Base64 encoding in Java / Groovy

Question

What is the proper way to convert a byte [] to a Base64 string in Java? Better yet would be Grails / Groovy because it tells me that the encodeAsBase64() functi

Answer 1

Apache Commons has many utilities:

Binary Package: http://commons.apache.org/codec/apidocs/org/apache/commons/codec/binary/Base64.html

Download: http://commons.apache.org/codec/download_codec.cgi

Answer 2

Implement your own method like this :)

public class Coder {
private static final String base64code = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

public static String encodeAsBase64(String toEncode) {
    return encodeAsBase64(toEncode.getBytes())
}

public static String encodeAsBase64(byte[] toEncode) {
    int pos = 0;
    int onhand = 0;

    StringBuffer buffer = new StringBuffer();
    for(byte b in toEncode) {
        int read = b;
        int m;
        if(pos == 0) {
            m = (read >> 2) & 63;
            onhand = read & 3;
            pos = 1;
        } else if(pos == 1) {
            m = (onhand << 4) + ((read >> 4) & 15);
            onhand = read & 15;
            pos = 2;
        } else if(pos == 2) {
            m = ((read >> 6) & 3) + (onhand << 2);
            onhand = read & 63;
            buffer.append(base64code.charAt(m));
            m = onhand;
            onhand = 0;
            pos  = 0;
        }
        buffer.append(base64code.charAt(m));
    }
    while(pos > 0 && pos < 4) {
        pos++;
        if(onhand == -1) {
            buffer.append('=');
        } else {
            int m = pos == 2 ? onhand << 4 : (pos == 3 ? onhand << 2 : onhand);
            onhand = -1;
            buffer.append(base64code.charAt(m));
        }
    }
    return buffer.toString()
}

}

Answer 3

You could use the open source Base64Coder library

import biz.source_code.base64Coder.Base64Coder

@Grab(group='biz.source_code', module='base64coder', version='2010-09-21')

String s1 = Base64Coder.encodeString("Hello world")
String s2 = Base64Coder.decodeString("SGVsbG8gd29ybGQ=")

Answer 4

(adding this to this thread in the hopes that somebody else will get a hit on this and doesn't have to waste his valuable time)

I got stymied today when I tried to add in my Grails 2.3.11/Groovy 2.1.9 application the output of

String src = render(
        model:    ...,
        template: ...,
    )
    .encodeAsBase64()

as a data- attribute to a DOM element. But the atob() in the corresponding JavaScript, i.e. the code that decodes the Base64 string from the data attribute, kept complaining about illegal characters, while other decoders, e.g. base64 -d accepted the same Base64 string without problems.

The solution is to force the render() return value to a single string and then apply the Base64 encoding, i.e.

String src = render(
        model:    ...,
        template: ...,
    )
    .toString()
    .encodeAsBase64()

or (if you consider encodeAsBase64() as deprecated):

String src = render(
        model:    ...,
        template: ...,
    )
    .toString()
    .bytes
    .encodeBase64() // add 'true' for chunked output

Answer 5

The preferred way to do this in groovy is:

 def encoded = "Hello World".bytes.encodeBase64().toString()
 assert encoded == "SGVsbG8gV29ybGQ="
 def decoded = new String("SGVsbG8gV29ybGQ=".decodeBase64())
 assert decoded == "Hello World"