AWS SDK with Kotlin

2024-05-28

Boy was I happy when I read the news about the general availability of the AWS SDK for Kotlin. Finally—time to use Kotlin for my infrastructure-as-code projects.

https://aws.amazon.com/about-aws/whats-new/2023/11/aws-sdk-kotlin/

In this tutorial I follow Amazon’s guide on how to create an S3 bucket, put an object from a ByteStream into the S3 bucket, and then clean up everything using the AWS SDK for Kotlin. I had to make a few changes to the original tutorial to make it work in my development environment. All in all, it was straightforward.

Here is the general AWS SDK for Kotlin page: https://aws.amazon.com/sdk-for-kotlin/

The tutorial I followed is here: https://docs.aws.amazon.com/sdk-for-kotlin/latest/developer-guide/get-started.html

First, create a Gradle project. I kept the default settings.

% mkdir aws-cdk-kotlin
% cd aws-cdk-kotlin
% gradle init --type kotlin-application --dsl kotlin

Project name (default: aws-cdk-kotlin):

Source package (default: aws.cdk.kotlin):

Enter target version of Java (min. 7) (default: 21):

Generate build using new APIs and behavior (some features may change in the next minor release)? (default: no) [yes, no]

> Task:init
To learn more about Gradle by exploring our Samples at https://docs.gradle.org/8.5/samples/sample_building_kotlin_applications.html

BUILD SUCCESSFUL in 5s
2 actionable tasks: 2 executed
%

Next, add the AWS SDK dependency.

in build.gradle.kts

...

dependencies {
    ...
    implementation("aws.sdk.kotlin:s3:1.0.0")
}

Here is the tutorial code, slightly adapted to newer syntax:

import aws.sdk.kotlin.services.s3.S3Client
import aws.sdk.kotlin.services.s3.model.*
import aws.smithy.kotlin.runtime.content.ByteStream
import kotlinx.coroutines.runBlocking
import java.util.*

val REGION = "eu-central-1"
val BUCKET = "bucket-${UUID.randomUUID()}"
val KEY = "my-s3-bucket-key"

fun main(): Unit = runBlocking {
    S3Client.fromEnvironment { region = REGION }.use { s3 ->
        setupTutorial(s3)

        println("Creating object $BUCKET/$KEY...")

        val putObjectRequest = PutObjectRequest {
            bucket = BUCKET
            key = KEY
            body = ByteStream.fromString("Testing with the Kotlin SDK")
        }
        s3.putObject(putObjectRequest)

        println("Object $BUCKET/$KEY created successfully!")
        cleanUp(s3)
    }
}

suspend fun setupTutorial(s3: S3Client) {
    println("Creating bucket $BUCKET...")
    val createBucketRequest = CreateBucketRequest {
        bucket = BUCKET
        createBucketConfiguration {
            locationConstraint = BucketLocationConstraint.fromValue(REGION)
        }
    }
    s3.createBucket(createBucketRequest)
    println("Bucket $BUCKET created successfully!")
}

suspend fun cleanUp(s3: S3Client) {
    println("Deleting object $BUCKET/$KEY...")
    val deleteObjectRequest = DeleteObjectRequest {
        bucket = BUCKET
        key = KEY
    }
 s3.deleteObject(deleteObjectRequest)

 println("Object $BUCKET/$KEY deleted successfully!")

 println("Deleting bucket $BUCKET...")
 val deleteBucketRequest = DeleteBucketRequest {
  bucket = BUCKET
 }
 s3.deleteBucket(deleteBucketRequest)
 println("Bucket $BUCKET deleted successfully!")
}

Let my friend ChatGPT explain what the code does:

Imports: The code imports necessary classes from the AWS SDK for Kotlin, including S3 client classes and models. It also imports ByteStream for handling data streams and runBlocking for coroutine support.
Constants:
REGION: Specifies the AWS region (e.g., “eu-central-1”).
BUCKET: A unique bucket name is generated using UUID.randomUUID().
KEY: Defines the key name for the object to be stored in S3.
Main Function:
Initializes an S3 client with the specified region.
Calls setupTutorial to create a new S3 bucket.
Creates a text object in the bucket with the specified key.
Cleans up by deleting the created object and bucket.
setupTutorial Function:
Creates an S3 bucket in the specified region.
Uses CreateBucketRequest to configure and create the bucket.
cleanUp Function:
Deletes the previously created object and bucket.
Uses DeleteObjectRequest and DeleteBucketRequest for deletion.
Coroutine Usage: The runBlocking coroutine builder is used to execute suspend functions (setupTutorial and cleanUp) in main. AWS SDK calls are suspending functions and require a coroutine context.

Thank you, ChatGPT.

Finally, I ran the code and received the expected output:

Creating bucket bucket-bad30829-1f4f-432a-acf3-fccafac14ecf...
Bucket bucket-bad30829-1f4f-432a-acf3-fccafac14ecf created successfully!
Creating object bucket-bad30829-1f4f-432a-acf3-fccafac14ecf/my-s3-bucket-key...
Object bucket-bad30829-1f4f-432a-acf3-fccafac14ecf/my-s3-bucket-key created successfully!
Deleting object bucket-bad30829-1f4f-432a-acf3-fccafac14ecf/my-s3-bucket-key...
Object bucket-bad30829-1f4f-432a-acf3-fccafac14ecf/my-s3-bucket-key deleted successfully!
Deleting bucket bucket-bad30829-1f4f-432a-acf3-fccafac14ecf...
Bucket bucket-bad30829-1f4f-432a-acf3-fccafac14ecf deleted successfully!

That was easy!

If you have any further questions, need specific code examples, or require additional assistance, please leave a comment or send me a message.

Thank you for reading!