Kotlin DynamoDB Object Mapping Sample

main.kt

import com.amazonaws.auth.AWSStaticCredentialsProvider
import com.amazonaws.auth.BasicAWSCredentials
import com.amazonaws.client.builder.AwsClientBuilder
import com.amazonaws.services.dynamodbv2.AmazonDynamoDBClientBuilder
import com.amazonaws.services.dynamodbv2.datamodeling.*
import com.amazonaws.services.dynamodbv2.model.BillingMode
import com.amazonaws.services.dynamodbv2.model.ResourceInUseException
import java.math.BigDecimal
import java.util.*

@DynamoDBTable(tableName = "kotlin_test_table")
data class DItem(
    @DynamoDBHashKey(attributeName="id")
    var id: String = "",

    @DynamoDBAttribute(attributeName = "kotlin_test")
    var kotlinTest: String? = null,

    @DynamoDBAttribute(attributeName = "kotlin_test_obj")
    var kotlinTestObj: KotlinTestObj? = null
)

@DynamoDBDocument
data class KotlinTestObj(
    var testUUID: UUID = UUID.randomUUID(),
    var testShort: Short = 99.toShort(),
    var testByte: Byte = 127,
    var testByteArray: ByteArray = ByteArray(16),
    var testBool: Boolean = true,
    var testInt: Int = 199,
    var testStr: String = "199",
    var testBigDecimal: BigDecimal = BigDecimal.TEN,
    var testFloat: Double = 20.0,
    var testDate: java.util.Date = java.util.Date(),
    var testNumberList: List<Double> = listOf(1.0, 3.0, 5.0),
    var testStringList: List<String> = listOf("abc", "def", "xyz"),
    var testNumberSet: Set<Double> = setOf(5.0, 3.0, 1.0),
    var testStringSet: Set<String> = setOf("abc", "def", "xyz"),
    var testMap1: MutableMap<String, Int> = mutableMapOf("key" to 1),
    var testMap2: MutableMap<String, String> = mutableMapOf("key" to "value"),
    @DynamoDBTyped(DynamoDBMapperFieldModel.DynamoDBAttributeType.S) var testEnum: Direction = Direction.LEFT
) {
    enum class Direction {
        UP, DOWN, LEFT, RIGHT
    }
}

fun main() {
    val awsCreds = BasicAWSCredentials("access_key_id", "secret_key_id")

    val endpoint = AwsClientBuilder.EndpointConfiguration("http://localhost:8000", "local")

    val ddb = AmazonDynamoDBClientBuilder.standard()
        .withCredentials(AWSStaticCredentialsProvider(awsCreds))
        .withEndpointConfiguration(endpoint)
        .build()

    val mapper = DynamoDBMapper(ddb)

    // create table
    try {
        ddb.createTable(
            mapper.generateCreateTableRequest(DItem::class.java)
                .withBillingMode(BillingMode.PAY_PER_REQUEST)
        )
    } catch (e: ResourceInUseException) {
        println("table already created.")
    }

    mapper.save(
        DItem(
            id = "kotlin-test-abc",
            kotlinTest = "kotlin-test-string",
            kotlinTestObj = KotlinTestObj()
        )
    )

    val record = mapper.load(DItem::class.java, "kotlin-test-abc")
    println(record)
}

Kotlin DynamoDB Example

Gradle Project Setup

Create a kotlin/jvm project in Intellij, add the following gradle dependency

compile 'com.amazonaws:aws-java-sdk-dynamodb:1.11.548'

Create DynamoDB Local

create a docker-compose.yml with the following config

version: '3'
services:
  dynamodb-local:
    image: amazon/dynamodb-local
    hostname: dynamodb
    restart: always
    command: -jar DynamoDBLocal.jar -sharedDb -dbPath /home/dynamodblocal/data/
    volumes:
      - /data/dynamodb:/home/dynamodblocal/data
    ports:
      - "8000:8000"

Run docker-compose up

Points to Note

• Every entity need empty constructor
• All fields must be var
• Only Supported Map<String, *>
• Enum needed special handling as shown