java直接输出Excel 页面实现下载

public String excelDomnload() throws Exception{
try{
/*
String path = GlobalKeys.getFunctionConfig("user_attach_save","/opt/tmp/");
RegUser ru = ((RegUserLoginInfo) request.getSession().getAttribute(GlobalKeys.REG_USER_IN_SESSION_NAME)).getRegUser();
String tmpPath = File.separator + "import" + File.separator
+ ru.getName() + File.separator;
File targetFolder = new File(path, tmpPath);//合并两个路经
String fName = request.getParameter("fName");
*/
response.setContentType("application/msexcel;");
response.setHeader("Content-Disposition", new String(("attachment;filename="+"error.xls").getBytes("GB2312"), "UTF-8"));

File f = new File("d:/20121211165820140_err.xls");
//File f = new File(targetFolder.getPath()+File.separator+fName);
FileInputStream in = new FileInputStream(f);
byte b[] = new byte[1024];
int i = 0;
ServletOutputStream out = response.getOutputStream();
while((i=in.read(b))!=	-1){
out.write(b, 0, i);
}
out.flush();
out.close();
in.close();
}catch(Exception e){
e.printStackTrace();
}
return null;
}