AWS CDK & JBang

01 March 2021

I am a big of AWS and the services it offers. What I am not a big fan of, is CloudFormation; in the sense that I don’t like to write huge YAML files to define my AWS resources. An alternative approach is to use a tool like Ansible, where learning it, at least can be used also for other Cloud providers like Azure. But still, as a Java Developer, I don’t feel comforable writing extensive/large YAML or JSON files.

Meet the AWS Cloud Development Kit (CDK), which essentially allows you to define your AWS resources by writing Java code.

CDK comes with a Node-based commandline, so you will first have to install Node 10+; now, install the aws-cdk CLI tool:

sudo npm install -g aws-cdk

Maven

What you could be doing now, is scaffold a Maven project and use it to define your recourses in Java code. Within an empty directory for your project run:

cdk init app --language=java

You can now import this into your IDE of choice, define resource in Java and then deploy it using cdk deploy assuming you have a default profile for AWS set up on your system/user (check ~/.aws/credentials).

This is already quiet nice and I can recommand you to have a look at the Video series by rickpil and the great CDK API reference.

JBang

What is even cooler, is that we can use it with JBang as well. If you take a look at the Maven project, it is just a regular project without any specific plugins. The only thing that makes it work and ties it to the cdk CLI tool, is the cdk.json in the root folder. It contains an app parameter which gives it a command to run the application (mvn -e -q compile exec:java). Actually, what is happening, is that the Java application will produce a CloudFormation template, which is than feed to AWS.

So, what we need for a minimalist AWS deployment script using JBang, is the below two files only.

awsdeployment.java
///usr/bin/env jbang "$0" "$@" ; exit $?
//DEPS software.amazon.awscdk:core:1.91.0
//DEPS software.amazon.awscdk:s3:1.91.0

import software.amazon.awscdk.core.App;
import software.amazon.awscdk.core.Construct;
import software.amazon.awscdk.core.Stack;
import software.amazon.awscdk.core.StackProps;
import software.amazon.awscdk.services.s3.Bucket;

import static java.lang.System.*;
import java.util.Arrays;

public class awsdeployment extends Stack {
    public static void main(final String[] args) {
        App app = new App();

        new awsdeployment(app, "AwsCdkTestStack");

        app.synth();
    }

    public awsdeployment(final Construct scope, final String id) {
        this(scope, id, null);
    }

    public awsdeployment(final Construct scope, final String id, final StackProps props) {
        super(scope, id, props);

        // Create an S3 bucket
        new Bucket(this, "MyBucket");

        // Create other resources...
    }
}
cdk.json
{
  "app": "jbang awsdeployment.java",
  "context": {
    "@aws-cdk/core:enableStackNameDuplicates": "true",
    "aws-cdk:enableDiffNoFail": "true",
    "@aws-cdk/core:stackRelativeExports": "true",
    "@aws-cdk/aws-ecr-assets:dockerIgnoreSupport": true,
    "@aws-cdk/aws-secretsmanager:parseOwnedSecretName": true,
    "@aws-cdk/aws-kms:defaultKeyPolicies": true,
    "@aws-cdk/aws-s3:grantWriteWithoutAcl": true
  }
}

When you run cdk deploy, it should deploy an S3 bucket named "MyBucket" to AWS.