文件下载啊，

package com.example.filedownload;

import org.springframework.core.io.InputStreamResource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

@RestController
public class FileDownloadController {

@GetMapping("/download")
public ResponseEntity<InputStreamResource> downloadFile(@RequestParam String fileUrl) {
    try {
        URL url = new URL(fileUrl);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");

        int responseCode = connection.getResponseCode();
        if (responseCode == HttpURLConnection.HTTP_OK) { // HTTP OK
            InputStream inputStream = connection.getInputStream();
            String fileName = getFileNameFromUrl(fileUrl);

            HttpHeaders headers = new HttpHeaders();
            headers.add(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=" + fileName);

            return new ResponseEntity<>(new InputStreamResource(inputStream), headers, HttpStatus.OK);
        } else {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }
    } catch (IOException e) {
        e.printStackTrace();
        return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

private String getFileNameFromUrl(String fileUrl) {
    String path = new URL(fileUrl).getPath();
    return path.substring(path.lastIndexOf('/') + 1);
}

}