java - 为什么我的二进制数据从网络服务器获取后会变大？

Question

我需要通过 Python/Django 实现的 Web 服务提供二进制文件。问题是，当我使用 vbindiff 将原始文件与传输的文件进行比较时，我看到传输的文件上有尾随字节，遗憾的是它变得毫无用处。

客户端使用 Java 访问保存的二进制文件:

HttpURLConnection userdataConnection = null;
    URL userdataUrl = null;
    try {
        userdataUrl = new URL("http://localhost:8000/app/vuforia/10");

        userdataConnection = (HttpURLConnection) userdataUrl.openConnection();
        userdataConnection.setRequestMethod("GET");
        userdataConnection.setRequestProperty("Content-Type", "application/octet-stream");
        userdataConnection.connect();

        InputStream userdataStream = new BufferedInputStream(userdataConnection.getInputStream());
        try (ByteArrayOutputStream fileStream = new ByteArrayOutputStream()) {
            byte[] buffer = new byte[4094];
            while (userdataStream.read(buffer) != -1) {
                fileStream.write(buffer);
            }
            byte[] fileBytes = fileStream.toByteArray();
            try (FileOutputStream fos = new FileOutputStream("./test.dat")) {
                fos.write(fileBytes);
            }
        }
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }

我认为 HttpURLConnection.getInputStream 只读取响应的正文，或者不读取？

此代码在后端提供数据

在views.py中:

if request.method == "GET":
    all_data = VuforiaDatabase.objects.all()
    data = all_data.get(id=version)
    return FileResponse(data.get_dat_bytes())

在 models.py 中:

def get_dat_bytes(self):
    return self.dat_upload.open()

如何以 1:1 的方式传输二进制数据？

Answer 1

您忽略了InputStream.read的返回值。

来自documentation :

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.

您的代码假设每次调用 userdataStream.read(buffer) 时都会填充缓冲区，而不是检查实际读入 buffer 的字节数。

您根本不需要从输入流中读取。只需使用 Files.copy :

Path file = Paths.get("./test.dat");

try (InputStream userdataStream = new BufferedInputStream(userdataConnection.getInputStream())) {
    Files.copy(userdataStream, file, StandardCopyOption.REPLACE_EXISTING);
}