servlet实现文件的下载

public class DownLoadServlet extends HttpServlet{
public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {
this.doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {

FileInputStream fis=null;
request.setCharacterEncoding("UTF-8");


String fileName = request.getParameter("fileName"); //获取文件名
try{
ServletContext servletContext=this.getServletContext();
String realpath = servletContext.getRealPath("/templates/"); //获取服务器的物理路径
String templateXlsPath = realpath + File.separator + fileName;//获取完整的文件路径

//读取模板
fis = new FileInputStream(templateXlsPath); // 根据excel文件路径创建文件流
response.reset();
response.setContentType("application/vnd.ms-excel;charset=UTF-8");
response.setHeader("Content-Disposition", "attachment; filename=" + java.net.URLEncoder.encode(fileName, "UTF-8"));

ServletOutputStream ouputStream = response.getOutputStream();

byte[] buff = new byte[1024];//设置每次写入缓存大小
//把输出流写入客户端
int readCount = 0;
readCount = fis.read(buff);
while(readCount != -1){
ouputStream.write(buff,0,readCount);
readCount = fis.read(buff);
}
ouputStream.flush();
ouputStream.close();
fis.close();

}catch(Exception e){
String errorMessage = "导出Excel出现异常";
ToftLogger.error(errorMessage + e.getMessage());
}finally{
//变量置空
fis=null;
}
}
}