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Write Your AWS Lambda Functions in Java

AWS Lambda is an Amazon Web Services compute service that makes it easy for you to build applications that respond quickly to new information. AWS Lambda runs your code in response to specific events. It is up to you to choose the type of events, however, here are some examples of the kinds of events that could be made to trigger a Lambda function:

  • Image uploads
  • In-app activity; website clicks
  • Output from connected devices
  • Product purchases

AWS Lambda can be used to extend other AWS services with custom logic. You can even use it to create a dynamic back-end that operates at AWS scale, performance, and security. Not only that, you can easily create discrete, event-driven applications that execute only when needed and scale automatically from a few requests per day to thousands per second.

AWS Lambda works by running your code on a high-availability compute infrastructure and performs all the administration of the compute resources, which includes:

  • Server and operating system maintenance
  • Capacity provisioning and automatic scaling
  • Code and security patch deployment
  • Code monitoring and logging

What’s changed with AWS Lambda

Up until one week ago, the only solution available for developers to write their Lambda functions was in Node.js, which is a JavaScript derivative specifically designed for use in server-side applications. However,  AWS announced that you can now write your Lambda functions in Java.

AWS also has plans to continue adding language options for Lambda functions sometime in the near future. Naturally, all of our existing development tools can of course still be used.

If you are already familiar with uploading Node.js deployment packages to Lambda, you will already know that they are limited to fifty MB. This limit will be true for your Java code as well. Some other things that you need to be aware of if you intend to utilize this new functionality include:

  • You must create a ZIP or JAR file that contains your compiled code (CLASS files) and any desired JAR files.
  • Your handler functions should be stored in the usual Java directory structure (e.g.com/mypackage/MyHandler.class).
  • Your JAR files must be directly inside of a lib subdirectory.
  • You must specify a runtime of “java8″ when you upload your ZIP file.
  • If you implemented one of the handler interfaces, you will need to provide the class name, or otherwise, provide the fully qualified method reference, like:
    com.mypackage.LambdaHandler::functionHandler

AWS Lambda and Cloud Academy

If you’re not yet that familiar with Lambda, Cloud Academy has some excellent learning resources to help:

Cloud Academy’s Understanding AWS Lambda course provides a complete introduction to AWS Lambda. Lambda is not a particularly complex service, but setting IAM roles and security groups might be tricky. This tutorial, written by our expert Cloud Solutions Architect Kevin Felitchko, will help you get started, and provide an interesting and practical use-case.

Cloud Academy also has a hands-on lab on Automated static site generation using AWS S3 and Lambda. This intermediate-level lab will guide you through the steps necessary to process content, host it on S3, and manage Lambda’s access to your other AWS resources.

We’ve also got a set of self-testing questions in our Lambda Quiz to help you assess your overall understanding of the service.

Further Reading

The Official AWS Announcement
Authoring Lambda Functions in Java

Written by

Michael Sheehy

I have been UNIX/Linux System Administrator for the past 15 years and am slowly moving those skills into the AWS Cloud arena. I am passionate about AWS and Cloud Technologies and the exciting future that it promises to bring.

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