How to convert a Data Class to ByteBuffer in Kotlin? - kotlin

Question

I am trying to use Kinesis, which expects data in byte buffer format. All the examples I have seen so far are in Java and pass simple strings.
Can anybody give an idea of how to convert a kotlin data class to bytebuffer?
e.g.
data class abc (
var a: Long,
var b: String,
var c: Double
)

Answer 1

Check the below method
fun toByteArray(): ByteArray? {
val size: Int = 8 + 8 + string.Size
val byteBuffer = ByteBuffer.allocate(size)
.put(long) //long veriable
.put(double) // double veriable
.put(string)
return byteBuffer.array()
}
You can allocate the size based on dataType size like Int 4 bytes, Double and Long 8 bytes
for reading back to dataType
val byteBuffer = ByteBuffer.wrap(byteArray)
byteBuffer.get(Int) //Int variable
byteBuffer.get(Double) //Double variable
byteBuffer.get(nonce)

Answer 2

You might want to have a look at kotlinx.serialization. It is an official Kotlin project and supports several formats out-of-the-box. You can use the output and wrap it in with ByteBuffer.wrap

Answer 3

Thanks for all the suggestions.
Solved the problem using ObjectMapper() of Jackson library (jackson-databind) and annotations.
Following code used for serialization:
val objectMapper = ObjectMapper()
objectMapper.registerModule(JavaTimeModule())
val buf = ByteBuffer.wrap(objectMapper.writeValueAsString(className).toByteArray(Charsets.UTF_8))
code for deserialization:
val objectMapper = ObjectMapper()
objectMapper.registerModule(JavaTimeModule())
val obj = objectMapper.readValue(Charsets.UTF_8.decode(record.data()).toString(), ClassName::class.java)
Apart from this, I had to add constructors of all the data classes and had to add the following annotation to all the LocalDateTime attributes:
#DateTimeFormat(iso = DateTimeFormat.ISO.DATE_TIME)
#JsonFormat(pattern = "YYYY-MM-dd HH:mm")
var edd: LocalDateTime?,

Answer 4

A simple solution with no additional libraries
Note: must be tailored for each data class
data class TimerConfig(val startTime: Long, val repeatCount: Int, val sequenceDuration: Int)
Converting the data class to a ByteArray
private fun TimerConfig.toByteArray(): ByteArray {
val byteBuffer = ByteBuffer.allocate(Long.SIZE_BYTES + Int.SIZE_BYTES + Int.SIZE_BYTES)
byteBuffer.putLong(this.startTime)
byteBuffer.putInt(this.repeatCount)
byteBuffer.putInt(this.sequenceDuration)
return byteBuffer.array()
}
Recovering the data class from the received ByteArray
private fun ByteArray.toTimerConfig(): TimerConfig {
val byteBuffer = ByteBuffer.wrap(this)
return TimerConfig(byteBuffer.long, byteBuffer.int, byteBuffer.int)
}