Java code implements FTP server to upload files and download files

1. Explanation

To implement ftp in Java, you need to rely on the commons-net-3.3.jar package. First download the jar package. This thing is packaged and you can use it directly. Standing on the shoulders of giants to see the problem, you can also write the internal implementation by hand. . Commons-net-3.3.jar package download address http://download.csdn.net/download/qq_31634461/10034989

1.ftp upload and download tools

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPFile;
import org.apache.commons.net.ftp.FTPReply;

/**
 * ftp上传下载工具类
 */
public class FtpUtil {
    
    

    /** 
     * Description: 向FTP服务器上传文件 
     * @param host FTP服务器hostname 
     * @param port FTP服务器端口 
     * @param username FTP登录账号 
     * @param password FTP登录密码 
     * @param basePath FTP服务器基础目录
     * @param filePath FTP服务器文件存放路径。例如分日期存放：/2015/01/01。文件的路径为basePath+filePath
     * @param filename 上传到FTP服务器上的文件名 
     * @param input 输入流 
     * @return 成功返回true，否则返回false 
     */  
    public static boolean uploadFile(String host, int port, String username, String password, String basePath,
            String filePath, String filename, InputStream input) {
        boolean result = false;
        FTPClient ftp = new FTPClient();
        try {
            int reply;
            ftp.connect(host, port);// 连接FTP服务器
            // 如果采用默认端口，可以使用ftp.connect(host)的方式直接连接FTP服务器
            ftp.login(username, password);// 登录
            reply = ftp.getReplyCode();
            if (!FTPReply.isPositiveCompletion(reply)) {
                ftp.disconnect();
                return result;
            }
            //切换到上传目录
            if (!ftp.changeWorkingDirectory(basePath+filePath)) {
                //如果目录不存在创建目录
                String[] dirs = filePath.split("/");
                String tempPath = basePath;
                for (String dir : dirs) {
                    if (null == dir || "".equals(dir)) continue;
                    tempPath += "/" + dir;
                    if (!ftp.changeWorkingDirectory(tempPath)) {
                        if (!ftp.makeDirectory(tempPath)) {
                            return result;
                        } else {
                            ftp.changeWorkingDirectory(tempPath);
                        }
                    }
                }
            }
             ftp.enterLocalPassiveMode();  
            //设置上传文件的类型为二进制类型
            ftp.setFileType(FTP.BINARY_FILE_TYPE);
            //上传文件
            if (!ftp.storeFile(filename, input)) {
                return result;
            }
            input.close();
            ftp.logout();
            result = true;
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (ftp.isConnected()) {
                try {
                    ftp.disconnect();
                } catch (IOException ioe) {
                }
            }
        }
        return result;
    }

//---------------测试--------------信息自己填写 
    public static void main(String[] args) {
        try {  
            FileInputStream in=new FileInputStream(new File("E:\\5.jpg"));  
            boolean flag = uploadFile("IP地址", 21, "用户名", "密码", "home/www/images","/2017/10/21", "1.jpg", in);  
            System.out.println(flag);  
        } catch (FileNotFoundException e) {  
            e.printStackTrace();  
        }  
    }
}

2. Download tools

/** 
     * Description: 从FTP服务器下载文件 
     * @param host FTP服务器hostname 
     * @param port FTP服务器端口 
     * @param username FTP登录账号 
     * @param password FTP登录密码 
     * @param remotePath FTP服务器上的相对路径 
     * @param fileName 要下载的文件名 
     * @param localPath 下载后保存到本地的路径 
     * @return 
     */  
    public static boolean downloadFile(String host, int port, String username, String password, String remotePath,
            String fileName, String localPath) {
        boolean result = false;
        FTPClient ftp = new FTPClient();
        try {
            int reply;
            ftp.connect(host, port);
            // 如果采用默认端口，可以使用ftp.connect(host)的方式直接连接FTP服务器
            ftp.login(username, password);// 登录
            reply = ftp.getReplyCode();
            if (!FTPReply.isPositiveCompletion(reply)) {
                ftp.disconnect();
                return result;
            }
            ftp.changeWorkingDirectory(remotePath);// 转移到FTP服务器目录
            FTPFile[] fs = ftp.listFiles();
            for (FTPFile ff : fs) {
                if (ff.getName().equals(fileName)) {
                    File localFile = new File(localPath + "/" + ff.getName());

                    OutputStream is = new FileOutputStream(localFile);
                    ftp.retrieveFile(ff.getName(), is);
                    is.close();
                }
            }

            ftp.logout();
            result = true;
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            if (ftp.isConnected()) {
                try {
                    ftp.disconnect();
                } catch (IOException ioe) {
                }
            }
        }
        return result;
    }

2. Problem Analysis

1. If the connection is unsuccessful and the file cannot be created

Firewall, problem, whether to open port 21, and whether there is enough authority, assign 777 authority

2. The connection is successful, the file can be created, but the file cannot be uploaded

Add a line to the code

FTPClient.enterLocalPassiveMode();

This method means that before each data connection, the ftp client tells the ftp server to open a port to transmit data.

3. After uploading the file, it is found that the file is garbled

Transmission format problem, add a line to the codeftpClient.setFileType(FTP.BINARY_FILE_TYPE);//设置上传格式

4. Reprinting is prohibited without my consent