获取webroot下的文件

public static void downloadFile(String filePath, javax.servlet.http.HttpServletResponse response) {
  String fileName = ""; //文件名，输出到用户的下载对话框
  //从文件完整路径中提取文件名，并进行编码转换，防止不能正确显示中文名
  try {
   if (filePath.lastIndexOf("/") > 0) {
    fileName = new String(filePath.substring(filePath.lastIndexOf("/") + 1, filePath.length()).getBytes(
      "GB2312"), "ISO8859_1");
   } else if (filePath.lastIndexOf("\\") > 0) {
    fileName = new String(filePath.substring(filePath.lastIndexOf("\\") + 1, filePath.length()).getBytes(
      "GB2312"), "ISO8859_1");
   }
  } catch (Exception e) {
  }
  //打开指定文件的流信息
  FileInputStream fs = null;
  try {
   fs = new FileInputStream(new File(filePath));
  } catch (FileNotFoundException e) {
   e.printStackTrace();
   return;
  }
  //设置响应头和保存文件名
  response.setContentType("APPLICATION/OCTET-STREAM");
  response.setHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
  //写出流信息
  int b = 0;
  try {
   PrintWriter out = response.getWriter();
   while ((b = fs.read()) != -1) {
    out.write(b);
   }
   fs.close();
   out.close();
   System.out.println("文件下载完毕.");
  } catch (Exception e) {
   e.printStackTrace();
   System.out.println("下载文件失败!");
  }
 }