java - Spring RestTemplate 将响应流式传输到另一个请求中

Question

我正在尝试使用 spring 的 RestTemplate 将文件下载的结果直接流式传输到另一篇文章中

我目前的做法如下:

   ResponseEntity<InputStreamResource> downloadResponse = restTemplate.getForEntity(fileToDownloadUri, InputStreamResource.class);

   InputStreamResource imageInputStreamResource = downloadResponse.getBody();

   ResponseEntity<String> response = restTemplate.exchange(storageUri, POST, new HttpEntity<>(imageInputStreamResource), String.class);

但是，我在运行上面的代码时遇到以下异常:

org.springframework.web.client.ResourceAccessException: I/O error on POST request for "http://host:port/path/some.jpg": stream is closed; nested exception is java.io.IOException: stream is closed

    at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:6
...
Caused by: java.io.IOException: stream is closed
    at sun.net.www.protocol.http.HttpURLConnection$HttpInputStream.ensureOpen(HttpURLConnection.java:3348)
    at sun.net.www.protocol.http.HttpURLConnection$HttpInputStream.read(HttpURLConnection.java:3373)

似乎响应总是作为处理的最后一步关闭。通过响应，HttpURLConnection 关闭，并且流不再可处理。

我希望能够实现这种情况，而不必将文件完全保存在内存中或将其写入文件(如 here 所述)。

非常感谢任何提示。

Answer 1

如果你想直接转发响应而不是将它保存在内存中，你必须直接写入响应:

@RequestMapping(value = "/yourEndPoint")
public void processRequest(HttpServletResponse response) {
    RestTemplate restTemplate = new RestTemplate();

    response.setStatus(HttpStatus.OK.value());

    restTemplate.execute(
        fileToDownloadUri,
        HttpMethod.GET,
        (ClientHttpRequest requestCallback) -> {},
        responseExtractor -> {
            IOUtils.copy(responseExtractor.getBody(), response.getOutputStream());
            return null;
        });
}