【Java】Upload file to web services

最新推荐文章于 2023-10-20 15:43:55 发布

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最新推荐文章于 2023-10-20 15:43:55 发布

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本文链接：https://blog.youkuaiyun.com/zhangjun2915/article/details/35286599

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本文讨论了一个WebserviceAPI的问题，即如何在API中上传二进制文件，如jar包，而不使用UTF-8编码。通过采用Base64编码，可以解决因编码效率和JSON限制导致的问题。文章提供了Java6内置的Base64编解码支持的示例。

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content = new String(DatatypeConverter.parseBase64Binary(content))

最近需要写一个web service API提供给前台调用，用以上传文件内容，API如下：

public void upload(String requestor, Script script, String content, boolean overwrite)

API所有的参数按json编码。最开始的需求是上传文本文件，比如脚本文件，所以content参数encoding定为UTF-8。但后来需要上传jar包这种二进制文件，用UTF-8就不行了，有一些编码会被json识别成非法字符，参考stackoverflow上的回答：

The problem with UTF-8 is that it is not the most space efficient encoding. Also, some random binary byte sequences are invalid UTF-8 encoding. So you can't just interpret a random binary byte sequence as some UTF-8 data because it will be invalid UTF-8 encoding. The benefit of this constrain on the UTF-8 encoding is that it makes it robust and possible to locate multi byte chars start and end whatever byte we start looking at.
As a consequence, if encoding a byte value in the range [0..127] would need only one byte in UTF-8 encoding, encoding a byte value in the range [128..255] would require 2 bytes ! Worse than that. In JSON, control chars, " and \ are not allowed to appear in a string. So the binary data would require some transformation to be properly encoded.

解决办法是采用Base64编码替换UTF-8。Java 6内置Base64编解码的支持：

content = new String(DatatypeConverter.parseBase64Binary(content));

DatatypeConverter.printBase64Binary(scriptfao.read(script).getBytes());