Base64 Java encode and decode a string

I want to encode a string into base64 and transfer it through a socket and decode it back.

But after decoding it gives different answer.

Following is my code and result is "77+9x6s="

import javax.xml.bind.DatatypeConverter;

    public class f{
    
       public static void main(String a[]){
       
          String str = new String(DatatypeConverter.parseBase64Binary("user:123"));
          String res = DatatypeConverter.printBase64Binary(str.getBytes());
          System.out.println(res);
       }
    }

Any idea about how to implement this?

You can use following approach:

import org.apache.commons.codec.binary.Base64;

// Encode data on your side using BASE64
byte[] bytesEncoded = Base64.encodeBase64(str.getBytes());
System.out.println("encoded value is " + new String(bytesEncoded));

// Decode data on other side, by processing encoded data
byte[] valueDecoded = Base64.decodeBase64(bytesEncoded);
System.out.println("Decoded value is " + new String(valueDecoded));

Hope this answers your doubt.

Java 8 now supports BASE64 Encoding and Decoding. You can use the following classes: java.util.Base64, java.util.Base64.Encoder and java.util.Base64.Decoder.

Example usage:

// encode with padding
String encoded = Base64.getEncoder().encodeToString(someByteArray);

// encode without padding
String encoded = Base64.getEncoder().withoutPadding().encodeToString(someByteArray);

// decode a String
byte [] barr = Base64.getDecoder().decode(encoded); 

The accepted answer uses the Apache Commons package but this is how I did it using Java's native libraries

Java 11 and up

import java.util.Base64;

public class Base64Encoding {

    public static void main(String[] args) {
        Base64.Encoder enc = Base64.getEncoder();
        Base64.Decoder dec = Base64.getDecoder();
        String str = "77+9x6s=";

        // encode data using BASE64
        String encoded = enc.encodeToString(str.getBytes());
        System.out.println("encoded value is \t" + encoded);

        // Decode data
        String decoded = new String(dec.decode(encoded));
        System.out.println("decoded value is \t" + decoded);
        System.out.println("original value is \t" + str);
    }
}

Java 6 - 10

import java.io.UnsupportedEncodingException;    
import javax.xml.bind.DatatypeConverter;

public class EncodeString64 {
	public static void main(String[] args) throws UnsupportedEncodingException {

		String str = "77+9x6s=";
		// encode data using BASE64
		String encoded = DatatypeConverter.printBase64Binary(str.getBytes());
		System.out.println("encoded value is \t" + encoded);

		// Decode data 
		String decoded = new String(DatatypeConverter.parseBase64Binary(encoded));
		System.out.println("decoded value is \t" + decoded);
		
		System.out.println("original value is \t" + str);
	}
}

The better way would be to try/catch the encoding/decoding steps but hopefully you get the idea.

For Spring Users , Spring Security has a Base64 class in the org.springframework.security.crypto.codec package that can also be used for encoding and decoding of Base64. Ex.

 public static String base64Encode(String token) {
	byte[] encodedBytes = Base64.encode(token.getBytes());
	return new String(encodedBytes, Charset.forName("UTF-8"));
}


public static String base64Decode(String token) {
	byte[] decodedBytes = Base64.decode(token.getBytes());
	return new String(decodedBytes, Charset.forName("UTF-8"));
}

The following is a good solution -

import android.util.Base64;

String converted = Base64.encodeToString(toConvert.toString().getBytes(), Base64.DEFAULT);

String stringFromBase = new String(Base64.decode(converted, Base64.DEFAULT));

That's it. A single line encoding and decoding.

import javax.xml.bind.DatatypeConverter;

public class f{

   public static void main(String a[]){

      String str = new String(DatatypeConverter.printBase64Binary(new String("user:123").getBytes()));
      String res = DatatypeConverter.parseBase64Binary(str);
      System.out.println(res);
   }
}