用于返回excel数据流到客户端，HSSFWorkbook是创建好的excel文件，fileName是返回的文名。
private void responseExcel(HSSFWorkbook wk, String fileName, HttpServletResponse response) {
response.reset();
response.setContentType("Application/vnd.ms-excel;charset=UTF-8");
ServletOutputStream out = null;
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
try {
response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, "utf-8"));
out = response.getOutputStream();
wk.write(outputStream);
byte[] bookByteAry = outputStream.toByteArray();
InputStream in = new ByteArrayInputStream(bookByteAry);
// 读取文件流
int len = 0;
byte[] buffer = new byte[1024 * 10];
while ((len = in.read(buffer)) != -1) {
out.write(buffer, 0, len);
}
out.flush();
} catch (Exception e) {
e.printStackTrace();
}
}
