SpringBoot实现文件下载的限速功能

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * @desc: 文件工具类
 * @author: shy
 * @date: 2024/06/28 11:27
 */
public class FileUtil {

    private static final int BUFFER_SIZE = 1024;

    /**
     * 文件下载限速
     *
     * @param in             输入流
     * @param out            输出流
     * @param bytesPerSecond 每秒允许下载的字节数
     * @throws IOException
     */
    public static void limitDownloadSpeed(InputStream in, OutputStream out, int bytesPerSecond) throws IOException {
        byte[] buffer = new byte[BUFFER_SIZE];
        int bytesRead;
        long bytesSent = 0;
        long startTime = System.currentTimeMillis();
        try {
            while ((bytesRead = in.read(buffer)) != -1) {
                // 将数据写入输出流
                out.write(buffer, 0, bytesRead);
                bytesSent += bytesRead;

                if (bytesSent >= bytesPerSecond) {
                    long elapsedTime = System.currentTimeMillis() - startTime;
                    if (elapsedTime < 1000) {
                        // 如果时间少于1秒，则休眠剩余时间
                        Thread.sleep(1000 - elapsedTime);
                    }
                    // 重置已发送字节计数和开始时间
                    bytesSent = 0;
                    startTime = System.currentTimeMillis();
                }
            }
        } catch (InterruptedException e) {
            // 恢复线程的中断状态
            Thread.currentThread().interrupt();
            throw new IOException("Thread was interrupted", e);
        }
    }
}

import java.io.File;
import java.io.InputStream;
import java.nio.file.Files;

import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.servlet.mvc.method.annotation.StreamingResponseBody;

import com.shy.admin.common.annotation.WithoutLogin;
import com.shy.common.utils.FileUtil;

/**
 * @desc: 文件下载Controller
 * @author: shy
 * @date: 2024/06/28 10:48
 */
@RestController
@RequestMapping("/file")
public class FileController {

    // 每秒允许下载的字节数（例如100KB/s）
    private static final int BYTES_PER_SECOND = 1024 * 100; 

    @WithoutLogin
    @GetMapping("/download/{filename}")
    public ResponseEntity<StreamingResponseBody> downloadFile(@PathVariable String filename) {
        // 获取要下载的文件
        File file = new File("D:\\tools\\" + filename);
        // 使用 StreamingResponseBody 实现流式响应体
        StreamingResponseBody responseBody = outputStream -> {
            try (InputStream inputStream = Files.newInputStream(file.toPath())) {
                // 调用限速方法
                FileUtil.limitDownloadSpeed(inputStream, outputStream, BYTES_PER_SECOND);
            }
        };
        // 返回 ResponseEntity，包含响应头和流式响应体
        return ResponseEntity.ok()
                .header(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=" + file.getName())
                .contentType(MediaType.APPLICATION_OCTET_STREAM)
                .contentLength(file.length())
                .body(responseBody);
    }
}