解释这段代码@RequestMapping("/upload") public R upload(@RequestParam("file") MultipartFile file,String type) throws Exception { if (file.isEmpty()) { throw new EIException("上传文件不能为空"); } String fileExt = file.getOriginalFilename().substring(file.getOriginalFilename().lastIndexOf(".")+1); File path = new File(ResourceUtils.getURL("classpath:static").getPath()); if(!path.exists()) { path = new File(""); } File upload = new File(path.getAbsolutePath(),"/upload/"); if(!upload.exists()) { upload.mkdirs(); } String fileName = new Date().getTime()+"."+fileExt; File dest = new File(upload.getAbsolutePath()+"/"+fileName); File resourceFile = new File(path.getAbsolutePath().split("target")[0] +"src\\main\\resources\\static\\upload" + "/" + fileName); byte[] bytes = file.getBytes(); OutputStream out1 = new FileOutputStream(dest); OutputStream out2 = new FileOutputStream(resourceFile); out1.write(bytes); out2.write(bytes); out1.close(); out2.close(); if(StringUtils.isNotBlank(type) && type.equals("1")) { ConfigEntity configEntity = configService.selectOne(new EntityWrapper<ConfigEntity>().eq("name", "faceFile")); if(configEntity==null) { configEntity = new ConfigEntity(); configEntity.setName("faceFile"); configEntity.setValue(fileName); } else { configEntity.setValue(fileName); } configService.insertOrUpdate(configEntity); } return R.ok().put("file", fileName); }

这是一个 Spring Boot 框架中的 Controller 层方法，使用 @RequestMapping 注解指定了请求路径为 "/upload"，接受了两个参数：一个是名为 file 的 Multipart 文件，另一个是名为 type 的字符串参数。该方法的作用是将上传的文件保存到服务器的本地磁盘上，并将文件名返回给前端。

首先，判断上传的文件是否为空，如果为空则抛出异常。然后，获取上传文件的扩展名，并创建一个 File 对象表示静态资源目录。 如果该目录不存在，则将其设置为空。接着，创建一个名为 "upload" 的文件夹（如果不存在），并为上传文件生成一个以时间戳为文件名的唯一标识。然后，将上传的文件写入两个输出流中：一个是 dest 对象表示的文件，另一个是 resourceFile 对象表示的文件。最后，如果 type 参数等于 "1"，则将上传文件名保存到数据库中。最终，将文件名返回给前端。

相关问题

<h1>上传/下载文件</h1> <form method="post" action="/file/upload" enctype="multipart/form-data"> <input type="file" name="file" id="fileInput"/> <input type="submit" value="上传" /> </form> <hr> <form method="post" action="/file/download" > <input type="text" name="fileName" placeholder="请输入文件名" /> <input type="submit" value="下载" id="downloadBtn" /> </form> public class SFTPUtil { private static final String host = "10.60.0.160"; private static final int port = 22; private static final String username = "root"; private static final String password = "Z20"; private static Session session = null; public static void connect() throws Exception { } public static void upload(MultipartFile file, String path, String fileName) throws Exception { } public static boolean download(HttpServletResponse response, String path, String fileName) throws Exception { } @Controller @RequestMapping("/file") public class FileController { private static final String UPLOAD_PATH = "/data/sftp/adtuser1/upload/winbidding/"; private static final String DOWNLOAD_PATH = "/data/sftp/adtuser1/upload/winbidding/"; @PostMapping("/upload") @ResponseBody public ModelAndView upload(@RequestParam("file") MultipartFile file) { } @PostMapping("/download") public ModelAndView download(@RequestParam("fileName") String fileName, HttpServletResponse response) throws Exception { } 数据库有host port username password UPLOAD_PATH DOWNLOAD_PATH csmc字段，把上边写死的改成数据库查询，前台页面增加csmc字段下拉框，根据csmc字段把查出来的配置数据完成上传下载功能，用的mysql数据库，把代码改好写出来

首先需要在数据库中创建一个表，用于存储SFTP连接的相关信息：

CREATE TABLE sftp_config (
  id INT PRIMARY KEY AUTO_INCREMENT,
  csmc VARCHAR(50),
  host VARCHAR(50),
  port INT,
  username VARCHAR(50),
  password VARCHAR(50),
  upload_path VARCHAR(255),
  download_path VARCHAR(255)
);

然后在Spring Boot项目中创建一个SFTPUtil类，用于实现SFTP上传和下载功能：

import com.jcraft.jsch.*;

import org.springframework.web.multipart.MultipartFile;

import java.io.*;
import java.util.Properties;

public class SFTPUtil {

    private String host;
    private int port;
    private String username;
    private String password;
    private String uploadPath;
    private String downloadPath;
    private Session session;

    public SFTPUtil(String host, int port, String username, String password, String uploadPath, String downloadPath) {
        this.host = host;
        this.port = port;
        this.username = username;
        this.password = password;
        this.uploadPath = uploadPath;
        this.downloadPath = downloadPath;
    }

    public void connect() throws Exception {
        JSch jsch = new JSch();
        session = jsch.getSession(username, host, port);
        session.setPassword(password);
        Properties config = new Properties();
        config.put("StrictHostKeyChecking", "no");
        session.setConfig(config);
        session.connect();
    }

    public void upload(MultipartFile file, String fileName) throws Exception {
        ChannelSftp channel = (ChannelSftp) session.openChannel("sftp");
        channel.connect();
        channel.cd(uploadPath);
        InputStream inputStream = file.getInputStream();
        channel.put(inputStream, fileName);
        inputStream.close();
        channel.disconnect();
    }

    public boolean download(HttpServletResponse response, String fileName) throws Exception {
        ChannelSftp channel = (ChannelSftp) session.openChannel("sftp");
        channel.connect();
        channel.cd(downloadPath);
        SftpATTRS attrs = channel.lstat(fileName);
        if (attrs == null) {
            channel.disconnect();
            return false;
        }
        response.setHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
        OutputStream outputStream = response.getOutputStream();
        channel.get(fileName, outputStream);
        outputStream.flush();
        outputStream.close();
        channel.disconnect();
        return true;
    }

}

然后在Spring Boot项目中创建一个FileController类，用于处理文件上传和下载请求：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;

import javax.servlet.http.HttpServletResponse;
import java.util.List;
import java.util.Map;

@Controller
@RequestMapping("/file")
public class FileController {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @PostMapping("/upload")
    @ResponseBody
    public String upload(@RequestParam("file") MultipartFile file, @RequestParam("csmc") String csmc) {
        try {
            // 从数据库中获取SFTP连接配置信息
            String sql = "SELECT * FROM sftp_config WHERE csmc = ?";
            Map<String, Object> map = jdbcTemplate.queryForMap(sql, csmc);
            String host = (String) map.get("host");
            int port = (int) map.get("port");
            String username = (String) map.get("username");
            String password = (String) map.get("password");
            String uploadPath = (String) map.get("upload_path");
            String fileName = file.getOriginalFilename();

            // 使用SFTP上传文件
            SFTPUtil sftpUtil = new SFTPUtil(host, port, username, password, uploadPath, null);
            sftpUtil.connect();
            sftpUtil.upload(file, fileName);

            return "上传成功";
        } catch (Exception e) {
            e.printStackTrace();
            return "上传失败";
        }
    }

    @PostMapping("/download")
    public void download(@RequestParam("fileName") String fileName, @RequestParam("csmc") String csmc, HttpServletResponse response) throws Exception {
        // 从数据库中获取SFTP连接配置信息
        String sql = "SELECT * FROM sftp_config WHERE csmc = ?";
        Map<String, Object> map = jdbcTemplate.queryForMap(sql, csmc);
        String host = (String) map.get("host");
        int port = (int) map.get("port");
        String username = (String) map.get("username");
        String password = (String) map.get("password");
        String downloadPath = (String) map.get("download_path");

        // 使用SFTP下载文件
        SFTPUtil sftpUtil = new SFTPUtil(host, port, username, password, null, downloadPath);
        sftpUtil.connect();
        boolean result = sftpUtil.download(response, fileName);
        if (!result) {
            response.getWriter().write("文件不存在");
        }
    }

    @GetMapping("/csmcList")
    @ResponseBody
    public List<String> getCsmcList() {
        // 从数据库中获取所有的csmc字段
        String sql = "SELECT DISTINCT csmc FROM sftp_config";
        List<String> csmcList = jdbcTemplate.queryForList(sql, String.class);
        return csmcList;
    }

}

最后，在HTML页面中加入下面的代码，即可实现文件上传和下载：

<h1>上传/下载文件</h1>
<form method="post" action="/file/upload" enctype="multipart/form-data">
    <input type="file" name="file" id="fileInput"/>
    <select name="csmc" id="csmcSelect"></select>
    <input type="submit" value="上传"/>
</form>
<hr>
<form method="post" action="/file/download">
    <input type="text" name="fileName" placeholder="请输入文件名"/>
    <select name="csmc" id="csmcSelect"></select>
    <input type="submit" value="下载" id="downloadBtn"/>
</form>
<script>
    // 获取csmc列表
    $.get("/file/csmcList", function (data) {
        var csmcSelect = $("#csmcSelect");
        for (var i = 0; i < data.length; i++) {
            var option = $("<option>").val(data[i]).text(data[i]);
            csmcSelect.append(option);
        }
    });
</script>

/** * 上传文件 */ @RequestMapping("/upload") public R upload(@RequestParam("file") MultipartFile file, String type,HttpServletRequest request) throws Exception { if (file.isEmpty()) { throw new EIException("上传文件不能为空"); } String fileExt = file.getOriginalFilename().substring(file.getOriginalFilename().lastIndexOf(".")+1); String fileName = new Date().getTime()+"."+fileExt; File dest = new File(request.getSession().getServletContext().getRealPath("/upload")+"/"+fileName); file.transferTo(dest); if(StringUtils.isNotBlank(type) && type.equals("1")) { ConfigEntity configEntity = configService.selectOne(new EntityWrapper<ConfigEntity>().eq("name", "faceFile")); if(configEntity==null) { configEntity = new ConfigEntity(); configEntity.setName("faceFile"); configEntity.setValue(fileName); } else { configEntity.setValue(fileName); } configService.insertOrUpdate(configEntity); } return R.ok().put("file", fileName); }

这是一个上传文件的方法，使用了Spring MVC框架。用户可以上传一个文件，其中type参数可选，用于区分不同的上传类型。如果type为1，则会将上传的文件名保存到数据库中。在上传文件时，会判断文件是否为空，如果为空则会抛出EIException异常。上传的文件会被保存到项目的upload文件夹下，文件名会加上当前时间戳和文件扩展名。最后，将上传的文件名作为返回结果。