This article is the 7th day article of Hands Lab Advent Calendar 2019.

Good work. @naokiur. I will be in charge of this year as well.

Recently, when building AWS resources in business, With CloudFormation and Serverless I try to code it. (Keeping the dosage and remembering the purpose ...)

Thanks to that, I'm getting used to writing YAML format files.

Meanwhile, Knowing the existence of AWS CDK What's more, AWS CDK makes it generally available for Java and .NET! !!

I personally like Java, I tried AWS CDK in Java.

Overview I was also recommended, CDK Workshop published by AWS CDK It was really good for me who didn't do anything!

environment

MacBook Pro (Retina 13-inch、Early 2015)
macOS Mojave 10.14.6
Java 1.8.0_191
IntelliJ IDEA CE 2019.2.4

What i did

I recently created Step Functions in my work, so We built StepFunctions on AWS CDK.

cdk command installation

npm install -g aws-cdk

Create project template

You can generate a project template for Java with the following command.

cdk init --a {project name} --language java

Maven project. I personally miss it. Here, we set project name = sample.

App and Stack

When you generate a project template, SampleApp and SampleStack have been generated.

Stack is, as the name suggests This will be 1 Stack of CloudFormation, I am aware that.

By default It seems that it is a Stack that creates SQS and SNS.

pom.xml Apart from core Dependencies are listed for each AWS service. If you use more AWS services, it seems that you need to add dependencies.

Building Step Functions

Delete the default SQS and SNS, Add Lambda and Step Functions to Stack.

Add dependency

Add the Lambda and StepFunctions libraries to pom.xml.

`pom.xml`


<dependency>
    <groupId>software.amazon.awscdk</groupId>
    <artifactId>lambda</artifactId>
    <version>1.18.0</version>
</dependency>
<dependency>
    <groupId>software.amazon.awscdk</groupId>
    <artifactId>stepfunctions</artifactId>
    <version>1.18.0</version>
</dependency>
<dependency>
    <groupId>software.amazon.awscdk</groupId>
    <artifactId>stepfunctions-tasks</artifactId>
    <version>1.18.0</version>
</dependency>

Regarding StepFunctions Not just stepfunctions You need to add stepfunctions-tasks.

Add resources to Stack

Add Lambda and Step Functions resources. In the form of {Resource} .Builder.hoge (). Fuga () .build () It seems that it is often possible to generate resources.

It's my personal preference, but I feel that the description is complete and easy to read.

`SampleStack.java`


public class SampleStack extends Stack {
    public SampleStack(final Construct parent, final String id) {
        this(parent, id, null);
    }

    public SampleStack(final Construct parent, final String id, final StackProps props) {
        super(parent, id, props);

        final Function hello = Function.Builder.create(this, "HelloHandler")
                .runtime(Runtime.PYTHON_3_6)
                .code(Code.fromAsset("lambda"))
                .handler("hello.lambda_handler")
                .build();

        final Function world = Function.Builder.create(this, "WorldHandler")
                .runtime(Runtime.PYTHON_3_6)
                .code(Code.fromAsset("lambda"))
                .handler("world.lambda_handler")
                .build();

        final Task helloTask = Task.Builder.create(this, "HelloTask")
                .task(InvokeFunction.Builder.create(hello).build())
                .build();

        final Task worldTask = Task.Builder.create(this, "WorldTask")
                .task(InvokeFunction.Builder.create(world).build())
                .build();

        final StateMachine machine = StateMachine.Builder.create(this, "SampleStateMachine")
                .definition(helloTask.next(worldTask))
                .build();
    }
}

Lambda file storage

The method that actually works on Lambda is It seems that it needs to be stored under the directory in the same row as the src directory.

The method that actually runs on Lambda does not have to be Java, so I prepared a Python file here.

Deploy

Since it was not executed, first execute the following command.

cdk bootstrap

It will create a Stack to create an S3 bucket for deployment.

For deployment Execute the following command.

mvn package cdk deploy

By the above, You have created a Stack on CloudFormation.

resource

Step Functions was created successfully I was able to do it!

Impressions

Naturally, I felt that I had to decide what was needed to configure each AWS resource, and I needed to translate and write which Java class it applies to.
However, the name is easy to understand (* personal impression), so I wonder if it's a hassle.
I was a little lost because I didn't know where the Invoke Function` was.
If you read (TypeScript) sample properly, you shouldn't get lost ...
I got an error when deploying, fixing it, deploying, and then an error ... that's not at all
Maybe because it's a simple configuration ...
If you make a mistake, it will make a compile error.
** Complement is wonderful! !! !! ** **

Hands Lab Advent Calendar 2019, The 8th day is @watarukura!

I used it as a reference

https://cdkworkshop.com/

[JAVA] I built Step Functions with AWS CDK.