Base64 encoding and decoding in Kotlin

This post will discuss Base64 encoding and decoding in Kotlin.

1. Using `Base64` class

The idea is to use the encodeToString() function from Base64.Encoder for encoding the specified byte array into the base64 encoded string. To decode the base64 encoded string back to the byte array, use the decode() function from the Base64.Decoder class.

import java.util.Base64

fun main() {

val string = "Some text"

// encode a string using Base64 encoder

val encoder: Base64.Encoder = Base64.getEncoder()

val encoded: String = encoder.encodeToString(string.toByteArray())

println("Encoded Data: $encoded")

// decode the encoded data

val decoder: Base64.Decoder = Base64.getDecoder()

val decoded = String(decoder.decode(encoded))

println("Decoded Data: $decoded")

}

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Output:

Encoded Data: U29tZSB0ZXh0
Decoded Data: Some text

You can’t use a basic encoding to encode an URL. You should use the “URL and Filename safe” type Base64 encoding and decoding scheme. The following code example demonstrates this:

import java.util.Base64

fun main() {

val url = "https://techiedelight.com/"

val encoded = Base64.getUrlEncoder().encodeToString(url.toByteArray())

println("Encoded URL: $encoded")

val decoded = String(Base64.getUrlDecoder().decode(encoded))

println("Decoded URL: $decoded")

}

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Output:

Encoded URL: aHR0cHM6Ly93d3cudGVjaGllZGVsaWdodC5jb20v
Decoded URL: https://techiedelight.com/

To encode a large block of text using the MIME encoder, use getMimeEncoder() and getMimeDecoder() functions.

import java.util.*

fun main() {

val buffer = StringBuilder()

for (i in 0..4) {

buffer.append(UUID.randomUUID().toString())

}

val string = buffer.toString()

val mimeEncoded = Base64.getMimeEncoder().encodeToString(string.toByteArray())

val mimeDecoded = String(Base64.getMimeDecoder().decode(mimeEncoded))

println(mimeDecoded)

}

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Output (may vary):

e2317f97-47d0-4799-b383-2a89070d5c1ef57d1659-3153-47d6-88a1-be3d5cca8cf526afb83c-c0db-4ef6-bd41-edc7ca4a691db744a484-f6fd-4f80-a7e4-4d8d3d7d3153309b3b8c-d4b3-4027-821b-85450c735616

2. Using `DatatypeConverter` class

The DatatypeConverter class provides printBase64Binary() and parseBase64Binary() functions, which can be used to convert an array of bytes into a string and vice-versa.

import javax.xml.bind.DatatypeConverter

fun main() {

val string = "Some text"

// encode a string using `Base64` encoder

val encoded = DatatypeConverter.printBase64Binary(string.toByteArray())

println("Encoded String: $encoded")

// decode the encoded data

val decoded = String(DatatypeConverter.parseBase64Binary(encoded))

println("Decoded String: $decoded")

}

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Output:

Encoded String: U29tZSB0ZXh0
Decoded String: Some text

That’s all about base64 encoding and decoding in Kotlin.

Base64 encoding and decoding in Kotlin

1. Using Base64 class

2. Using DatatypeConverter class

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1. Using `Base64` class

2. Using `DatatypeConverter` class