英文:
How create an endpoint for downloading a PDF and sharing the generation progress with Server-sent events
问题
我有一个端点，允许用户下载PDF。由于PDF生成通常需要超过20秒，我想在我们处理过程中向前端发送关于PDF生成进度的信息。我以前从未使用过服务器发送事件（Server-sent events），但我在Spring 4.3中进行了简单的测试，效果很好。但现在我不知道如何将其用于PDF下载。
目前，我正在将PDF写入响应中（"application/pdf"），但在这种情况下，我将无法返回"SseEmitter"对象。
您对于将进度流发送到前端并仍然能够提供PDF有任何建议吗？我应该使用WebSockets来替代SSE吗？也许使用两个不同的端点？欢迎任何建议。 
英文:
I have an endpoint which allow the user to download a PDF. As the PDF generation usually takes more than 20 seconds, I would like to send to the frontend information about the PDF generation progress while we are processing it. I had never used Server-sent events, but I did a simple test in Spring 4.3) and it works fine. But now I don't know how to use it for the PDF download.
Currently I'm writing the PDF in the response ("application/pdf"), but in this case I won't be able to return the object SseEmitter.
Do you have any suggestion for sending a progress stream to frontend and still being able to provide the PDF? Should I use websockets instead of SSE? Maybe two different endpoints? Any suggestion is welcome.
答案1
得分: 0
我的解决方案是使用了两个不同的端点：
第一个端点：提供进度流并将 PDF 内容持久化到数据库中。
第二个端点：下载 PDF。
我认为如果我之前没有在数据库中持久化这个 PDF 内容，我可能不会对这个解决方案感到满意，但事实恰恰相反，所以这样做是可以的。
英文:
My solution was using two different endpoints:
First endpoint: provide the progress stream and persist the PDF content in database
Second endpoint: download the PDF
I don't think I would be happy with this solution if I was not already persisting this PDF content in database anyway, but it was exactly the case, so it was fine.
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