JAVA FTP上传下载文件

在Java中，通过Java的FTP客户端库，如Apache Commons Net，你可以方便地进行FTP文件的上传和下载操作。以下是基本步骤：

**上传文件（PUT）：**

import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;

public void uploadFile(String host, int port, String username, String password, String remoteFilePath, File localFile) {
    FTPClient ftpClient = new FTPClient();
    try {
        ftpClient.connect(host, port);
        ftpClient.login(username, password);
        ftpClient.setFileType(FTP.BINARY_FILE_TYPE); // 设置二进制模式

        // 上传文件到服务器
        boolean uploaded = ftpClient.storeFile(remoteFilePath, new FileInputStream(localFile));
        if (uploaded) {
            System.out.println("文件 " + localFile.getName() + " 已成功上传至 " + remoteFilePath);
        } else {
            System.err.println("上传文件失败");
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            ftpClient.logout();
            ftpClient.disconnect();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

**下载文件（GET）：**

import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;

public void downloadFile(String host, int port, String username, String password, String remoteFilePath, File localDestination) {
    FTPClient ftpClient = new FTPClient();
    try {
        ftpClient.connect(host, port);
        ftpClient.login(username, password);

        // 检查文件是否存在
        boolean fileExists = ftpClient.getFileList().stream()
                .anyMatch(file -> file.getName().equals(remoteFilePath));

        if (!fileExists) {
            System.err.println("文件 " + remoteFilePath + " 不存在");
            return;
        }

        ftpClient.enterLocalPassiveMode(); // 对于大型文件，启用被动模式避免防火墙问题
        boolean downloaded = ftpClient.retrieveFile(remoteFilePath, new FileOutputStream(localDestination));
        if (downloaded) {
            System.out.println("文件 " + remoteFilePath + " 已成功下载至 " + localDestination.getAbsolutePath());
        } else {
            System.err.println("下载文件失败");
        }
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        try {
            ftpClient.logout();
            ftpClient.disconnect();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}