springboor+vue跳转预览存在sftp服务器中的pdf，不用任何组件

首先，你需要在Spring Boot项目中使用JSch库连接到SFTP服务器，并从服务器上下载PDF文件。以下是一个简单的示例：

import com.jcraft.jsch.*;

import java.io.*;

public class SftpUtil {

    private static final int BUFFER_SIZE = 1024;

    public void downloadFile(String host, int port, String username, String password, String remoteFilePath, String localFilePath) throws JSchException, SftpException, IOException {
        JSch jsch = new JSch();
        Session session = jsch.getSession(username, host, port);
        session.setPassword(password);
        session.setConfig("StrictHostKeyChecking", "no");
        session.connect();

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

        InputStream inputStream = channelSftp.get(remoteFilePath);
        OutputStream outputStream = new FileOutputStream(new File(localFilePath));

        byte[] buffer = new byte[BUFFER_SIZE];
        int bytesRead = -1;
        while ((bytesRead = inputStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, bytesRead);
        }

        outputStream.close();
        inputStream.close();
        channelSftp.disconnect();
        session.disconnect();
    }
}

接下来，在Spring Boot的Controller中处理GET请求，下载PDF并将其写入响应流中以进行预览：

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

import javax.servlet.http.HttpServletResponse;
import java.io.*;

@Controller
public class PdfController {

    private static final String SFTP_HOST = "your_sftp_server_host";
    private static final int SFTP_PORT = 22;
    private static final String SFTP_USERNAME = "your_sftp_username";
    private static final String SFTP_PASSWORD = "your_sftp_password";
    private static final String SFTP_REMOTE_FILE_PATH = "/path/to/your/pdf/file/on/sftp_server";

    @GetMapping("/preview/{filename}")
    public void previewPdf(@PathVariable("filename") String filename, HttpServletResponse response) {
        String localFilePath = "/path/to/local/temporary/file/" + filename;
        try {
            SftpUtil sftpUtil = new SftpUtil();
            sftpUtil.downloadFile(SFTP_HOST, SFTP_PORT, SFTP_USERNAME, SFTP_PASSWORD, SFTP_REMOTE_FILE_PATH, localFilePath);

            File file = new File(localFilePath);
            response.setContentType("application/pdf");
            response.addHeader("Content-Disposition", "inline; filename=" + filename);
            response.setContentLength((int) file.length());

            FileInputStream fileInputStream = new FileInputStream(file);
            OutputStream outputStream = response.getOutputStream();

            byte[] buffer = new byte[BUFFER_SIZE];
            int bytesRead = -1;
            while ((bytesRead = fileInputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }

            fileInputStream.close();
            outputStream.flush();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

最后，在Vue中使用`<embed>`标签来显示PDF文件：

<template>
  <div>
    <embed :src="'/preview/' + filename" type="application/pdf" width="100%" height="600px" />
  </div>
</template>

<script>
export default {
  name: 'PdfPreview',
  props: {
    filename: String
  }
}
</script>

这样，当你在Vue中使用`<pdf-preview>`组件时，它会从SFTP服务器中下载PDF文件并在页面上预览它。