Issue with Encoding base64 in PHP and Decoding base64 in Java

Question

A string-"gACA" encoded in PHP using base64. Now I'm trying to decode in java using base64. But getting absurd value after decoding. I have tried like this:

public class DecodeString{
{
      public static void main(String args[]){
      String strEncode = "gACA";   //gACA is encoded string in PHP
      byte byteEncode[] = com.sun.org.apache.xerces.internal.impl.dv.util.Base64.decode(strEncode );
      System.out.println("Decoded String" + new String(k, "UTF-8"));
      }
 }

Output: ??

Please help me out

@JohannisK : It's coming from the external system so it could be anything except `??` in advance we don't know in advance in this case — Samraan, May 11 '15 at 10:14

icza · Accepted Answer · 2015-05-11T11:22:27.117

2

Java has built-in Base64 encoder-decoder, no need extra libraries to decode it:

byte[] data = javax.xml.bind.DatatypeConverter.parseBase64Binary("gACA");
for (byte b : data)
    System.out.printf("%02x ", b);

Output:

80 00 80

It's 3 bytes with hexadecimal codes: 80 00 80

edited May 11 '15 at 11:22

answered May 11 '15 at 10:22

icza

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Drumnbass · Answer 2 · 2015-05-14T06:27:42.293

1

Try this, it worked fine for me (However I was decoding files):

Base64.decodeBase64(IOUtils.toByteArray(strEncode));

So it would look like this:

public class DecodeString{
{
  public static void main(String args[]){
  String strEncode = "gACA";   //gACA is encoded string in PHP
  byte[] byteEncode = Base64.decodeBase64(IOUtils.toByteArray(strEncode));
  System.out.println("Decoded String" + new String(k, "UTF-8));
  }
}

Note that you will need extra libraries:

edited May 14 '15 at 06:27

answered May 11 '15 at 10:14

Drumnbass

867
1
14
35

@Samraan -128, 0, -128 – Drumnbass May 11 '15 at 10:55
Note this will only work if you are at least using Java 8. This will not work on previous versions of Java as the Base64 class was introduced in version 8. – DavidR Jan 05 '16 at 19:12

score 1 · Answer 3 · edited May 23 '17 at 11:59

public static void main(String args[])  {

        String strEncode = "gACA";   //gACA is encoded string in PHP
        byte byteEncode[] = Base64.decode(strEncode);

        String result = new String(byteEncode, "UTF-8");
        char[] resultChar = result.toCharArray();
        for(int i =0; i < resultChar.length; i++)
        {
            System.out.println((int)resultChar[i]);
        }
        System.out.println("Decoded String: " + result);
    }

I suspect it's an encoding problem. Issue about 65533 � in C# text file reading this post suggest the first and last character are \“. In the middle there is a char 0. Your result is probably "" or "0", but with wrong encoding.

score 0 · Answer 4 · answered May 11 '15 at 10:17

First things first, the code you use should not compile, it's missing a closing quote after "UTF-8.

And yeah, "gACA" is a valid base64 string as the format goes, but it doesn't decode to any meaningful UTF-8 text. I suppose you're using the wrong encoding, or messed up the string somehow...

score 0 · Answer 5 · answered Sep 20 '21 at 02:49

RFC 4648 defines two alphabets.

PHP uses Base 64 Encoding
Java uses Base 64 Encoding with URL and Filename Safe Alphabet.

They are very close but not the exact same. In PHP:

const REPLACE_PAIRS = [
  '-' => '+',
  '_' => '/'
];
public static function base64FromUrlSafeToPHP($base64_url_encoded) {
  return strtr($base64_url_encoded, self::REPLACE_PAIRS);
}

public static function base64FromPHPToUrlSafe($base64_encoded) {
  return strtr($base64_encoded, array_flip(self::REPLACE_PAIRS));
}

Issue with Encoding base64 in PHP and Decoding base64 in Java

5 Answers5