Illegal base64 character "a" using java.util.Base64 from within Scala

Question

Suppose I have the following Base64 encoded String from a github API call to a file:
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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.

Let contentEncoded be the string containing the encoded file. I tried the following:

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", ""))

However, all of them resulted in an error message: java.lang.IllegalArgumentException: Illegal base64 character a.

My question is: Am I not seeing something obvious? Are there some hidden control characters? Has anybody had similar issues and was able to fix them?

Answer 1

Just remove line breaks and it should work.

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

Answer 2

The following snippet decodes the encoding correctly:

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

as pointed out by comments, the error message Illegal Base64 character a corresponds to the hex value for the newline character \n. Using the Mime Decoder it is possible to decode the string without removing the newline characters beforehand.