java - 如何使用 Spring Boot 在后端跟踪文件下载进度？

Question

我有一个 spring boot 应用程序，它有一个返回字符串和文本文件的 rest Controller 。 我想在服务器端跟踪下载进度，并将消息推送到队列。
当使用 HttpServlet 工作时，我只是从 HttpResponse 对象中获取了一个 OutputStream 并将字节推送到套接字上，计算进度，像这样:

    byte[] buffer = new byte[10];
    int bytesRead = -1;
    double totalBytes = 0d;
    double fileSize = file.length();

    while ((bytesRead = inStream.read(buffer)) != -1) {
        outStream.write(buffer, 0, bytesRead);
        totalBytes += bytesRead;
        queueClient.sendMessage(
                "job: " + job + "; percent complete: " + ((int) (totalBytes / fileSize) * 100));

        }

但是，对于 Spring Boot，由于很多事情都是在幕后发生的，所以我不是 100% 确定如何处理它。

我才刚刚开始使用 Spring Boot，请放轻松! 我的 Controller 目前看起来像这样:

@RestController
@RequestMapping("/api/v1/")
public class MyController {

    @Autowired
    QueueClient queue;

    @RequestMapping(value = "info/{id}", method = RequestMethod.GET)
    public String get(@PathVariable long id) {
        queue.sendMessage("Client requested id: " + id);
        return "You requested ID: " + id;
    }

    @RequestMapping(value = "files/{job}", method = RequestMethod.GET)
    public String getfiles(@PathVariable long job) {
        queue.sendMessage("Client requested files for job: " + job);
        return "You requested files for job " + job;
    }
}

我需要将文件从服务器流式传输到客户端，而不是先将整个文件加载到内存中。这对 spring REST Controller 是否可行？
我如何访问 HttpResponse 对象，或者有其他方法吗？

Answer 1

可以获取 HttpResponse 对象并可以下载大文件，如下所示:

@RequestMapping(value = "/files/{job}", method = RequestMethod.GET, produces=MediaType.APPLICATION_OCTET_STREAM_VALUE)
public void downloadFile(@PathVariable("job") String job, HttpServletResponse response) {

//Configure the input stream from the job
    InputStream file = new FileInputStream(fileStoragePath + "\\" + job);

    response.setHeader("Content-Disposition", "attachment; filename=\""+job+"\"");


    int readBytes = 0;
    byte[] toDownload = new byte[100];
    OutputStream downloadStream = response.getOutputStream();

    while((readBytes = file.read(toDownload))!= -1){
        downloadStream.write(toDownload, 0, readBytes);
    }
    downloadStream.flush();
    downloadStream.close(); 
}