[Java] 使用 Apache的 Commons-net库 实现FTP操作

因为最近工作中需要用到FTP操作，而手上又没有现成的FTP代码。就去网上找了一下，发现大家都使用Apache的 Commons-net库中的FTPClient。

但是，感觉用起来不太方便。又在网上找到了很多封装过的。觉得也不是很好用。于是就自己写了一个。网上大多是例子都是直接对文件进行操作，而我更需要的是读到内存，或者从内存上写。并且有很多实用单例模式，但是我觉得如果调用比较多的话，可能会出现问题。

 package com.best.oasis.util.helper;
 
 /**
  * 封装了一些FTP操作
  * Created by bl05973 on 2016/3/11.
  */
 
 import java.io.BufferedReader;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.io.OutputStream;
 import java.io.OutputStreamWriter;
 import java.util.ArrayList;
 import java.util.List;
 
 import org.apache.commons.net.ftp.FTP;
 import org.apache.commons.net.ftp.FTPClient;
 import org.apache.commons.net.ftp.FTPCmd;
 import org.apache.commons.net.ftp.FTPFile;
 import org.apache.commons.net.ftp.FTPReply;
 import org.apache.log4j.Logger;
 
 public class FTPUtil {
     private static Logger logger = Logger.getLogger(FTPUtil.class);
 
     private static FTPClient getConnection() {
         FTPClient client = new FTPClient();
         client.setControlEncoding("UTF-8");
         client.setDataTimeout(30000);
         client.setDefaultTimeout(30000);
         return client;
     }
 
     public static FTPClient getConnection(String host) throws IOException {
         FTPClient client = getConnection();
         client.connect(host);
         if (!FTPReply.isPositiveCompletion(client.getReplyCode())) {
             throw new IOException("connect error");
         }
         return client;
     }
     public static FTPClient getConnection(String host, int port) throws IOException {
         FTPClient client = getConnection();
         client.connect(host, port);
         if (!FTPReply.isPositiveCompletion(client.getReplyCode())) {
             throw new IOException("connect error");
         }
         return client;
     }
 
     public static FTPClient getConnection(String host, String username, String password) throws
             IOException {
         FTPClient client= getConnection(host);
         if (StringUtil.isNotBlank(username)) {
             client.login(username, password);
         }
         //if (!FTPReply.isPositiveCompletion(client.getReplyCode())) {
         //    throw new IOException("login error");
         //}
         return client;
     }
 
     public static FTPClient getConnection(String host, int port, String username, String password)
             throws IOException {
         FTPClient client = getConnection(host, port);
         if (StringUtil.isNotBlank(username)) {
             client.login(username, password);
         }
         //if (!FTPReply.isPositiveCompletion(client.getReplyCode())) {
         //    throw new IOException("login error");
         //}
         return client;
     }
 
     /**
      * 移动文件(若目标文件存在则不移动，并返回false)
      */
     public static boolean moveFile(String curFileName, String targetFileName, FTPClient client)
             throws IOException {
         int reply;
         reply = client.sendCommand(FTPCmd.RNFR, curFileName);
         if (FTPReply.isNegativePermanent(reply)) {
             //logger.error("FTP move file error. code:" + reply);
             System.out.println("FTP move file error. code:" + reply);
             return false;
         }
         reply = client.sendCommand(FTPCmd.RNTO, targetFileName);
         if (FTPReply.isNegativePermanent(reply)) {
             //logger.error("FTP move file error. code:" + reply);
             System.out.println("FTP move file error. code:" + reply);
             return false;
         }
         return true;
     }
 
     /**
      * 读取文件列表
      */
     public static List<String> getFileNameList(FTPClient client) throws IOException {
         FTPFile[] files = client.listFiles();
         List<String> fileNameList = new ArrayList<>();
         for (FTPFile file : files) {
             if (file.isFile()) {
                 fileNameList.add(file.getName());
             }
         }
         if (!FTPReply.isPositiveCompletion(client.getReplyCode())) {
             throw new IOException("get file name list error");
         }
         return fileNameList;
     }
 
     /**
      * 读文件
      */
     public static String readFile(String path, FTPClient client) throws IOException {
         client.setFileType(FTP.EBCDIC_FILE_TYPE);
         InputStream is = client.retrieveFileStream(path);
         if (is == null) {
             return null;
         }
         BufferedReader bf = new BufferedReader(new InputStreamReader(is, "UTF-8"));
         StringBuilder sb = new StringBuilder();
         String str;
         while ((str = bf.readLine()) != null) {
             sb.append(str).append("\n");
         }
         bf.close();
         client.completePendingCommand();
         if (!FTPReply.isPositiveCompletion(client.getReplyCode())) {
             throw new IOException("Remote file net closed success");
         }
         return sb.toString();
     }
 
     @Deprecated
     static boolean downFile(String remotePath, String localPath, FTPClient client)
             throws IOException {
         FileOutputStream fos = new FileOutputStream(localPath);
         client.setFileType(FTPClient.BINARY_FILE_TYPE);
         client.retrieveFile(remotePath, fos);
         client.completePendingCommand();
         if (!FTPReply.isPositiveCompletion(client.getReplyCode())) {
             throw new IOException("Remote file net closed success");
         }
         return false;
     }
 
     /**
      * 写文件
      */
     public static boolean storeAsFile(String context, String remotePath, FTPClient client)
             throws IOException {
         OutputStream out = client.storeFileStream(remotePath);
         OutputStreamWriter writer = new OutputStreamWriter(out, "UTF-8");
         writer.write(context);
         writer.flush();
         writer.close();
         return true;
     }
 
     public static void close(FTPClient client) {
         try {
             if (client != null) {
                 client.disconnect();
             }
         } catch (IOException e) {
 
         }
     }
 }

FTPUtil