Migrating Your Java Aplication from Tomcat to AWS Lambda: A Step-by-Step Guide


When it comes to serverless architechture, AWS Lambda is a real game changer. This article will walk you through the process of migrating a Java application from Tomcat to AWS Lambda. We will cover every aspect of the migration process, from the very basic setup to the more advanced customization. By the end of this article, you’ll be fully equiped with the knowledge you need to make the transition smoothly. Let’s get started!

1. Understanding AWS Lambda and Serverless Architecture

AWS Lambda is a powerful service provided by Amazon Web Services that allows you to run your code in a serverless environment. The benifits of this are numerous, including cost savings, reduced overhead, and improved scalibility. With AWS Lambda, you pay only for the actual compute time you use, making it an attractive option for many applications.

2. Preparing Your Java Application for Migration

Before we dive into the actual migration, there are some preparatory steps you need to take to ensure your Java application is ready for the transition.

a. Analyze your Java application’s code

First, you will need to identify the parts of your application that can be migrated to AWS Lambda. Not all Java applications can be easily converted to Lambda functions, as they might rely on features that are not supported in a serverless environment. For example, if your Java application makes use of long-running processes, it maynot be a good candidate for AWS Lambda. On the other hand, if your application is stateless, event-driven, and has a short execution time, it should be well-suited for AWS Lambda.

b. Refactor your code

Once you’ve identified the parts of your Java application that can be migrated to AWS Lambda, you’ll need to refactor the code to fit the AWS Lambda model. You might need to break down your code into smaller, self-contained functions. This is because Lambda functions are designed to execute in response to specific events, such as an API call, a file upload, or a database trigger.

c. Choose the right runtime

AWS Lambda supports multiple runtimes, including Java. You’ll need to select the appropriate runtime for your Java application. Keep in mind that AWS Lambda supports only specific versions of Java, so make sure your application is compatible with the supported versions.

3. Setting Up Your AWS Environment

To migrate your Java application to AWS Lambda, you’ll need to set up an AWS account and configure the necessary services.

a. Create an AWS account

If you don’t already have an AWS account, you can sign up for one at the AWS website. Follow the on-screen instructions to complete the registration process.

b. Install and configure the AWS CLI

The AWS Command Line Interface (CLI) is a powerful tool for managing your AWS services. You can download and install the AWS CLI from the official AWS website. Once you’ve installed the AWS CLI, you’ll need to configure it with your AWS account credentials. You can do this by running the following command:

aws configure

Enter your AWS Access Key ID, Secret Access Key, and desired AWS region when prompted.

c. Set up an S3 bucket

AWS Lambda requires an S3 bucket to store your Java application’s code. To create a new S3 bucket, run the following command:

aws s3api create-bucket --bucket your-bucket-name --region your-region

Replace “your-bucket-name” with a unique name for your bucket, and “your-region” with the desired AWS region.

4. Deploying Your Java Application to AWS Lambda

Now that your AWS environment is set up, it’s time to deploy your Java application to AWS Lambda.

a. Package your Java application

You’ll need to package your Java application into a JAR or ZIP file. To do this, use the following command:

mvn clean package

This will create a JAR or ZIP file in your project’s “target” directory.

b. Upload your Java application to S3

Next, you need to upload the packaged Java application to the S3 bucket you created earlier. To do this, run the following command:

aws s3 cp target/your-application.jar s3://your-bucket-name/your-application.jar

Replace “your-application.jar” with the name of your JAR or ZIP file, and “your-bucket-name” with the name of your S3 bucket.

c. Create a Lambda function

Now you’ll create the Lambda function that will execute your Java application. To do this, run the following command:

aws lambda create-function --function-name your-function-name --runtime java8 --handler your-handler --role your-role-arn --code S3Bucket=your-bucket-name,S3Key=your-application.jar

Replace “your-function-name” with a unique name for your Lambda function, “your-handler” with the fully-qualified name of your Java handler class, “your-role-arn” with the ARN of the AWS IAM role that grants permissions to your Lambda function, and “your-bucket-name” and “your-application.jar” with the corresponding values.

d. Test your Lambda function

After creating your Lambda function, you should test it to ensure that it’s working correctly. You can do this by invoking the function using the AWS CLI:

aws lambda invoke --function-name your-function-name --payload '{"key1": "value1"}' output.txt

This will execute your Lambda function with a sample payload and write the output to a file named “output.txt”. Check the contents of “output.txt” to verify that your Lambda function is working as expected.

5. Integrating with API Gateway

For your Java application to be accessible over the internet, you’ll need to set up an API Gateway to route incoming requests to your Lambda function.

a. Create an API Gateway

To create a new API Gateway, run the following command:

aws apigateway create-rest-api --name your-api-name

Replace “your-api-name” with a unique name for your API Gateway.

b. Create a resource and method

Next, create a resource and method for your API Gateway. This will define the URL path and the HTTP method (e.g., GET or POST) for accessing your Lambda function. To do this, run the following commands:

aws apigateway create-resource --rest-api-id your-rest-api-id --parent-id your-parent-id --path-part your-path-part

aws apigateway put-method --rest-api-id your-rest-api-id --resource-id your-resource-id --http-method your-http-method --authorization-type "NONE"

Replace “your-rest-api-id”, “your-parent-id”, “your-path-part”, “your-resource-id”, and “your-http-method” with the appropriate values.

c. Integrate your Lambda function with API Gateway

Now, you’ll need to integrate your Lambda function with the API Gateway. To do this, run the following command:

aws apigateway put-integration --rest-api-id your-rest-api-id --resource-id your-resource-id --http-method your-http-method --type AWS_PROXY --integration-http-method POST --uri arn:aws:apigateway:your-region:lambda:path/2015-03-31/functions/your-function-arn/invocations

Replace “your-rest-api-id”, “your-resource-id”, “your-http-method”, “your-region”, and “your-function-arn” with the appropriate values.

d. Deploy your API Gateway

Finally, deploy your API Gateway to make it publicly accessible. To do this, run the following command:

aws apigateway create-deployment --rest-api-id your-rest-api-id --stage-name your-stage-name

Replace “your-rest-api-id” and “your-stage-name” with the appropriate values.

6. Migrating Databases and Other Dependencies

If your Java application relies on a database or other external dependencies, you’ll need to migrate these as well. For example, you might need to migrate your existing database to Amazon RDS or DynamoDB. Keep in mind that migrating databases and other dependencies can be a complex process, so it’s essential to plan and test your migration carefully.


In this article, we’ve covered the step-by-step process of migrating a Java application from Tomcat to AWS Lambda. By following these steps, you’ll be able to enjoy the benifits of serverless architecture and take advantage of the many features offered by AWS Lambda. Good luck with your migration, and don’t forget to keep experimenting with AWS Lambda to discover new ways to optimize your Java application’s performance.

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