使用apache commons net进行ftp传输

apache commons net的maven地址：
http://mvnrepository.com/artifact/commons-net/commons-net/3.6

<!-- https://mvnrepository.com/artifact/commons-net/commons-net -->
<dependency>
    <groupId>commons-net</groupId>
    <artifactId>commons-net</artifactId>
    <version>3.6</version>
</dependency>

apache commons net的说明文档地址：http://commons.apache.org/proper/commons-net/

apache commons net的依赖关系：http://commons.apache.org/proper/commons-net/dependencies.html
看到apache commons net 3.6依赖于junit 4.12。

下面的测试程序用于下载指定位置的ftp上的文件到本地目录：

package test;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

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

public class FTPDataGetter {
    public static final String FTP_SRV_HOSTNAME = "192.168.100.35";
    public static final Integer FTP_SRV_PORT = 21;
    public static final String FTP_SRV_USERNAME = "zifeiy";
    public static final String FTP_SRV_PASSWORD = "password";
    public static final String LOCAL_DIRECTORY = "E:\\report";
    
    private FTPClient ftpClient = null;
    
    public FTPDataGetter() {
        this.ftpClient = new FTPClient();
        ftpClient.setControlEncoding("utf-8");
        try {
            ftpClient.connect(FTP_SRV_HOSTNAME, FTP_SRV_PORT);
            ftpClient.login(FTP_SRV_USERNAME, FTP_SRV_PASSWORD);
            int replyCode = ftpClient.getReplyCode();
            if (FTPReply.isPositiveCompletion(replyCode) == true) {
                // 登陆成功
                System.out.println("FTP connect to " + FTP_SRV_HOSTNAME + ":" + FTP_SRV_PORT + " succeed!");
            }
            else {
                System.out.println("FTP connect to " + FTP_SRV_HOSTNAME + ":" + FTP_SRV_PORT + " failed!");
                this.ftpClient = null;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public void downloadOneDayFiles(String dayString) {
        if (this.ftpClient == null) {
            System.out.println("[ERROR] because ftp client is NULL!");
            return;
        }
        try {
            ftpClient.changeWorkingDirectory("sdata/S-999000");
            // 进入系统文件夹
            for (FTPFile sysFile : this.ftpClient.listDirectories()) {
                String sysName = sysFile.getName();
//              System.out.println("sysName = " + sysName);
                boolean changeSysFlag = ftpClient.changeWorkingDirectory(sysName);
                if (changeSysFlag == true) {
                    // 进入类型文件夹 ADD或者ALL
                    for (FTPFile typeFile : this.ftpClient.listDirectories()) {
                        String typeName = typeFile.getName();
                        boolean changeTypeFlag = ftpClient.changeWorkingDirectory(typeName);
                        if (changeTypeFlag == true) {
                            // 进入当前目录，该目录下应该只有一个文件
                            boolean changeDayFlag = ftpClient.changeWorkingDirectory(dayString);
                            if (changeDayFlag == true) {
                                for (FTPFile needFile : ftpClient.listFiles()) {
                                    System.out.println(needFile.getName());
                                    downloadOneFile(dayString, needFile.getName());
                                }
                                ftpClient.changeToParentDirectory();
                            }
                            ftpClient.changeToParentDirectory();
                        }
                    }
                    ftpClient.changeToParentDirectory();
                }
            }
            
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    private boolean downloadOneFile(String dayString, String filename) {
        if (this.ftpClient == null) {
            return false;
        }
        OutputStream os = null;
        System.out.println("begin download file " + filename + " ...");
        String directoryString = LOCAL_DIRECTORY + File.separator + dayString;
        File directoryFile = new File(directoryString);
        if (directoryFile.exists() == false) {
            directoryFile.mkdirs();
        }
        File localFile = new File(directoryString + File.separator + filename);
        try {
            os = new FileOutputStream(localFile);
            ftpClient.retrieveFile(filename, os);
            os.close();
            System.out.println("download file " + filename + " finished!");
            return true;
        } catch (Exception e) {
            System.out.println("download file " + filename + " failed!");
            e.printStackTrace();
            return false;
        }
    }
    
    public static void main(String[] args) {
        FTPDataGetter ftpDataGetter = new FTPDataGetter();
        for (int year = 2018; year<=2018; year ++) {
            for (int month = 1; month <= 12; month ++) {
                for (int day = 10; day <= 20; day ++) {
                    String dayString = String.format("%d%02d%02d", year, month, day);
                    ftpDataGetter.downloadOneDayFiles(dayString);
                }
            }
        }
//      ftpDataGetter.downloadOneDayFiles("20180502");
    }
}