Base64 Encoding in Fortress

Our example demonstrates base64 encoding and decoding in Java using the java.util.Base64 class.

import java.util.Base64;

public class Base64Example {
    public static void main(String[] args) {
        // Here's the string we'll encode/decode.
        String data = "abc123!?$*&()'-=@~";

        // Java provides standard and URL-safe base64 encoding.
        // Here's how to encode using the standard encoder.
        String sEnc = Base64.getEncoder().encodeToString(data.getBytes());
        System.out.println(sEnc);

        // Decoding may throw an IllegalArgumentException, which you can catch
        // if you're not sure the input is well-formed.
        try {
            byte[] sDec = Base64.getDecoder().decode(sEnc);
            System.out.println(new String(sDec));
        } catch (IllegalArgumentException e) {
            System.out.println("Decoding failed: " + e.getMessage());
        }
        System.out.println();

        // This encodes/decodes using a URL-safe base64 format.
        String uEnc = Base64.getUrlEncoder().encodeToString(data.getBytes());
        System.out.println(uEnc);
        try {
            byte[] uDec = Base64.getUrlDecoder().decode(uEnc);
            System.out.println(new String(uDec));
        } catch (IllegalArgumentException e) {
            System.out.println("Decoding failed: " + e.getMessage());
        }
    }
}

The string encodes to slightly different values with the standard and URL-safe base64 encoders (trailing = in standard encoding, and + vs - and / vs _), but they both decode to the original string as desired.

$ javac Base64Example.java
$ java Base64Example
YWJjMTIzIT8kKiYoKSctPUB+
abc123!?$*&()'-=@~

YWJjMTIzIT8kKiYoKSctPUB-
abc123!?$*&()'-=@~

In Java, we use the java.util.Base64 class for base64 encoding and decoding. This class provides separate encoders and decoders for standard and URL-safe base64 encoding.

The getEncoder() and getDecoder() methods return the standard Base64 encoder and decoder, while getUrlEncoder() and getUrlDecoder() return the URL-safe versions.

When encoding, we first convert our string to a byte array using getBytes(). The encodeToString() method then directly returns the encoded string.

For decoding, we use the decode() method which returns a byte array. We then convert this byte array back to a string.

Note that in Java, decoding an invalid base64 string throws an IllegalArgumentException, so it’s good practice to catch this exception when decoding user input or data from an untrusted source.

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