jsch 密钥登录下载sftp文件 代码

可以使用 JSch 库实现 SFTP 文件下载，以下是一个示例代码：

import com.jcraft.jsch.*;

import java.io.*;

public class SFTPDownloader {
    public static void downloadFile(String host, int port, String username, String privateKeyPath, String remoteFilePath, String localFilePath)
            throws JSchException, IOException {
        JSch jsch = new JSch();
        jsch.addIdentity(privateKeyPath);

        Session session = jsch.getSession(username, host, port);
        session.setConfig("StrictHostKeyChecking", "no");
        session.connect();

        ChannelSftp sftpChannel = (ChannelSftp) session.openChannel("sftp");
        sftpChannel.connect();

        InputStream inputStream = null;
        try {
            inputStream = sftpChannel.get(remoteFilePath);
        } catch (SftpException e) {
            throw new RuntimeException("Failed to download remote file: " + remoteFilePath, e);
        }

        OutputStream outputStream = null;
        try {
            outputStream = new FileOutputStream(localFilePath);
            byte[] buffer = new byte[1024];
            int bytesRead = -1;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }
            System.out.println("File downloaded: " + remoteFilePath);
        } catch (IOException e) {
            throw new RuntimeException("Failed to write to local file: " + localFilePath, e);
        } finally {
            if (outputStream != null) {
                try {
                    outputStream.close();
                } catch (IOException e) {
                    // ignore
                }
            }
            if (inputStream != null) {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    // ignore
                }
            }
        }

        sftpChannel.disconnect();
        session.disconnect();
    }
}

其中，`host` 为 SFTP 服务器地址，`port` 为 SFTP 服务器端口号，`username` 为登录用户名，`privateKeyPath` 为私钥文件的路径，`remoteFilePath` 为远程文件路径，`localFilePath` 为本地文件路径。

使用示例：

public static void main(String[] args) throws Exception {
    String host = "sftp.example.com";
    int port = 22;
    String username = "user";
    String privateKeyPath = "/path/to/private/key";
    String remoteFilePath = "/remote/file/path.txt";
    String localFilePath = "/local/file/path.txt";

    SFTPDownloader.downloadFile(host, port, username, privateKeyPath, remoteFilePath, localFilePath);
}

在实际使用时，需要将上述代码中的异常处理逻辑进行修改，以符合实际需求。