读写文件的几种方法（从本地读取到服务器）_如何读取本地文件到服务器-优快云博客

本文介绍了三种文件复制的方法：使用BufferedReader和BufferedWriter进行字符级别的复制；利用FileInputStream和FileOutputStream进行字节级别的复制；通过FileChannel实现高效的大文件复制。

1、用BufferReader和BufferWriter

String fromFile = "D:/images/test.jpg";
  String toFile = signid + "" + count + fromFile.substring(fromFile.lastIndexOf("."),fromFile.length());
  String filePath = session.getServletContext().getRealPath("/") + "email/mailinfo/images/";
  try{
  BufferedReader readChar = new BufferedReader(new FileReader(fromFile));
  BufferedWriter buffer=new BufferedWriter(new FileWriter(filePath + toFile));
  String line = "";
  while((line = readChar.readLine()) != null){
   buffer.write((line + "/n").toCharArray());
   System.out.println(line);
   buffer.flush();
  }
  readChar.close();
  buffer.close();
  }catch(Exception e){
   e.printStackTrace();
  }

2、用FileInputStream和FileOutputStream

  FileInputStream input = new FileInputStream(new File(fromFile));
    FileOutputStream output = new FileOutputStream(
            new File(filePath + toFile));
    int b;
    while (true) {
      byte[] buffer = {};
        if (input.available() < 1024) {
             while ((b = input.read()) != -1) {
                output.write(b);
            }
            break;
        } else {
            input.read(buffer);
            output.write(buffer);
        }
    }
    input.close();
    output.close();

3、用FileChannel（要引入java.nio.channels包）
  FileInputStream input = new FileInputStream(fromFile);
  FileOutputStream output = new FileOutputStream(filePath + toFile);
  FileChannel infileChannel = input.getChannel();
  FileChannel outfileChannel = output.getChannel();
  long size = infileChannel.size();
  infileChannel.transferTo(0, size, (WritableByteChannel)outfileChannel);