如何在Java中实现高效率的文件上传和下载

package cn.juwatech.servlet;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.StandardCopyOption;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
@WebServlet("/upload")
@MultipartConfig
public class FileUploadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String uploadDir = "/path/to/upload/directory";
        Files.createDirectories(Paths.get(uploadDir));
        Part filePart = request.getPart("file");
        String fileName = Paths.get(filePart.getSubmittedFileName()).getFileName().toString();
        File file = new File(uploadDir + File.separator + fileName);
        try (InputStream fileContent = filePart.getInputStream()) {
            Files.copy(fileContent, file.toPath(), StandardCopyOption.REPLACE_EXISTING);
        }
        response.getWriter().println("File " + fileName + " uploaded successfully!");
    }
}

package cn.juwatech.controller;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.mvc.support.RedirectAttributes;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
@Controller
public class FileUploadController {
    private static final String UPLOAD_FOLDER = "/path/to/upload/directory/";
    @PostMapping("/upload")
    public String handleFileUpload(@RequestParam("file") MultipartFile file,
                                   RedirectAttributes redirectAttributes) {
        if (file.isEmpty()) {
            redirectAttributes.addFlashAttribute("message", "Please select a file to upload");
            return "redirect:/uploadStatus";
        }
        try {
            byte[] bytes = file.getBytes();
            Path path = Paths.get(UPLOAD_FOLDER + file.getOriginalFilename());
            Files.write(path, bytes);
            redirectAttributes.addFlashAttribute("message",
                    "You successfully uploaded '" + file.getOriginalFilename() + "'");
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "redirect:/uploadStatus";
    }
}

package cn.juwatech.servlet;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
@WebServlet("/download")
public class FileDownloadServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        String filePath = "/path/to/file/download.txt";
        File downloadFile = new File(filePath);
        if (downloadFile.exists()) {
            response.setContentType("application/octet-stream");
            response.setContentLengthLong(downloadFile.length());
            response.setHeader("Content-Disposition", "attachment; filename=\"" + downloadFile.getName() + "\"");
            try (BufferedInputStream in = new BufferedInputStream(new FileInputStream(downloadFile));
                 BufferedOutputStream out = new BufferedOutputStream(response.getOutputStream())) {
                byte[] buffer = new byte[1024];
                int bytesRead;
                while ((bytesRead = in.read(buffer)) > 0) {
                    out.write(buffer, 0, bytesRead);
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        } else {
            response.getWriter().println("File not found!");
        }
    }
}

package cn.juwatech.controller;
import org.springframework.core.io.FileSystemResource;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
@Controller
public class FileDownloadController {
    private static final String DOWNLOAD_FOLDER = "/path/to/download/directory/";
    @GetMapping("/download")
    public ResponseEntity<FileSystemResource> downloadFile(String fileName) throws IOException {
        Path path = Paths.get(DOWNLOAD_FOLDER + fileName);
        File file = path.toFile();
        if (file.exists()) {
            HttpHeaders headers = new HttpHeaders();
            headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
            headers.setContentLength(file.length());
            headers.setContentDispositionFormData("attachment", fileName);
            return new ResponseEntity<>(new FileSystemResource(file), headers, HttpStatus.OK);
        } else {
            return new ResponseEntity<>(HttpStatus.NOT_FOUND);
        }
    }
}