在 Spring Boot 中将 AWS S3 文件作为流下载 [英] Downloading AWS S3 file as a stream in Spring boot

问题描述

我想公开一个 API，以将 S3 存储桶文件内容作为流下载给其使用者.API URL 类似于/downloadfile/** 这是 GET 请求.

I want to expose an API to download a S3 bucket file content as stream to its consumers. The API URL is like /downloadfile/** which is GET request.

1. 现在我的返回类型应该是什么 我尝试使用 accept header=应用程序/八位字节流不起作用.
2. 我不想将文件的内容写入任何文件并发送.它应该作为流返回，就是这样.

这是我写到现在的控制器伪代码，它一直给我 406 错误.

Here is the controller pseudo code I wrote till now which is giving me 406 error all the time.

 @GetMapping(value = "/downloadfile/**", produces = { MediaType.APPLICATION_OCTET_STREAM_VALUE })
    public ResponseEntity<Object> downloadFile(HttpServletRequest request) {
       //reads the content from S3 bucket and returns a S3ObjectInputStream
       S3ObjectInputStream object = null;
       object = publishAmazonS3.getObject("12345bucket", "/logs/file1.log").getObjectContent();
       return object
    }

这里有什么关于这样做的方法以及我做错了什么的建议吗?

Any suggestions here on the way of doing this and what I am doing wrong?

推荐答案

我能够使用 Spring 的 StreamingResponseBody 类以流的形式下载文件.

I was able to download the file as a stream by using StreamingResponseBody class from Spring.

这是我使用的代码:

    @GetMapping(value = "/downloadfile/**", produces = { MediaType.APPLICATION_OCTET_STREAM_VALUE })
    public ResponseEntity<S3ObjectInputStream> downloadFile(HttpServletRequest request) {
       //reads the content from S3 bucket and returns a S3ObjectInputStream
       S3Object object = publishAmazonS3.getObject("12345bucket", "/logs/file1.log");
       S3ObjectInputStream finalObject = object.getObjectContent();

        final StreamingResponseBody body = outputStream -> {
            int numberOfBytesToWrite = 0;
            byte[] data = new byte[1024];
            while ((numberOfBytesToWrite = finalObject.read(data, 0, data.length)) != -1) {
                System.out.println("Writing some bytes..");
                outputStream.write(data, 0, numberOfBytesToWrite);
            }
            finalObject.close();
        };
        return new ResponseEntity<>(body, HttpStatus.OK);
    }

测试流媒体是否正确完成的方法是下载一个大约 400mb 的文件.通过传入 vm 选项将 Xmx 减少到 256mb.现在，比较使用和不使用 StreamingResponseBody 的下载功能，当使用传统的 OutputStreams 写入内容时，您将得到 OutofMemoryError

The way to test the streaming is done correctly or not is to have a file of around 400mb to download. Reduce your Xmx to 256mb by passing the in the vm options. Now, compare the download functionality with and without using StreamingResponseBody, you will get OutofMemoryError when using the conventional OutputStreams for writing the content

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