Base64 Encoding: Illegal base64 character 3c

Question

I am trying to decode data in an xml format into bytes base64 and I am having an issues. My method is in java which takes a String data and converts it into bytes like as bellow.

String data = "......"; //string of data in xml format
byte[] dataBytes = Base64.getDecoder().decode(data);

Which failed and gave the exception like bellow.

java.lang.IllegalArgumentException: Illegal base64 character 3c
    at java.util.Base64$Decoder.decode0(Base64.java:714)
    at java.util.Base64$Decoder.decode(Base64.java:526)
    at java.util.Base64$Decoder.decode(Base64.java:549)
    at XmlReader.main(XmlReader.java:61)

Is the xml format not compatible with base64?

how can it be changed to a base64 string? Do I need to use encode? — VMA92, Sep 15 '17 at 13:18
Yes, of course. You have some human readable data like the one you have shown so far, then you `encode` it to base64 which will only have the allowed base64 chars, then you `decode` that base64 string into the original content again. — luk2302, Sep 15 '17 at 13:19
`DataString -> encode -> Base64String -> decode -> DataString` — luk2302, Sep 15 '17 at 13:20
so something like: byte[] dataBytes = Base64.getEncoder().encode(data.getBytes()); — VMA92, Sep 15 '17 at 13:21
Possible duplicate of: https://stackoverflow.com/questions/19743851/base64-java-encode-and-decode-a-string — luk2302, Sep 15 '17 at 13:22
Adding that you may also get this if you try to decode a "URL-safe" base64 string using the regular `Base64.getDecoder()` - in that case you have to use a utility that can handle such strings, e.g. `org.springframework.util.Base64Utils.decodeFromUrlSafeString()` — Janaka Bandara, Nov 04 '21 at 04:51

score 45 · Answer 1 · answered Nov 09 '18 at 18:22

45

Just use this method

getMimeDecoder()

String data = "......";
byte[] dataBytes =  Base64.getMimeDecoder().decode(data);

answered Nov 09 '18 at 18:22

Moddasir

1,449
13
33

2

In deed this works, though I'm curious what's the difference between those 2 APIs, docs are not quite helpful. – azizbekian Jun 04 '20 at 19:04
@azizbekian Mime decoder allows for illegal characters while trying to decode a Base64 string. – TheITDejan Mar 15 '21 at 14:13

score 6 · Answer 2 · answered Feb 01 '19 at 14:07

6

I got this same error and problem was that the string was starting with data:image/png;base64, ...

The solution was:

byte[] imgBytes = Base64.getMimeDecoder().decode(imgBase64.split(",")[1]);

answered Feb 01 '19 at 14:07

André Pacheco

1,780
14
19

And this is what I did `resp = resp.replace("data:image/jpeg;base64,", "");` – leventunver Jul 05 '19 at 13:24

score 2 · Answer 3 · answered Sep 15 '17 at 13:27

You should first get the bytes out of the string (in some character encoding).

For these bytes you use the encoder to create the Base64 representation for that bytes.

This Base64 string can then be decoded back to bytes and with the same encoding you convert these bytes to a string.

import java.nio.charset.StandardCharsets;
import java.util.Base64;

public class Base64Example {

  public static void main(String[] args) {
    final String xml = "<root-node><sub-node/></root-node>";
    final byte[] xmlBytes = xml.getBytes(StandardCharsets.UTF_8);
    final String xmlBase64 = Base64.getEncoder().encodeToString(xmlBytes);
    System.out.println(xml);
    System.out.println(xmlBase64);

    final byte[] xmlBytesDecoded = Base64.getDecoder().decode(xmlBase64);
    final String xmlDecoded = new String(xmlBytesDecoded, StandardCharsets.UTF_8);
    System.out.println(xmlDecoded);
  }

}

Output is:

<root-node><sub-node/></root-node>
PHJvb3Qtbm9kZT48c3ViLW5vZGUvPjwvcm9vdC1ub2RlPg==
<root-node><sub-node/></root-node>

score -7 · Accepted Answer · answered Sep 15 '17 at 13:27

-7

Thanks to @luk2302 I was able to resolve the issue. Before decoding the string, I need to first encode it to Base64

    byte[] dataBytes = Base64.getEncoder().encode(data.getBytes());
    dataBytes = Base64.getDecoder().decode(dataBytes);

answered Sep 15 '17 at 13:27

VMA92

469
2
8
19

18

Are you just encoding text and decoding it right away? If so, I fail to understand what's achieved through this. – leokhorn Aug 29 '18 at 08:25
Probably the encode function is correcting the encoding mismatch that is not making the conversion work at first instance – funder7 Aug 16 '20 at 17:06
1

@funder7 With this you end up with the *original (encoded)* string, not the real decoded value - encoded (by someone else) -> encoded (by you) -> decoded (by you) = encoded (by someone else); i.e. the original – Janaka Bandara Nov 04 '21 at 04:48

Base64 Encoding: Illegal base64 character 3c

4 Answers4

Linked