Handle empty string input for parseBase64Binary instead of throwing IllegalArgumentException

[SanderHestvik]

Hi, after #282, parseBase64Binary throws IllegalArgumentException when called with an empty string

Reading through https://www.w3.org/TR/xmlschema-2 it seems like this is valid input
There is even a test vector BASE64("") = "" in https://www.rfc-editor.org/rfc/rfc4648#section-10
https://github.com/jakartaee/jaxb-api/pull/282/files#diff-2eef69682cb2debd3c0bb837aceb2da7d800a9145e133c709f9e9fb6ef0c3391L707-L710

Let me know if you would like me to create another PR adding some more test coverage

[antoniosanct]

@SanderHestvik @lukasj
That's correct! Maybe a better solution would be:

public static byte[] _parseBase64Binary(String text) {
  if (null == text || text.length() % 4 != 0) {
    throw new IllegalArgumentException("base64 text invalid.");
  }

Then you could modify your PR changing with this snippet and delete the next if condition.

In addition to, you could add new asserts including RFC references:

Assert.assertEquals("", new String(DatatypeConverter.parseBase64Binary("")));
Assert.assertEquals("f", new String(DatatypeConverter.parseBase64Binary("Zg==")));
Assert.assertEquals("fo", new String(DatatypeConverter.parseBase64Binary("Zm8=")));
Assert.assertEquals("foo", new String(DatatypeConverter.parseBase64Binary("Zm9v")));
Assert.assertEquals("foob", new String(DatatypeConverter.parseBase64Binary("Zm9vYg==")));
Assert.assertEquals("fooba", new String(DatatypeConverter.parseBase64Binary("Zm9vYmE=")));
Assert.assertEquals("foobar", new String(DatatypeConverter.parseBase64Binary("Zm9vYmFy")));

Regards,
Antonio.

[SanderHestvik]

@lukasj Could you merge this?