Difference between getEncoder and getUrlEncoder, getDecoder and getUrlDecoder in Java8 java.util.Base64 class

Difference between getEncoder and getUrlEncoder, getDecoder and getUrlDecoder in Java8 java.util.Base64 class

Starting with Java 8, encoding & decoding can be done using the java.util.Base64 class.

Base64.getEncoder().encode("hoge".getBytes());

This will do the encoding. There is another getUrlEncoder() method, which also performs encoding.

Base64.getUrlEncoder().encode("hoge".getBytes());

Difference between getEncoder and getUrlEncoder

The difference between getEncoder and getUrlEncoder is whether or not the Url is safe.

In the case of Url-safe, “+” is replaced by “-” and “/” by “_”; in the case of Url-unsafe, “+” and “/” are used as they are.

The difference between getDecoder and getUrlDecoder is the same.

Therefore, only if the encoded content does not contain “+” and “/”, it can be decoded correctly by getUrlDecoder when it is encoded by getEncoder.

The following is a sample code.

package purejava;

import java.util.Base64;

public class Base64Smaple {
  public static void main(final String[] args) {
    String in = "hogefuga";
    var encodeData = Base64.getEncoder().encode(in.getBytes()); // encode
    System.out.println(encodeData); // byte array

    var decodeData1 = new String(Base64.getDecoder().decode(encodeData));
    System.out.println(decodeData1); // hogefuga

    var decodeData2 = new String(Base64.getUrlDecoder().decode(encodeData));
    System.out.println(decodeData2); // hogefuga Can be decoded normally.
  }
}

However, if the result encoded by getEncoder contains “+” or “/”, decoding by getUrlDecoder will result in an error.

The same error may occur when encoding with getUrlEncoder and decoding with getDecoder. (Only when “-” and “_” are included.)

The following is a sample code that encodes with getEncoder and decodes with getUrlDecoder, resulting in an error.

package purejava;

import java.util.Base64;

public class Base64Smaple {

  public static void main(String[] args) {
    String in = "d!\"#$%&'()=~|";
    var encodeData = Base64.getEncoder().encode(in.getBytes()); // encode 
    System.out.println(new String(encodeData)); // ZCEiIyQlJicoKT1+fA== Contains "+".

    var decodeData1 = new String(Base64.getUrlDecoder().decode(encodeData)); // Error occurs because it cannot be decoded properly.
    // java.lang.IllegalArgumentException: Illegal base64 character 2b
    System.out.println(decodeData1);
  }
}

If you modify the decoding on line 12 of the above source to getDecoder, it will decode correctly.

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