eleHiddenExportExcel = new Element("input",{type:"hidden",name:"ExportAll"});
         eleHiddenExportExcel.wrap(eleForm);
         eleForm.action = "doExportExcel.action";
         eleForm.submit();
         eleForm.action = lastAction;
         return;
        }
}
}

Action：

两个属性：

String fileNames;
InputStream excelStream;

提供get和set方法

public String doExport() throws TaException{

         String result = "";
 
         User user = (User) this.getSession().get("user");

         if(user != null){

                 String ExportAll = this.getHttpServletRequest().getParameter("ExportAll");

                  List dataList = new ArrayList();
                  if(ExportAll == null){
                          log.debug("导出当前页面内容到excel");
                          this.projectService.queryPageProject(user, pageQueryForm,customDisplayWhere,orderQueryString,orgList);
                         dataList = pageQueryForm.getPageRecordList();
                }else{
                           log.debug("导出所有容到excel");
                          dataList = this.projectService.queryAllProject(user,pageQueryForm,customDisplayWhere,orderQueryString,orgList);
                 }

                 HSSFWorkbook workbook = printExcel(tmpContent,tmpContentCn,dataList);
          
                if(workbook != null){
                       try{
                               Calendar c = Calendar.getInstance();
                              int year = c.get(Calendar.YEAR);
                               int month = c.get(Calendar.MONTH)+1;
                               String month_ = new String(""+month);
                               if(month<10){
                                     month_ = "0"+month;
                               }
                               int day = c.get(Calendar.DAY_OF_MONTH);
                               String day_ = new String(""+day);
                              if(day<10){
                                     day_ = "0"+day;
                                }
                                this.exportExcel(workbook,year+month_+""+day_+"sxta.xls");
                               result = "outExcel";
                         }catch(IOException e){
                               e.printStackTrace();
                               message = "出错了！";
                               redirectTo = this.getHttpServletRequest().getContextPath()+"/task/listProject.action";
                               return SUCCESS;
                         }
                }

        }else{

                 log.debug("user is null");
                message = "出错了！";
                 redirectTo = this.getHttpServletRequest().getContextPath()+"/task/listProject.action";
                 return SUCCESS;

        }

        return result;

}

private HSSFWorkbook printExcel(String tmpContent,String tmpContentCn,List dataList){
 
          HSSFWorkbook workbook = null;
          String[] titles_CN = tmpContentCn.split(",");
          String[] titles_EN = tmpContent.split(",");
          try{
               //创建工作簿实例
                workbook = new HSSFWorkbook();
               //创建工作表实例
              HSSFSheet sheet = workbook.createSheet("sxtaExcel");
               //设置列宽
               this.setSheetColumnWidth(titles_CN,sheet);
             //获取样式
               HSSFCellStyle style = this.createTitleStyle(workbook);
               if(dataList != null){
                    //创建第一行标题
                     HSSFRow row = sheet.createRow((short)0);// 建立新行
                     for(int i=0;i<titles_CN.length;i++){
                     this.createCell(row, i, null, HSSFCell.CELL_TYPE_STRING,
                            this.getText(titles_CN[i]));
                     }
                     //给excel填充数据
                    for(int i=0;i<dataList.size();i++){
                             // 将dataList里面的数据取出来
                             Project project= (Project)dataList.get(i);
                              HSSFRow row1 = sheet.createRow((short) (i + 1));// 建立新行
                  
                             boolean isOverTime = false;
                              for(int j=0;j<titles_EN.length;j++){
                                       String tmpstr = "";
                                       if (titles_EN[j].equals("name")){
                                             this.createCell(row1, j, style, HSSFCell.CELL_TYPE_STRING,
                               project.getName());
                                       }    

                                      ……             

                           }
                 
                   }
            }else{
                     this.createCell(sheet.createRow(0), 0, style,HSSFCell.CELL_TYPE_STRING, "查无资料");
            }
       }catch(Exception e){
                   e.printStackTrace();
       }
      return workbook;
}

//设置列宽
private void setSheetColumnWidth(String[] titles_CN,HSSFSheet sheet){
        // 根据你数据里面的记录有多少列，就设置多少列
       for(int i=0;i<titles_CN.length;i++){
               sheet.setColumnWidth((short)i, (short) 3000);
       }

}

//设置excel的title样式 
private HSSFCellStyle createTitleStyle(HSSFWorkbook wb) {
       HSSFFont boldFont = wb.createFont();
       boldFont.setFontHeight((short) 200);
       HSSFCellStyle style = wb.createCellStyle();
       style.setFont(boldFont);
       style.setDataFormat(HSSFDataFormat.getBuiltinFormat("###,##0.00"));
       //style.setFillPattern(HSSFCellStyle.SOLID_FOREGROUND);
       //style.setFillBackgroundColor(HSSFColor.LIGHT_ORANGE.index);
       return style; 
}
   
   
//创建Excel单元格 
private void createCell(HSSFRow row, int column, HSSFCellStyle style,int cellType,Object value) {
       HSSFCell cell = row.createCell((short) column);
       cell.setEncoding(HSSFCell.ENCODING_UTF_16);
       if (style != null) {
            cell.setCellStyle(style);
       } 
       switch(cellType){
            case HSSFCell.CELL_TYPE_BLANK: {} break;
            case HSSFCell.CELL_TYPE_STRING: {cell.setCellValue(value.toString()+"");} break;
            case HSSFCell.CELL_TYPE_NUMERIC: {
            cell.setCellType(HSSFCell.CELL_TYPE_NUMERIC);
                cell.setCellValue(Double.parseDouble(value.toString()));}break;
            default: break;
      } 

}

//写入输入流中

private void exportExcel(HSSFWorkbook workbook,String fileName) throws IOException{
        fileNames = fileName;
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        workbook.write(baos);
        baos.flush();
        byte[] aa = baos.toByteArray();
        excelStream = new ByteArrayInputStream(aa, 0, aa.length);
        baos.close();
}

接下来，struts.xml中的配置：

<result name="outExcel" type="stream">
                     <param name="contentType">application/vnd.ms-excel</param>   <!-- 注意这里的ContentType -->
                     <param name="inputName">excelStream</param>
                     <param name="contentDisposition">attachment;filename="${fileNames}"</param>
                     <param name="bufferSize">1024</param>
</result>


三个jar包：

OK