Kotlin Gradle Spring Cloud Function Serverless Template

This is a boilerplate template for serverless using Spring Cloud Function. It uses Kotlin, Gradle and AWS but could be easily adapted.

I also have a non-spring template aws-kotlin-jvm-gradle which is included with the serverless distribution.

Requirements

• Serverless 1.24 or higher
• Gradle 4 and JDK8

Usage

# Create template
serverless create --template-url https://github.com/jswift/aws-kotlin-jvm-spring \
    --path helloworld --name hello && cd helloworld

# Build and deploy the hello world function
gradle deploy

Functions

There are a few ways to define functions in Spring Cloud Function, the method used here is to create classes that implement Function and use the auto scan feature. Spring will scan the com.serverless.functions namespace (defined in application.properties) for functions.

Handlers

Each function need's a corresponding handler class, unless the function will be accessed only by a http event (in which case it can use the ApiGatewayHandler).

Requests

Functions consume and produce plain java objects. When using the ApiGatewayHandler, functions can access the full details of the request (e.g. the headers and path variables) by wrapping the request object in Spring's Message object.

fun apply(t: Message<HelloRequest>): HelloResponse {
    val httpRequest = req.headers["request"] as? APIGatewayProxyRequestEvent ?: return HelloResponse("Failed to get request event")
    
    // Read headers, etc
    
    return HelloResponse("Hello, ${t.name ?: "World"}")
}