java ftp大文件上传

Java中可以使用Apache Commons Net库来实现FTP文件上传，对于大文件上传，可以使用分片上传的方式，将文件分成多个小块进行上传，以避免一次性上传大文件时出现的网络传输问题。

具体实现步骤如下：
1. 连接FTP服务器
2. 设置传输模式为二进制传输
3. 将文件分成多个小块
4. 逐个上传小块文件
5. 关闭FTP连接

以下是一个简单的示例代码：

import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import java.io.*;

public class FTPUploader {
    private static final int BUFFER_SIZE = 1024 * 1024; // 每个小块的大小
    private static final String SERVER = "ftp.example.com";
    private static final int PORT = 21;
    private static final String USERNAME = "username";
    private static final String PASSWORD = "password";
    private static final String REMOTE_FILE_PATH = "/remote/path/to/file";
    private static final String LOCAL_FILE_PATH = "/local/path/to/file";

    public static void main(String[] args) {
        FTPClient ftpClient = new FTPClient();
        try {
            ftpClient.connect(SERVER, PORT);
            ftpClient.login(USERNAME, PASSWORD);
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);

            File localFile = new File(LOCAL_FILE_PATH);
            long fileSize = localFile.length();
            long uploadedSize = 0;
            int partNumber = 0;

            try (InputStream inputStream = new FileInputStream(localFile)) {
                byte[] buffer = new byte[BUFFER_SIZE];
                int bytesRead;
                while ((bytesRead = inputStream.read(buffer)) != -1) {
                    partNumber++;
                    String remoteFilePath = REMOTE_FILE_PATH + ".part" + partNumber;
                    ftpClient.storeFile(remoteFilePath, new ByteArrayInputStream(buffer, 0, bytesRead));
                    uploadedSize += bytesRead;
                    System.out.println("Uploaded " + uploadedSize + " bytes of " + fileSize + " bytes");
                }
            }

            ftpClient.rename(REMOTE_FILE_PATH + ".part" + partNumber, REMOTE_FILE_PATH);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                ftpClient.disconnect();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}