在浏览器下载中保留UTF-8 BOM [英] Preserve UTF-8 BOM in Browser Downloads
问题描述
我有一个JAX-RS REST服务，该服务生成一个CSV文件并将其流回浏览器.一切都设置为UTF-8，因此我通过浏览器下载的文件也是有效的UTF-8文件(无BOM)，该文件向我显示了有效，可读的UTF-8变音符号等，在Notepad ++，Sublime等中.
I have a JAX-RS REST-Service that produces a CSV file and streams it back to the browser. Everything is set to UTF-8, so also the file I download via the browser is a valid UTF-8 File (without a BOM) that shows me valid, readable UTF-8 umlauts, etc. in Notepad++, Sublime, etc..
在Excel中打开这样的文件虽然会导致无法读取的变音符号等，因为Excel显然试图使用另一个字符集(CP-1252，我想是打开它，但这并不重要).
Opening such a file in Excel though leads to unreadable umlauts, etc. since Excel apparently tries to open it with another charset (CP-1252, I guess, but that doesn't really matter).
通过Notepad ++使用BOM表保存文件并在Excel中重新打开该文件效果很好.好像检测BOM是Excel用于检测UTF-8的唯一方法.无论如何-我认为添加BOM可以有所帮助...
Saving the file with a BOM via Notepad++ and re-opening it in Excel works nicely. Seems like the detection of a BOM is the only way that Excel uses to detect UTF-8. Anyways - I thought that adding a BOM could help...
是的.结果相同.过了一会儿，我发现在某些情况下BOM会被删除:如果在BOM之前添加了任何字符，我会在Hex-Editor中看到BOM.删除该字符后，物料清单将不再存在.
Did that. Same result. After a while, I figured out that the BOM gets removed under some circumstances: If I added any character right before the BOM, I could see the BOM in my Hex-Editor. After removal of that character, the BOM wouldn't be there anymore.
当我继续并通过cURL下载文件时，我真的很惊讶. BOM在那里！直到我认为这可能与我的应用程序，内容类型，Encodigs，HTTP标头等有关–但它们似乎都没问题.
When I went on and downloaded the file via cURL I was really surprised. The BOM was there! Up until that I thought it might have to do with my application, Content-Types, Encodigs, HTTP Headers, etc. - but all of them seem to be fine.
现在，经过数小时的尝试，我对如何告诉浏览器保留BOM有了任何想法?我可以设置任何HTTP标头吗?由于Chrome，Internet Explorer，Edge，Firefox都删除了BOM，所以这听起来有点像浏览器的约定...
Now, after hours of trying out different things, any ideas on how I can tell the browser to keep the BOM? Is there any HTTP Header I could set? Since Chrome, Internet Explorer, Edge, Firefox all remove the BOM, this sounds a little bit like a browser convention to me...
非常感谢您的高度赞赏！
Many thanks for your highly appreciated help!
多亏了sideshowbarker的回答，我找到了一种解决方法，即在内容前添加两个BOM，因此在浏览器删除第一个BOM后将剩下一个BOM.
Thanks to sideshowbarker answer, I found a workaround by prepending two BOMs to the content, so there will be a BOM remaining after the first BOM gets removed by the browser.
推荐答案
我认为这可能是因为相关规范要求剥离BOM，而这正是浏览器所要做的.也就是说，浏览器符合编码规范中的UTF-8解码算法的要求. ，这是
I think this might be because the relevant specs require the BOM to be stripped out, and that’s what browsers do. That is, browsers conform to the requirements of the UTF-8 decode algorithm in the Encoding spec, which is this:
要以UTF-8解码字节流 stream ，请运行以下步骤:
To UTF-8 decode a byte stream stream, run these steps:
-
让缓冲区为空字节序列.
从 stream 读取三个字节到 buffer .
如果 buffer 与0xEF 0xBB 0xBF不匹配，则将 buffer 附加到 stream .
If buffer does not match 0xEF 0xBB 0xBF, prepend buffer to stream.
让输出为代码点流.
使用 stream 和 output 运行UTF-8的解码器.
Run UTF-8’s decoder with stream and output.
返回输出.
步骤3是导致BOM剥离的原因.
Step 3 is what causes the BOM to be stripped.
鉴于编码规范要求，我认为无法告诉浏览器保留BOM.
Given the Encoding spec requires that, I think there’s no way to tell browsers to keep the BOM.
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