springMVC方法，导出/下载文件。

@RequestMapping(value = "/form/printContract")
public ResponseEntity<byte[]> printContract(ContractIreportForm form)throws Exception {
HttpHeaders headers = new HttpHeaders();

//声明变量
File file = null ;
try {
file = new File("");
String downFileName = new String(("").getBytes("UTF-8"),"iso-8859-1");
headers.setContentDispositionFormData("attachment", downFileName);
headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
form.setIsSuccess(SUCCESS);
} catch (Exception e) {
form.setIsSuccess(FAILURE);
form.setMsg(exMsg(e));
}
return new ResponseEntity<byte[]>(FileUtils.readFileToByteArray(file),
headers, HttpStatus.CREATED);
}