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

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

    private static final int BUFFER_SIZE = 1024;

    /**
     * 文件下載限速
     *
     * @param in             輸入流
     * @param out            輸出流
     * @param bytesPerSecond 每秒允許下載的字節(jié)數(shù)
     * @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) {
                // 將數(shù)據(jù)寫入輸出流
                out.write(buffer, 0, bytesRead);
                bytesSent += bytesRead;

                if (bytesSent >= bytesPerSecond) {
                    long elapsedTime = System.currentTimeMillis() - startTime;
                    if (elapsedTime < 1000) {
                        // 如果時(shí)間少于1秒，則休眠剩余時(shí)間
                        Thread.sleep(1000 - elapsedTime);
                    }
                    // 重置已發(fā)送字節(jié)計(jì)數(shù)和開始時(shí)間
                    bytesSent = 0;
                    startTime = System.currentTimeMillis();
                }
            }
        } catch (InterruptedException e) {
            // 恢復(fù)線程的中斷狀態(tài)
            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: 文件下載Controller
 * @author: shy
 * @date: 2024/06/28 10:48
 */
@RestController
@RequestMapping("/file")
public class FileController {

    // 每秒允許下載的字節(jié)數(shù)（例如100KB/s）
    private static final int BYTES_PER_SECOND = 1024 * 100; 

    @WithoutLogin
    @GetMapping("/download/{filename}")
    public ResponseEntity<StreamingResponseBody> downloadFile(@PathVariable String filename) {
        // 獲取要下載的文件
        File file = new File("D:\\tools\\" + filename);
        // 使用 StreamingResponseBody 實(shí)現(xiàn)流式響應(yīng)體
        StreamingResponseBody responseBody = outputStream -> {
            try (InputStream inputStream = Files.newInputStream(file.toPath())) {
                // 調(diào)用限速方法
                FileUtil.limitDownloadSpeed(inputStream, outputStream, BYTES_PER_SECOND);
            }
        };
        // 返回 ResponseEntity，包含響應(yīng)頭和流式響應(yīng)體
        return ResponseEntity.ok()
                .header(HttpHeaders.CONTENT_DISPOSITION, "attachment;filename=" + file.getName())
                .contentType(MediaType.APPLICATION_OCTET_STREAM)
                .contentLength(file.length())
                .body(responseBody);
    }
}