AWS Serverless Guide

Learn how to use AWS Serverless services in your Microlam app.

This guide covers:

  • Bootstrapping an application

  • Testing the application

  • Packaging of the application

  • Deploying to AWS

1. Prerequisites

To complete this guide, you need:

  • from 15 minutes to 1 hour

  • an IDE

  • JDK 21+ installed with JAVA_HOME configured appropriately

  • Apache Maven 3.8.1+

  • Docker



Verify Maven is using the Java you expect

If you have multiple JDK’s installed it is not certain Maven will pick up the expected java and you could end up with unexpected results. You can verify which JDK Maven uses by running mvn --version.

2. Using AWS profiles

2.1. Configuring your AWS Profiles

Using AWS profiles allow you to switch very easily between your differents AWS Accounts.

For example, imagine you are use 2 different accounts inside your company to access dev and prod environment, you will create 2 profiles:

  • companydev : for the dev environment

  • companyprod : for the prod environment

You can access AWS official documentation for reference or simply follow this guide:

All these profiles must be defined in the file ~/.aws/credentials like this:

aws_access_key_id = YOUR_ACCESS_KEY_ID
aws_secret_access_key = YOUR_SECRET_ACCESS_KEY

aws_access_key_id = YOUR_ACCESS_KEY_ID_DEV
aws_secret_access_key = YOUR_SECRET_ACCESS_KEY_DEV

aws_access_key_id = YOUR_ACCESS_KEY_ID_PROD
aws_secret_access_key = YOUR_SECRET_ACCESS_KEY_PROD

While you put the default region for each profile in the file ~/.aws/config like this:


[profile companydev]

[profile companyprod]

Then I suggest to test these profiles from your CLI, listing s3 files for each profile:

  • For the default profile:

aws s3 ls
  • For the profile companydev:

aws s3 ls --profile companydev
  • For the profile companyprod:

aws s3 ls --profile companyprod

If the output from these commands is the one you expect from each account, it means you successfully configured your profiles.

2.2. From the Java code (devops)

When you create a new Microlam Project from the maven archetype microlam-lambda-quickstart you will find a class Aws in src/test/java:



public enum Aws {

	PROD("companyprod", "eu-west-1", "companyprod-deployment", true);

	public final String profile;
	public final String region;
	public final String bucket;
	public final boolean useS3TransferAcceleration;

	private Aws(String profile, String region, String bucket, boolean useS3TransferAcceleration) {
		this.profile = profile;
		this.region = region;
		this.bucket = bucket;
		this.useS3TransferAcceleration = useS3TransferAcceleration;

	public void configure() {

You may add another enum like this:

DEV("companydev", "eu-west-1", "companydev-deployment", true);

In order to handle you DEV environment and account.

Use of S3 Accelerated Transfer

The last parameter in the Aws constructor is the boolean useS3TransferAcceleration. It is so useful for reducing your deployment time that it is true by default but this can cause an increase in your AWS billing.

As you see, this code is using the class AwsProfileRegionClientConfigurator available from dependency:

Remove the scope test

You may need to remove the scope test in case you are using the AwsProfileRegionClientConfigurator inside src/main/java.

Then you will be able to use this configuration in your tests with Aws.PROD.configure(), like it is done in provided test in class UploadAndUpdateLambda:



import org.junit.Test;


public class UploadAndUpdateLambda {

	public void process() {

	 	File file = new File("target/");
	 	String bucket = Aws.DEPLOYMENT_BUCKET;
	 	String s3key = S3Utils.uploadFileToS3(file, bucket, 20);

	 	LambdaUtils.updateLambdaCode(new String[] {"XXXLambda"}, bucket, s3key);

2.3. From the Java Lambda code

When the Lambda code is deployed to a lambda, the credentials and the region must not be precised as it is deduced from the AWS Region where you have deployed your Lambda.

Nevertheless, it may be very useful to be able to run your Lambda code on your development machine targeting different profiles while your Lambda code stay independent from the profile/region.

The solution is to use this way of instanciating the AWS Clients:

  • For S3

S3Client s3Client = AwsProfileRegionClientConfigurator.getInstance().configure(S3Client.builder()).build();
  • For DynamoDB

DynamoDbClient dynamoDbClient = AwsProfileRegionClientConfigurator.getInstance().configure(DynamoDbClient.builder()).build();

I suggest to use the class [package].aws.AwsClients where you can put all your AWS Clients.

All the AWS Clients are Threadsafe

As the creation of an AWS client has a cost, it is very useful to create your AWS Clients as singletons (static). In that case, you need to verify that Aws.PROD.configure() will occur before the initialization of your AWS clients, for example in a static block before the static fields.

2.4. For the AWS SAM CLI

At the root of the project, you can find the AWS SAM config file: samconfig.toml

Inside the file, you can set the profile and the region:

profile = "companydev"
region = "eu-west-1"

2.5. For the AWS CDK CLI

At the root of the project, you can find the AWS CDK config file: cdk.json

Inside the file, you can set the profile:

  "app": "mvn -e -q compile test -Dtest=xxx.devops.cdk.CreateApp",
  "watch": {
    "include": [
    "exclude": [
  "context": {
    "@aws-cdk/aws-apigateway:usagePlanKeyOrderInsensitiveId": true,
    "@aws-cdk/core:stackRelativeExports": true,
    "@aws-cdk/aws-rds:lowercaseDbIdentifier": true,
    "@aws-cdk/aws-lambda:recognizeVersionProps": true,
    "@aws-cdk/aws-cloudfront:defaultSecurityPolicyTLSv1.2_2021": true,
    "@aws-cdk-containers/ecs-service-extensions:enableDefaultLogDriver": true,
    "@aws-cdk/core:target-partitions": [
  "profile": "companydev"

2.6. From the AWS CDK code

The AWS CDK code is using the Environment class, configured with the account_id and the region.

Microlam is providing the method StsUtils.getAccountId() that gets the AWS account_id from the current configured profile (with Aws.configure()):

String account_id = StsUtils.getAccountId();

Environment env = Environment.builder()

See complete code in Class xxx.devops.cdk.CreateApp in src/test/java.

3. Using Microlam Parameters for AWS

Most of our applications depends on secrets or parameters you prefer to keep externally from your code. AWS is providing a service for that (System Manager / Parameter Store) you can leverage easily with Microlam.

Microlam quickstart project is now including the class [package].params.SystemParameters you

3.1. Maven configuration

The Microlam Parameters for AWS library is provided by this maven dependency:


3.2. Usage

Your entry point is the class ParameterStoreProviderPath taking in its constructor as first argument the prefix of all the parameters.

Example of usage:

package tech.solusoft.params;

import io.microlam.utils.params.AttributesProvider;

public class SystemParameters {

	public static final AttributesProvider ATTRIBUTES_PROVIDER = new ParameterStoreProviderPath("/PREFIX");

	private static String PRIVATE_KEY = null;
	private static String FIREBASE_SECRET = null;

	public static String FIREBASE_SECRET() {
		if (FIREBASE_SECRET == null) {

	public static String PRIVATE_KEY() {
		if (PRIVATE_KEY == null) {
		return PRIVATE_KEY;


When using prefix "/PREFIX" and retrieving value "PRIVATE_KEY" with method getStringValue() to access attribute whose full path is "/PREFIX/PRIVATE_KEY".

The second argument to method getStringValue() is a default value or null if you don’t want to provide one.

3.3. AWS needed permissions

You need to provide access to the relevant used path:

    "Version": "2012-10-17",
    "Statement": [
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
            "Resource": [

4. Using the Microlam DynamoDB Helper

The Microlam DynamoDB Helper includes several features:

  • Create DynamoDB requests easily without the need of checking / escaping reserved key words

  • Construct programmatically ConditionExpression without concatenating String

  • Map DynamoDB objects to json and vice-versa.

  • Help you generate partial response from multiple queries by transmitting a lastkey String attribute to your client: Using the query pipeline.

4.1. Maven configuration

The Microlam DynamoDB Helper is provided by this maven dependency:


4.2. DynamoDB Client

You can use a Singleton with lazy instanciation to give access to the client from anywhere in your project, for example, defining the class AwsClients :

public abstract class AwsClients {

	protected static DynamoDbClient dynamoDbClient = null;

	public static DynamoDbClient getDynamoDbClient() {
		if (dynamoDbClient == null) {
			dynamoDbClient = createDynamoDbClient();
		return dynamoDbClient;

	private static DynamoDbClient createDynamoDbClient() {
		return AwsProfileRegionClientConfigurator.getInstance().configure(DynamoDbClient.builder()).build();

4.3. PutItem request

Just use the helper builder PutItemRequestBuilder as in this example:

import static io.microlam.dynamodb.expr.ConditionExpression.or;
import static io.microlam.dynamodb.expr.ConditionExpression.attributeNotExists;

public static boolean putItemExample() {
	 	PutItemRequestBuilder request = PutItemRequestBuilder.builder()
			.item(DynamoDBHelper.createAttributeValueMap("PK1", "pk1", "SK1", "sk1", "firstName", "Frank"))
			.conditionExpression(or(attributeNotExists("PK1"), attributeNotExists("SK1")));
	 	PutItemResponse response = AwsClients.putItem(;
		return response.sdkHttpResponse().isSuccessful();
DynamoDBHelper & ConditionExpression & Operand are your main entry points in the library
  • DynamoDBHelper let you create an AttributeValueMap or update it among other things. This is the main entry point in the API.

  • ConditionExpression will give you access to all the available functions.

  • Operand will give you access to all the available values

4.4. GetItem request

Just use the helper builder GetItemRequestBuilder as in this example:

public static String findConnectionId(String public_key) {
	GetItemRequestBuilder builder = GetItemRequestBuilder.builder()
			.partitionKey("PK", public_key)
	GetItemResponse response = AwsClients.getDynamoDbClient().getItem(;
	if (response.hasItem()) {
		return response.item().get("connection_id").s();
	else {
		return null;

4.5. UpdateItem request

Just use the helper builder UpdateItemRequestBuilder as in this example:

public static void updatePseudo(String PK, String SK, String pseudo) {
		long currentTime = System.currentTimeMillis();
		UpdateItemRequest updateItemRequest = UpdateItemRequestBuilder.builder()
			.partitionKey("PK", PK)
			.sortKey("SK", SK)
					AssignmentExpression.create("pseudo", Operand.stringValue(pseudo)),
					AssignmentExpression.create("updating_date", Operand.numberValue(currentTime)),
					AssignmentExpression.create("creation_date", Operand.ifNotExists("creation_date", Operand.numberValue(currentTime)))
		UpdateItemResponse responce = AwsClients.getDynamoDbClient().updateItem(updateItemRequest);

4.6. DeleteItem request

Just use the helper builder DeleteItemRequestBuilder as in this example:

public static void deleteEntity(String PK, Entity entity) {
	DeleteItemRequestBuilder builder = DeleteItemRequestBuilder.builder()
			.partitionKey("PK", PK)
	DeleteItemResponse response = AwsClients.getDynamoDbClient().deleteItem(;

4.7. Query request

Just use the helper builder QueryRequestBuilderBuilder as in this example:

public static Map<String,AttributeValue> findUserReport(String report_id) {
	QueryRequestBuilderBuilder builder = QueryRequestBuilderBuilder.builder()
					ConditionExpression.comparison(Operand.attributePath("PK2"), ComparatorOperator.EQUAL, Operand.stringValue(report_id)),
					ConditionExpression.comparison(Operand.attributePath("SK2"), ComparatorOperator.EQUAL, Operand.stringValue(;
	QueryResponse response = AwsClients.getDynamoDbClient().query(;
	if (response.hasItems() && response.items().size() > 0) {
		return response.items().get(0);
	else {
		return null;

4.8. Scan request

Just use the helper builder ScanRequestBuilderBuilder as in this example:

public void testScanRequest() {
	ScanRequest.Builder requestBuilder = ScanRequestBuilderBuilder.builder()
		.projectionPaths("email", "PK1", "SK1")

	ScanResponse response;
	do {
		response = AwsClients.getDynamoDbClient().scan(;
		for(Map<String, AttributeValue> item: response.items()) {
	while (! response.lastEvaluatedKey().isEmpty()) ;

4.9. Using the request pipeline

The Request pipeline allows you to execute several requests in order and to retrieve a given max number items and gives you a String token to continue the requests where you left of.

You may include several QueryRequest and ScanRequest in the RequestPipeline.

The BasicRequestPipeline constructor takes 2 parameters:

  • The DynamoDb client

  • A list of GenericRequestBuilder

Where a GenericRequestBuilder may be of 2 sort:

  • QueryGenericRequestBuilder for encapsulating a query name and a QueryRequest.Builder

  • ScanGenericRequestBuilder for encapsulating a query name and a ScanRequest.Builder

On the third argument of QueryGenericRequestBuilder or ScanGenericRequestBuilder constructor you need to provide the List of attibute names used as primary partitionKey and sortKey of the table you query and also the eventual partitionKey and sortKey of the index you query.

When your RequestPipeline is built you can use it for:

  • Getting the number of items to process

  • Process the items

Then you can process your RequestPipeline with an ItemProcessor and a limit as max items count (where -1 is used for no limit) and an eventual lastKeyString that may be null for starting the Pipeline from the first available item.

This is an example:

QueryRequest.Builder queryBuilder1 = xxxx; // Build your query
QueryGenericRequestBuilder query1 = new QueryGenericRequestBuilder("query1", queryBuilder1, "PK", "SK", "IN");

ScanRequest.Builder scanRequest1 = xxxx; //Build your query
ScanGenericRequestBuilder scan1 = new ScanGenericRequestBuilder("scan1", scanRequest1, "PK", "SK");

List<GenericRequestBuilder> requests = new ArrayList<>();
BasicRequestPipeline basicRequestPipeline = new BasicRequestPipeline(client, requests);

int limit = 50;
String lastKey = null;

//Get total number of items to process
int totalNumberOfItems = basicRequestPipeline.count(-1, lastKey);
System.out.println("totalNumberOfItems: " + totalNumberOfItems);

//Process the items by pack of 50
GenericPipelineResult result = basicRequestPipeline.process(new ItemProcessor() {

	public void process(String requestName, Map<String, AttributeValue> item) {
		//Process the item coming from the request named 'requestName'
}, limit, lastKey);

System.out.println("processCount: " + result.processCount);
System.out.println("lastKey: " + result.lastKeyString);

As you can see, you get a GenericPipelineResult as a return value for the processing, where you can find:

  • the processCount where you can check the number of items returned to the ItemProcessor.

  • the lastKeyString giving you a String you can use to continue the processing.

4.10. Json and DynamoDB

The class DynamoDBHelper contains several convert methods you can use for converting from/to Json to/from AttributeValue.

Note that there may be several possibilities for converting a Json List to a DynamoDB AttributeValue as you may convert it not only to a DynamoDBType.List but also to a DynamoDBType.StringSet, DynamoDBType.NumberSet or DynamoDBType.BinarySet…​

That’s why you may provide a Json metadata object to the DynamoDBHelper.convert() method containing the given Map of JsonPath String to the required DynamoDBType name:

	"$.example.test" : "StringSet"

In this example the attribute example.test (attribute test inside attribute example) from the root of the json is mapped to the DynamoDBType type StringSet.

You can also generate a Json metadata object from a given AttributeValue with the help of the method DynamoDBHelper.metadata().

5. Microlam AWS Devops support

Microlam is providing a small library with very useful functions for devops. Microlam archetype project is also already configured for using AWS SAM or AWS CDK (which is is recommended).

5.1. Maven configuration

The Microlam DynamoDB Helper is provided by this maven dependency:


5.2. Usage

There are 3 handy classes you can use:

  • S3Utils related to AWS S3 utilities

  • LambdaUtils related to AWS Lambda utilities

  • StsUtils related to AWS STS utilities (for now, giving you only access to your AWS account id)

For example, see the generated class UploadAndUpdateLambda, allowing you to update your Lambdas from your AWS deployment zip:



import org.junit.Test;


public class UploadAndUpdateLambda {

	public void process() {

	 	File file = new File("target/");
	 	String bucket = Aws.DEPLOYMENT_BUCKET;;
	 	String s3key = S3Utils.uploadFileToS3(file, bucket, 20); //file.getName();//

	 	LambdaUtils.updateLambdaCode(new String[] {"XxxLambda"}, bucket, s3key);

Note that the method S3Utils.uploadFileToS3() is using multi-threading (you configure the number of threads) for uploading your file. This should increase significally your productivity !

5.3. AWS Native compilations tips

The AWS java SDK 2.x is including an http client that you need to exclude in order to not depend on Apache client, Netty framework and another version of SLF4J which gives difficulties for GraalVM native compilation. Fortunately, AWS provide a way to configure the client you want to use and you can exclude the problematic libraries.

This is how you should include an AWS Java SDK dependency:


Then you provide this as the default http client to use:


unfortunately, this client is not supporting all devops operations (s3 multi threads upload) so you must also add this dependency for tests:


As a consequence when you run a test, the Java AWS SDK will find 2 possible implementations for an HTTP client and will complain with this exception: Multiple HTTP implementations were found on the classpath. To avoid non-deterministic loading implementations, please explicitly provide an HTTP client via the client builders, set the system property with the FQCN of the HTTP service to use as the default, or remove all but one HTTP implementation from the classpath

Which you can solve by adding this parameter when running a test/devops code:

6. Feedback

Microlam is only beginning and needs your feedback and your help to improve.

If you have any questions or need some support, click here.