使用jxl.jar将html中的表格导出为Excel形式，后台内容已取得，但下载下来的excel表为空是怎么回事？

[晴儿2014]

后台代码

@RequestMapping(value = "/excel")
	private void excel(HttpServletRequest request, HttpServletResponse response) 
	throws IOException{
		request.setCharacterEncoding("UTF-8");
		String content = request.getParameter("c");
		if(content == null){
			Writer out = response.getWriter();
			response.setCharacterEncoding("UTF-8");
			out.write("No Content");
			return;
		}
		try{
			export(content,response);
		}catch(Exception ex){
			ex.printStackTrace();
		}
	}

	private void export(String content, HttpServletResponse response) throws
	IOException,RowsExceededException,WriteException {
		response.setContentType("application/ms-excel");
		String sheetName = getCaption(content);
		if(sheetName == null){
			sheetName = "Sheet1";
		}
		sheetName = sheetName.replaceAll(":", "").replaceAll("[)]", "").replaceAll("[(]", "");
		response.addHeader("Content-Disposition", "attachment; filename=" + new String(sheetName.getBytes("UTF-8"),"ISO-8859-1")+".xls");
		OutputStream os = response.getOutputStream();
		WritableWorkbook wwb = Workbook.createWorkbook(os);
		wwb.setProtected(true);
		WritableSheet sheet = wwb.createSheet(sheetName, 0);
		int row = 0;
		int col = 0;
		Label label = null;
		if(sheetName.trim().length() > 30){
			label = new Label(col,row,sheetName);
			sheet.addCell(label);
			row++;
		}
		List<TD> listBody = getContent(content);
	Map  map = new HashMap();
		for(TD td: listBody){
			if(td == null){
				row ++;
				col = 0;
				continue;
			}
			while (map.get(col + "-" + row) != null){
				col++;
			}
			if(td.colspan >1 || td.rowspan >1){
				sheet.mergeCells(col, row, col+ td.colspan-1, row+td.rowspan-1);
				for(int i=col;i<=col+td.colspan-1;i++){
					for(int j=row;j<=row+td.rowspan-1;j++){
						map.put(i + "-" +j ,true);
				}
			}
		}
		label = new Label(col,row,td.content);
		sheet.addCell(label);
		map.put(col + "-"+row,true);
		col += td.colspan;
		}
		wwb.write();
		wwb.close();
		}
	private String getCaption(String content){
		int begin = content.indexOf("<caption"); int end= content.indexOf("</caption>");
		//int begin = content.indexOf("");
		//int end = content.indexOf("");
		if(begin == -1|| end == -1){
			return null;
		}
		begin = content.indexOf(">", begin);
		if(begin == -1){
			return null;
		}
		return content.substring(begin+1, end);
		
	}
	public List<TD> getContent(String content)throws UnsupportedEncodingException{
		int begin = -1;
		int end = -1;
		int index = -1;
		String numberStr;
		int number;
		String[] tables = content.split("</table>");
		List<TD> list = new ArrayList<TD>();
		for(String table:tables){
			String[] trs = table.split("</tr>");
			for(String tr : trs){
				number = 1;
				String[] ss = tr.split("</td>");
				for(String s : ss){
					begin = s.indexOf("<td"); 
					if(begin== -1)
					{continue;}
					s=s.substring(begin+3); 
					index=s.indexOf(">");
					TD td = new TD();
					begin = s.indexOf("rowSpan=");
					if(begin != -1){
						end = s.indexOf("",begin);
						if(end == -1){
							end = index;
						}
						numberStr = s.substring(begin+8, end).replace('"', ' ').replace('\'', ' ').trim();
						number = Integer.parseInt(numberStr);
						td.rowspan = number;
					}
					begin = s.indexOf("colSpan=");
					if(begin != -1){
						end = s.indexOf("", begin);
						index = s.indexOf(">", begin);
						if(end == -1){
							end = index;
						}
						if(end > index){
							end = index;
						}
						numberStr = s.substring(begin+8, end).replace('"', ' ').replace('\'', ' ').trim();
						number = Integer.parseInt(numberStr);
						td.colspan = number;
					}
					td.content = s.substring(index+1).replaceAll("<.*?> ", "").replaceAll("", "").trim();
					list.add(td);
				}
				list.add(null);
			}
			list.add(null);
			list.add(null);
		}
		return list;
	}
	public class TD {
		 int rowspan = 1;
		 int colspan = 1;
	    String content;
	}

前台代码：
<script type="text/javascript">
function exportExcel(id){
var forum = document.forms["ExcelExportor"];
forum.c.value = eval(id+".innerHTML");
forum.submit();
}
</script>
<table border="1" id="MAIN_TABLE" class="altrowstable" style="width: 20em">
<tbody>
<tr><td>111111</td>
<td>222222</td>
</tr>
</tbody>
</table>
<form action="/repairs/excel" name="ExcelExportor" method="post">
<input type="hidden" name="c">
<input class='btn-style-02' type="button" value="导出Excel" onclick="exportExcel('MAIN_TABLE')">
</form>