关于springmvc+ibatis使用poi导出Excel的有关问题

@org.springframework.stereotype.Controller(value = "interviewLogController")

@Scope(value = "prototype")
public class InterviewLogController implements Controller {

	@Resource(name="InterviewLogBiz")
	private InterviewLogBiz interviewLogBiz;
	 
	@RequestMapping(value = "ExportInterviewLogQuery2")
	public void exportInterviewExcel2(HttpServletRequest req,
			HttpServletResponse resp) throws Exception {
		Interview interview = new Interview();
		//File file = new File(getServletContext().getRealPath("WEB-INF/book.jpg"));
        resp.setContentType("octets/stream");
        resp.addHeader("Content-Disposition",
                "attachment;filename=学员访谈记录表.xls");
        ExportExcel<Interview> ex = new ExportExcel<Interview>();
        //ExportExcel<T> ex = new ExportExcel<T>();
        //创建列
        String[] headers = { "姓名", "访谈时间", "电话或当面访谈内容", "备注" };
        //从数据库中读取数据
        List<Interview> dataset = new ArrayList<Interview>();
        String csid = req.getParameter("csid");
		interview.setCsid(csid);
		if(csid!=null && csid!=""){
			dataset = interviewLogBiz.query(interview.getCsid());
			interview.setName(dataset.get(0).getName());
			interview.setIinterviewTime(dataset.get(0).getIinterviewTime());
			interview.setIcontent(dataset.get(0).getIcontent());
			interview.setInterviewWay(dataset.get(0).getInterviewWay());
		}else{
			return ;
		}
        try {
            
            dataset.add(new Interview(interview.getName(), interview.getIinterviewTime(),
            		interview.getIcontent(), interview.getInterviewWay()));
           
            OutputStream out = resp.getOutputStream();
            ex.exportExcel(headers, dataset, out);
            out.close();
            System.out.println("excel导出成功！");
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (Exception e) {
			// TODO: handle exception
        	e.printStackTrace();
		}
	}
}

package com.it94hao.util;
public class ExportExcel<T> {
    public void exportExcel(String[] headers, Collection<T> dataset,
            OutputStream out) {
        exportExcel("测试POI导出EXCEL文档", headers, dataset, out, "yyyy-MM-dd");
    }
    
    @SuppressWarnings("unchecked")
    public void exportExcel(String title, String[] headers,
            Collection<T> dataset, OutputStream out, String pattern) {
        // 声明一个工作薄
        HSSFWorkbook workbook = new HSSFWorkbook();
        // 生成一个表格
        HSSFSheet sheet = workbook.createSheet(title);
        // 设置表格默认列宽度为15个字节
        sheet.setDefaultColumnWidth((short) 15);
        // 生成一个样式
        HSSFCellStyle style = workbook.createCellStyle();
        // 设置这些样式
        style.setFillForegroundColor(HSSFColor.SKY_BLUE.index);