BoxLang on AWS Lambda

Overview

The BoxLang AWS Runtime provides a pre-built Java handler for serverless Lambda functions. You write BoxLang classes; the runtime handles request/response lifecycle, serialization, logging, and error management.

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Handler Configuration

Set this as your Lambda handler in AWS:

ortus.boxlang.runtime.aws.LambdaRunner::handleRequest

The runtime automatically:

• Deserializes the incoming JSON event into a BoxLang Struct
• Calls your Lambda.bx class run() method
• Serializes the return value back to JSON
• Manages error handling and logging

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Lambda.bx Convention

The runtime looks for Lambda.bx in your deployment package root and calls run():

class {

    /**
     * The main Lambda handler function.
     *
     * @param event    The incoming event struct (deserialized from JSON)
     * @param context  The AWS Lambda context object (Java LambdaContext)
     * @param response A pre-built response struct you can populate:
     *                 { statusCode: 200, body: "", headers: {} }
     */
    function run( event, context, response ){
        // Simple return value — auto-serialized to JSON
        return {
            statusCode: 200,
            body: {
                message: "Hello from BoxLang Lambda!",
                input:   event
            }
        }
    }

}

Response Convention

You can either return a value or populate the response struct:

function run( event, context, response ){
    // Option 1: return a value (auto-serialized)
    return { statusCode: 200, body: "OK" }

    // Option 2: populate response struct
    response.statusCode = 200
    response.body       = serializeJSON({ message: "Done" })
    response.headers    = { "Content-Type": "application/json" }
}

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Application Lifecycle (Application.bx)

Place Application.bx in your deployment package for lifecycle hooks:

class {
    this.name = "MyLambda"

    // Called once on cold start — initialize resources here
    boolean function onApplicationStart(){
        application.db = createObject("component","DataService").init()
        return true
    }

    // Called on every request before run()
    boolean function onRequestStart( required string targetPage ){
        return true
    }
}

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Project Structure (Starter Template)

Use the official starter: https://github.com/ortus-boxlang/boxlang-starter-aws-lambda

/src
  /main
    /bx
      Application.bx     -- Lifecycle class
      Lambda.bx          -- Your Lambda handler
    /resources
      boxlang.json        -- BoxLang runtime config
      boxlang_modules/    -- Installed BoxLang modules
  /test
    /java
      /com/myproject
        LambdaRunnerTest.java   -- Integration tests
        TestContext.java
        TestLogger.java
/workbench
  config.env              -- Default env config
  config.local.env        -- Local overrides (gitignored)
  sampleEvents/           -- Test event payloads (.json files)
  template.yml            -- SAM template for local testing + deploy
  *.sh                    -- Deploy/management scripts
/box.json                 -- BoxLang module dependencies
/build.gradle             -- Build config (shaded JAR)

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Environment Variables

Variable	Description
BOXLANG_LAMBDA_CLASS	Absolute path to Lambda class. Default: /var/task/Lambda.bx
BOXLANG_LAMBDA_DEBUGMODE	Enable debug mode + performance metrics (true/false)
BOXLANG_LAMBDA_CONFIG	Path to custom boxlang.json. Default: /var/task/boxlang.json
BOXLANG_LAMBDA_CONNECTION_POOL_SIZE	Database connection pool size. Default: 2
LAMBDA_TASK_ROOT	Lambda deployment root. Default: /var/task

Any BOXLANG_* env variable also maps to boxlang.json config overrides.

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Performance Enhancements

Class Compilation Caching

Lambda classes are compiled and cached on the first (cold start) invocation. Warm invocations reuse the cached bytecode — no re-compilation overhead.

Disable caching in development (debug mode):

BOXLANG_LAMBDA_DEBUGMODE=true

Connection Pooling

Database connections are pooled and reused across warm invocations:

BOXLANG_LAMBDA_CONNECTION_POOL_SIZE=5

Cold Start Optimization Tips

1. Use Application.bx onApplicationStart() to initialize shared resources
2. Minimize modules loaded at startup — only install what you use
3. Use the asm compiler (default) for better startup performance
4. Set storeClassFilesOnDisk: true in boxlang.json

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Multiple Lambda Functions (URI Routing)

Use the x-bx-function header to call a specific method on the class:

# Calls Lambda.bx run() method (default)
curl https://api.example.com/function

# Calls Lambda.bx processOrder() method
curl -H "x-bx-function: processOrder" https://api.example.com/function

In Lambda.bx:

class {

    function run( event, context, response ){
        return { message: "Default handler" }
    }

    function processOrder( event, context, response ){
        return orderService.process( event )
    }

    function getUsers( event, context, response ){
        return userService.list( event.limit ?: 20 )
    }

}

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Local Development with SAM CLI

# Install AWS SAM CLI
# https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html

# Start local Lambda API
sam local start-api --template workbench/template.yml

# Invoke a specific function locally
sam local invoke BoxLangFunction --event workbench/sampleEvents/test-event.json

# Build the shaded JAR (includes all dependencies)
./gradlew shadowJar

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Deploying to AWS

# Configure AWS credentials first
aws configure

# Build, package, and deploy via SAM
./gradlew shadowJar
sam deploy --guided --template workbench/template.yml

# Or use the included deploy scripts
chmod +x workbench/*.sh
./workbench/deploy.sh

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BoxLang Modules in Lambda

Install modules to the src/main/resources/boxlang_modules/ directory using CommandBox:

# Install a module to the Lambda module directory
box install bx-mail --boxlang-home=src/main/resources

# The module will be zipped with the deployment package

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Production Checklist

•  Application.bx initializes shared resources (connections, config) in onApplicationStart()
•  BOXLANG_LAMBDA_DEBUGMODE=false in production
•  Connection pool size tuned: BOXLANG_LAMBDA_CONNECTION_POOL_SIZE
•  Secrets via AWS SSM Parameter Store or Secrets Manager, injected as env vars
•  boxlang.json present in deployment package root
•  Lambda timeout set generously for cold starts (30s+ recommended)
•  Memory allocation ≥ 512MB (1024MB+ for better performance)
•  Integration tests passing via ./gradlew test