[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) {

        }
    }
}