上面那段代码需要修改 如果服务器中的jar包存在，需要先备份再删除

好的，您可以使用以下代码实现：

import com.jcraft.jsch.*;
import java.io.*;

public class SFTPUploader {

    public static void main(String[] args) {
        String user = "username";
        String password = "password";
        String host = "hostname";
        int port = 22;
        String jarFilePath = "/local/path/to/jar/file.jar";
        String templateFolderPath = "/local/path/to/template/folder";
        String remoteJarFilePath = "/remote/path/to/jar/file.jar";
        String remoteTemplateFolderPath = "/remote/path/to/template/folder";

        try {
            JSch jsch = new JSch();
            Session session = jsch.getSession(user, host, port);
            session.setPassword(password);
            session.setConfig("StrictHostKeyChecking", "no");
            session.connect();

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

            // Backup and delete the existing jar file if it exists
            if (channelSftp.stat(remoteJarFilePath) != null) {
                String backupJarFilePath = remoteJarFilePath + ".bak";
                channelSftp.rename(remoteJarFilePath, backupJarFilePath);
                System.out.println("Backed up existing jar file to " + backupJarFilePath);
            }

            // Upload the new jar file
            File jarFile = new File(jarFilePath);
            if (jarFile.exists()) {
                channelSftp.put(jarFilePath, remoteJarFilePath);
                System.out.println("Uploaded new jar file to " + remoteJarFilePath);
            } else {
                System.out.println("Jar file not found at " + jarFilePath);
            }

            // Upload the template files
            File templateFolder = new File(templateFolderPath);
            if (templateFolder.exists() && templateFolder.isDirectory()) {
                File[] templateFiles = templateFolder.listFiles();
                for (File templateFile : templateFiles) {
                    if (templateFile.isFile()) {
                        channelSftp.put(templateFile.getAbsolutePath(), remoteTemplateFolderPath + "/" + templateFile.getName());
                    }
                }
                System.out.println("Uploaded template files to " + remoteTemplateFolderPath);
            } else {
                System.out.println("Template folder not found at " + templateFolderPath);
            }

            channelSftp.disconnect();
            session.disconnect();
        } catch (JSchException | SftpException e) {
            e.printStackTrace();
        }
    }
}

在原来的基础上，增加了以下代码：

// Backup and delete the existing jar file if it exists
if (channelSftp.stat(remoteJarFilePath) != null) {
    String backupJarFilePath = remoteJarFilePath + ".bak";
    channelSftp.rename(remoteJarFilePath, backupJarFilePath);
    System.out.println("Backed up existing jar file to " + backupJarFilePath);
}

该代码用于备份并删除服务器上已有的 jar 文件，如果服务器上不存在该文件，则不进行操作。如果您不需要备份文件，可以直接使用以下代码删除文件：

// Delete the existing jar file if it exists
if (channelSftp.stat(remoteJarFilePath) != null) {
    channelSftp.rm(remoteJarFilePath);
    System.out.println("Deleted existing jar file at " + remoteJarFilePath);
}