‘serverless invoke local’ with Java Lambdas

If you create a Java Lambda with the provided template, you’re probably returning a response using the provided ApiGatewayResponseClass. If you run your Lambda locally with ‘serverless invoke local –function functioname’, you’ll see a response like this:

Serverless: Invoke invoke:local
Serverless: In order to get human-readable output, please implement "toString()" method of your "ApiGatewayResponse" object.


Any other logger output will appear in your console, but in order to see the actual content of your ApiGatewayResponse, add a toString() method as the message suggests.

You include any of the properties in ApiGatewayResponse, but if you’re just interested in the JSON payload in the body of the response, then just adding this will return the body:

public String toString(){
    return this.body;

Learning Java 8 Streams

I’ve never had a good opportunity to use Java 8 Streams since traditional iteration approaches always seemed to be appropriate for what I needed. Working on my Sudoku related projects (in particular an implementation of a Human Solver) I needed an approach to count occurrences of numbers in Lists and also find where pairs existed in Lists.

To get started, I started with a number of simpler examples to gradually work up to what I was looking for. I’ve collected a number of my examples in this project here.

Creating a new AWS Lambda project with Serverless

Assuming the Serverless cli is already installed (here), init a new project with ‘serverless’ and answer the following questions:

% serverless       
 Serverless: No project detected. Do you want to create a new one? Yes
 Serverless: What do you want to make? AWS Node.js
 Serverless: What do you want to call this project? lambda-example
 Project successfully created in 'lambda-example' folder.

To deploy, run ‘serverless deploy’

AWS CloudFormation basics – part1

Collection of notes, templates and tips for building AWS CloudFormation templates.

The basic structure of CloudFormation files (in JSON):

  "Resources" : {
    "ExampleResourceName" : {
      "Type" : "AWS::?::?",
      "Properties" : {
        "Example" : "propertyvalue"
  • Resources: the AWS services to be provisioned. There can be multiple repeating Resource elements in this section, to provision/configure multiple services in a stack
  • ExampleResourceName: a name for each resource being provisioned
  • Type: the AWS type for the resource, e.g. AWS::S3::Bucket
  • Properties: properties for the service being provisioned/configured

AWS CLI commands:

aws cloudformation create-stack --stack-name STACK-NAME
  --template-body file://template-file.json
  --parameters ParameterKey=example1,ParameterValue=value1    
aws cloudformation list-stacks
aws cloudformation delete-stack --stack-name STACK-NAME

If your stack creates IAM resources, you’ll also need to pass:


Otherwise you’ll see this error:

An error occurred (InsufficientCapabilitiesException) when calling the CreateStack operation: Requires capabilities : [CAPABILITY_NAMED_IAM]