使用 NIO 實現的一個超級快的 FileServlet

 
private void output(HttpServletResponse response, String filePathAndFileName, String mimeType)
      throws IOException {


File file = new File(filePathAndFileName);

// set response headers
response.setContentType((mimeType != null) ? mimeType : "application/octet-stream");
response.setContentLength((int) file.length());



// read and write file
ServletOutputStream op = response.getOutputStream();
// 128 KB buffer
int bufferSize = 131072;
FileInputStream fileInputStream = new FileInputStream(file);
FileChannel fileChannel = fileInputStream.getChannel();
// 6x128 KB = 768KB byte buffer
ByteBuffer bb = ByteBuffer.allocateDirect(786432);
byte[] barray = new byte[bufferSize];
int nRead, nGet;

try {
  while ((nRead = fileChannel.read(bb)) != -1) {
    if (nRead == 0)
      continue;
    bb.position(0);
    bb.limit(nRead);
    while (bb.hasRemaining()) {
      nGet = Math.min(bb.remaining(), bufferSize);
      // read bytes from disk
      bb.get(barray, 0, nGet);
      // write bytes to output
      op.write(barray);
    }
    bb.clear();
  }
} catch (IOException e) {
  e.printStackTrace();
} finally {
  bb.clear();
  fileChannel.close();
  fileInputStream.close();
}

}
</pre>