Decoding a Base64 string in Java

Question

I'm trying to decode a simple Base64 string, but am unable to do so. I'm currently using the org.apache.commons.codec.binary.Base64 package.

The test string I'm using is: abcdefg, encoded using PHP YWJjZGVmZw==.

This is the code I'm currently using:

Base64 decoder = new Base64();
byte[] decodedBytes = decoder.decode("YWJjZGVmZw==");
System.out.println(new String(decodedBytes) + "\n") ;

The above code does not throw an error, but instead doesn't output the decoded string as expected.

well, first of all, you should always specify a character set when converting from bytes to chars, perhaps "US-ASCII" for you example string (new String(decodedBytes, "US-ASCII")). — jtahlborn
– jtahlborn, Commented Jul 18, 2012 at 15:13
@jtahlborn the apache commons codec is built to "just work" in system default encoding if you don't specify otherwise — Affe
– Affe, Commented Jul 18, 2012 at 15:18
@TomasB code you posted works fine for me, is that the full sample? — Affe
– Affe, Commented Jul 18, 2012 at 15:18
@Affe - i have no idea what you mean by it "just working in the system default encoding". regardless of the library used, when you convert bytes to chars, you should always specify a charset. — jtahlborn
– jtahlborn, Commented Jul 18, 2012 at 15:22
If it prints nothing, the problem is elsewhere in your program, not with the Base-64 decoding. — erickson
– erickson, Commented Jul 18, 2012 at 15:27

RTB · Accepted Answer · 2012-07-18 16:01:57Z

80

Modify the package you're using:

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

And then use it like this:

byte[] decoded = Base64.decodeBase64("YWJjZGVmZw==");
System.out.println(new String(decoded, "UTF-8") + "\n");

edited Jul 18, 2012 at 16:01

answered Jul 18, 2012 at 15:16

RTB

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6 Comments

Diego Agulló Over a year ago

Be careful with sun.* packages! stackoverflow.com/questions/469695/decode-base64-data-in-java

TomasB Over a year ago

Sorry I should specified that I have to use org.apache.commons.codec.binary.Base64 because it's a safe url decoder.

vbezhenar Over a year ago

There's javax.xml.bind.DatatypeConverter.parseBase64Binary in JDK so you don't need to use sun API or external libraries to work with base64.

maasg Over a year ago

@RTB you should always use a characted encoding when constructing a string from a byte[]. Change to e.g. new String(decoded, "UTF-8")

RTB Over a year ago

@TomasB If my anwser helped please accept it so others can learn form it. If not how can i help you further?

|

Denys · Accepted Answer · 2019-05-01 20:44:08Z

20

If you don't want to use apache, you can use Java8:

byte[] decodedBytes = Base64.getDecoder().decode("YWJjZGVmZw=="); 
System.out.println(new String(decodedBytes) + "\n");

answered May 1, 2019 at 20:44

Denys

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Comments

Hany Sakr · Accepted Answer · 2017-07-23 07:17:05Z

18

The following should work with the latest version of Apache common codec

byte[] decodedBytes = Base64.getDecoder().decode("YWJjZGVmZw==");
System.out.println(new String(decodedBytes));

and for encoding

byte[] encodedBytes = Base64.getEncoder().encode(decodedBytes);
System.out.println(new String(encodedBytes));

answered Jul 23, 2017 at 7:17

Hany Sakr

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Comments

Alberto Perez · Accepted Answer · 2015-03-03 09:38:35Z

3

Commonly base64 it is used for images. if you like to decode an image (jpg in this example with org.apache.commons.codec.binary.Base64 package):

byte[] decoded = Base64.decodeBase64(imageJpgInBase64);
FileOutputStream fos = null;
fos = new FileOutputStream("C:\\output\\image.jpg");
fos.write(decoded);
fos.close();

answered Mar 3, 2015 at 9:38

Alberto Perez

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3 Comments

Darrell Teague Over a year ago

Base64 is a byte[] encoding specification and has nothing specifically to do with images nor is such a practice common.

VivaLaPanda Over a year ago

Base 64 encoding of images is common on older or less sophisticated messaging protocols.

James Daily Over a year ago

It's common enough to encode images in base64 when embedding them in XML documents or in HTML data URIs.

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