大文件下载防内存溢出简单实现

摘要：利用StreamingResponseBody来防止内存溢出，实现大文件下载。

一、配置异步请求超时时间

/**
 * @Description: 异步请求配置类
 * @Date: Created in 17:19 2025/1/5
 * @Author: Cenobitor
 * @Modified By:
 * @since 0.1.0
 */
@Configuration
@EnableWebMvc
public class WebConfig implements WebMvcConfigurer {

    @Override
    public void configureAsyncSupport(AsyncSupportConfigurer configurer) {
        configurer.setTaskExecutor(taskExecutor());
        // 超时时间设置为6000s
        configurer.setDefaultTimeout(TimeUnit.SECONDS.toMillis(6000));
    }

    private AsyncTaskExecutor taskExecutor() {
        ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
        executor.setCorePoolSize(10); // 核心线程数
        executor.setMaxPoolSize(20);  // 最大线程数
        executor.setQueueCapacity(500); // 队列容量
        executor.setThreadNamePrefix("Async-");
        executor.initialize();
        return executor;
    }
}

二、本地、远程文件下载请求接口

private static final int MAX_CONCURRENT_DOWNLOADS = 5; // 最大并发下载数
    private final Semaphore semaphore = new Semaphore(MAX_CONCURRENT_DOWNLOADS);

    @RequestMapping( "/downloadFile")
    public ResponseEntity<StreamingResponseBody> downloadFile() {
        long start = System.currentTimeMillis();
        try {
            Path filePath = Paths.get("E:\\macOS Catalina 10.15 正式版 19A583 macOShome.com.dmg");
            StreamingResponseBody responseBody = outputStream -> {
                try (InputStream inputStream = Files.newInputStream(filePath)) {
                    StreamUtils.copy(inputStream, outputStream);
                }
            };
            HttpHeaders header = new HttpHeaders();
            header.setContentDispositionFormData("attachment", "macOS.dmg");
            header.setContentType(MediaType.APPLICATION_OCTET_STREAM);
            return new ResponseEntity<>(responseBody,header, HttpStatus.OK);
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            long end = System.currentTimeMillis();
            System.out.println("downloadFile cost: " + (end - start) + "ms");
        }
    }

    @RequestMapping( "/downloadRemoteFile")
    public ResponseEntity<StreamingResponseBody> downloadRemoteFile() {
        long start = System.currentTimeMillis();
        try {
            StreamingResponseBody responseBody = outputStream -> {
                URL resourceUrl = new URL("https://cdn.mysql.com/Downloads/MySQL-9.1/mysql-9.1.0-winx64-debug-test.zip");
                try (InputStream inputStream = new UrlResource(resourceUrl).getInputStream()) {
                    StreamUtils.copy(inputStream, outputStream);
                }
            };
            HttpHeaders header = new HttpHeaders();
            header.setContentDispositionFormData("attachment", "mysql.zip");
            header.setContentType(MediaType.APPLICATION_OCTET_STREAM);
            return new ResponseEntity<>(responseBody,header, HttpStatus.OK);
        } catch (Exception e) {
            throw new RuntimeException(e);
        } finally {
            long end = System.currentTimeMillis();
            System.out.println("downloadFile cost: " + (end - start) + "ms");
        }
    }

    @RequestMapping( "/downloadRemoteFileLimit")
    public ResponseEntity<StreamingResponseBody> downloadRemoteFileLimit() {

        if (!semaphore.tryAcquire()) {
            // 如果无法获取信号量，则返回503服务不可用状态
            return new ResponseEntity<>(HttpStatus.SERVICE_UNAVAILABLE);
        }

        try {
            StreamingResponseBody responseBody = outputStream -> {
                URL resourceUrl = new URL("https://cdn.mysql.com/Downloads/MySQL-9.1/mysql-9.1.0-winx64-debug-test.zip");
                try (InputStream inputStream = new UrlResource(resourceUrl).getInputStream()) {
                    byte[] buffer = new byte[1024];
                    int bytesRead;
                    Instant lastWrite = Instant.now();
                    long bytesPerSecond = 1024 * 100; // 例如，限制为100KB/s

                    while ((bytesRead = inputStream.read(buffer)) != -1) {
                        outputStream.write(buffer, 0, bytesRead);

                        long now = Instant.now().toEpochMilli();
                        long elapsed = now - lastWrite.toEpochMilli();
                        long expectedDelay = (bytesRead * 1000L / bytesPerSecond) - elapsed;

                        if (expectedDelay > 0) {
                            TimeUnit.MILLISECONDS.sleep(expectedDelay);
                        }

                        lastWrite = Instant.now();
                    }
                } catch (Exception e) {
                    // 处理异常
                    throw new RuntimeException("下载失败", e);
                }finally {
                    semaphore.release(); // 释放信号量
                }
            };

            HttpHeaders header = new HttpHeaders();
            header.setContentDispositionFormData("attachment", "mysql.zip");
            header.setContentType(MediaType.APPLICATION_OCTET_STREAM);
            return new ResponseEntity<>(responseBody, header, HttpStatus.OK);
        } catch (Exception e) {
            // 处理其他可能的异常，并释放信号量（如果需要）
            semaphore.release();
            throw e;
        }
    }

三、前端页面代码

<template>
  <div class="hello">
    <h1>{{ msg }}</h1>
    <p>
      For a guide and recipes on how to configure / customize this project,<br>
      check out the
      <a href="https://cli.vuejs.org" target="_blank" rel="noopener">vue-cli documentation</a>.
    </p>
  </div>
  <div class="download-wrap">
    <el-button type="primary" icon="el-icon-download" size="sm>ll" @click="downloadFile">下载文件</el-button>
    <el-button type="primary" icon="el-icon-download" size="sm>ll" @click="downloadRemoteFile">下载远程文件</el-button>
    <el-button type="primary" icon="el-icon-download" size="sm>ll" @click="downloadRemoteFileLimit">下载远程文件限速</el-button>
  </div>
</template>

<script>
import axios from "axios";

export default {
  name: 'HelloWorld',
  props: {
    msg: String
  },

  methods:{
    downloadFile() {
      console.log('下载文件开始');
      const downloadUrl = 'http://localhost:8080/downloadFile'; // 文件下载的链接
      window.open(downloadUrl);
      console.log('下载文件完成');
    },
    downloadRemoteFile() {
      console.log('下载文件开始');
      const downloadUrl = 'http://localhost:8080/downloadRemoteFile'; // 文件下载的链接
      window.open(downloadUrl);
      console.log('下载文件完成');
    },
    downloadRemoteFileLimit() {
      console.log('下载文件开始');
      const downloadUrl = 'http://localhost:8080/downloadRemoteFileLimit'; // 文件下载的链接
      window.open(downloadUrl);
      console.log('下载文件完成');
    },
  },
  mounted() {
    axios.get('http://localhost:8080/hello').then(res => {
      console.log(res);
    });
  },
}
</script>

<!-- Add "scoped" attribute to limit CSS to this component only -->
<style scoped>
h3 {
  margin: 40px 0 0;
}
ul {
  list-style-type: none;
  padding: 0;
}
li {
  display: inline-block;
  margin: 0 10px;
}
a {
  color: #42b983;
}
</style>