用apache commons.net做FTP断点继传

package com.bettersoft.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.io.RandomAccessFile;
import java.io.StringWriter;

import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPFile;
import org.apache.commons.net.ftp.FTPReply;

/**
 * FTP上传文件，支持断点续传
 * @author wanglh
 *
 */

public class AppendFtp extends FTPClient {

	/**
	 * 错误日志
	 * @param ae ae
	 */
	public void logException(Exception ae) {
		StringWriter sw = new StringWriter();
		PrintWriter pw = new PrintWriter(sw);
		ae.printStackTrace(pw);
	}
	
	public boolean deleteFile(String pathname) {
		boolean succ = false;
		try {
			succ = ftp.deleteFile(pathname);
		} catch (IOException e) {
			e.printStackTrace();
		}
		return succ;
	}

	public FTPFile[] listFiles(String remote) throws IOException {
		if(remote != null && !"".equals(remote.trim())) {
			ftp.changeWorkingDirectory(remote); // 进入ftp目录
		}
		return ftp.listFiles();
	}
	
	
	/**
	 * 上传文件
	 * @param remote，远程路径
	 * @param local 本地全路径
	 * @return 是否成功
	 * @throws IOException IOException
	 */
	public boolean upload(String remote, String local)
			throws IOException {
		String temp[] = local.replaceAll("\\\\","/").split("/");//取文件名
		String fileName = "";
		if(temp.length > 1){
		    fileName = temp[temp.length - 1];
		}
		ftp.enterLocalPassiveMode();
		ftp.setFileType(FTPClient.BINARY_FILE_TYPE); // 2进制文件时,防止文件损坏
		boolean result;
		if(remote != null && !"".equals(remote.trim())) {
			ftp.changeWorkingDirectory(remote); // 进入ftp目录
		}
		boolean isExists = false;
		long fileSize = 123;
		FTPFile[] files = ftp.listFiles();
		for (int i = 0; i < files.length; i++) {
			FTPFile file = files[i];
			if (fileName.equals(file.getName())) {
				isExists = true;
				fileSize = file.getSize();
				break;
			}
		}
		if (isExists) {
			// 文件存在时, 使用断点上传方式
			File fLocal = new File(local);
			OutputStream os = ftp.appendFileStream(fileName);
			RandomAccessFile randomAccessFileLocal = new RandomAccessFile(
					fLocal, "r");
			randomAccessFileLocal.seek(fileSize);
			int len = 0;
			byte[] bt = new byte[1024];
			while ((len = randomAccessFileLocal.read(bt)) > 0) {
				os.write(bt, 0, len);
			}
			randomAccessFileLocal.close();
			os.close();
			result = true;
			ftp.completePendingCommand();
		} else {
			// 不存在时, 直接上传
			File f = new File(local);
			FileInputStream in = new FileInputStream(f);
			result = ftp.storeFile(fileName, in);
			in.close();
		}
		return result;
	}

	/**
	 * 建立FTP连接
	 * @param hostname FTP主机名
	 * @param port 端口
	 * @param username 用户名
	 * @param password 密码
	 * @return 是否连接成功
	 * @throws IOException IOException
	 */
	public boolean connect(String hostname, int port, String username,
			String password) throws IOException {
		ftp = new FTPClient();
		ftp.connect(hostname, port);
		ftp.login(username, password);
		if (!FTPReply.isPositiveCompletion(ftp.getReplyCode())) {
			disconnect();
			return false;
		}
		return true;
	}

	/**
	 * 关闭FTP连接
	 */
	public void disconnect() throws IOException {
		if (ftp.isConnected()) {
			ftp.disconnect();
		}
	}

	public FTPClient ftp;

	public static void main(String[] args) {
		try {
			AppendFtp ftpClient = new AppendFtp();
			ftpClient.connect("127.0.0.1", 21, "refar", "refar123");
			ftpClient.deleteFile("/sss/abc.txt");
			ftpClient.disconnect();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

 网上拷贝的代码，但网上的断点续传有问题，没有ftp.completePendingCommand();