使用Scala中的java.util.Base64时出现非法的base64字符“a”。

Question

假设我从Github API调用文件得到了以下Base64编码的字符串：

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dXQKfQ==

As far as I see, this encoding is correct and only contains the standard alphabet of characters for a Base64 encoding. If I decode this encoding here, I get a correct translation. However, I tried various approaches to decode it programmatically and did not find a solution yet.

假设contentEncoded是包含编码文件的字符串。我尝试了以下方法：

java.util.Base64.getDecoder.decode(contentEncoded)
java.util.Base64.getDecoder.decode(contentEncoded.getBytes)
java.util.Base64.getDecoder.decode(contentEncoded.getBytes(StandardCharsets.UTF_8))
java.util.Base64.getUrlDecoder.decode(contentEncoded))
java.util.Base64.getUrlDecoder.decode(contentEncoded.getBytes(StandardCharsets.UTF_8))
java.util.Base64.getMimeDecoder.decode(contentEncoded.replaceAll("\\n", "").replaceAll("\\r", ""))

然而，所有尝试都导致错误信息：java.lang.IllegalArgumentException: Illegal base64 character a。

我的问题是：我是否没有看到一些显而易见的东西？是否存在一些隐藏的控制字符？是否有人遇到过类似问题并且成功解决了？

- Tilman Zuckmantel

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你能否提供一个最小化、可重现的示例，例如通过提供你尝试过的代码和输入作为硬编码的String变量？编码数据似乎没问题，你声称调用的方法大部分应该是有效的。我猜测你的输入不是你所认为的那样。 - Joachim Sauer

看起来这个错误信息中的a是有问题字符的十六进制值，也就是U+000a，通常称为\n。换句话说：最后一行应该能够正常工作，但前面的行可能会失败。实际上，你需要要么在源代码中删除\n，要么只使用getMimeDecoder()：那个方法同样有效。 - Joachim Sauer

Answer 1

只需删除换行符即可正常工作。

contentEncoded.replace("\n", "")

- tentacle

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如果文本文件保存在Windows系统中，换行符是\r\n，建议使用replaceAll("\\R", "")。 - Andreas

为了使其多平台 - 使用 replaceALL("\r\n|\r|\n", "")。 - kosolapyj

迄今为止最佳答案。 - M.Ed

Answer 2

以下代码片段正确地解码了编码：

val decodedWithMime = java.util.Base64.getMimeDecoder.decode(contentEncoded)
val convertedByteArray = decodedWithMime.map(_.toChar).mkString

正如评论中指出的那样，错误信息Illegal Base64 character a对应于十六进制值为换行符\n。使用Mime解码器可以在不事先删除换行符的情况下解码字符串。

- Tilman Zuckmantel

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Java实现中的内容如下：byte[] decodedWithMime = .... 和 String convertedByteArray = new String(decodedWithMime)，不是上述所描述的Kotlin。 - DFeng