Working With AWS Lambda Java Functions: 6 Easy Steps

Companies regularly need to update their applications for smooth functioning and implementation of new features. Developers continuously work on making the applications fast, smooth and secure. Modern applications use serverless and Cloud technologies For this, it is essential to have hands-on versatile programming languages such as Java. 

Java is a high-level programming language widely used in the majority of enterprise applications and backend services for running business activities. Using serverless computing services in applications such as AWS Lambda improves applications’ performance significantly. AWS Lambda Java projects are easy to build and manage.

AWS Lambda Java functions can be created on Eclipse IDE and run via uploading it to the AWS Lambda. In this article, you will learn about the steps to create, upload and invoke the AWS Lambda Java functions with an example.

Introduction to AWS Lambda

AWS Lambda is the compute service offered by Amazon Web Services that allows you to without managing any server. It is an event-driven and serverless computing platform that runs code in response to events. AWS Lambda officially supports Python, Node.js Java, Go, Ruby, and C# language.

AWS Lambda uses a serverless computing service that executes Lambda functions to perform any computing task from serving web pages and processing data streams.

Key Features of AWS Lambda

Some of the main features of AWS Lambda are listed below:

• Fault-tolerance: AWS Lambda helps users protect their code against individual machine or data center facility failures by maintaining compute capacity across multiple Availability Zones.
• Auto-Scaling: AWS Lambda can automatically scale for supporting the rate of incoming requests and invoking the code only when needed.
• Flexible Resource Model: Users can choose the amount of memory they want to allocate to functions and it will CPU power, network bandwidth, and disk input/output (I/O) proportionally.
• Automated Administration: AWS Lambda is capable of managing all the infrastructure for you to run your code and help you focus more on building backend services.

What is Java?

Java is a class-based, high-level, and object-oriented programming language first released by Sun Microsystems in 1995. Programmers can write code in Java once and run it anywhere because Java code runs on all platforms that support Java without the need to recompile.

Java is used for building most applications because it is scalable and fast. It uses Java Virtual Machine to compile code to bytecode which makes it independent of computer architecture.

Key Features of Java

Some of the main features of using Java are given below:

• Platform Independent: Java compiles into platform-independent byte code instead of a platform-specific machine that allows users to run single code on any platform.
• Multithreaded: Java is capable of executing multiple tasks simultaneously which makes it easier for Developers to build an application to run smoothly.
• Easy to Use: Java is a simple and easy-to-learn programming language that follows OOPs concepts and logic.

Running AWS Lambda Java Funcion

Now that you have understood the AWS Lambda and Java language. In this section, you will learn about the procedure and steps to create, upload and invoke an AWS Lambda Java function. For creating AWS Lambda Java functions you need to have an AWS account and AWS Toolkit for Eclipse installed. The following steps for working with the AWS Lambda Java function are listed below:

• Step 1: Creating an AWS Lambda Project
• Step 2: Implementing the Handler Method
• Step 3: Creating an IAM Role for AWS Lambda Java Project
• Step 4: Creating AWS S3 Bucket
• Step 5: Uploading the AWS Lambda Java Code
• Step 6: Invoking the AWS Lambda Java Function

Step 1: Creating an AWS Lambda Project

• First, you need to implement the code as a method in a handler class. 
• Open Eclipse and from the toolbar, open the Amazon Web Services menu (homepage icon). 
• Click on the “New AWS Lambda Java project” option.
• Or you can also go to the Eclipse menu bar and there choose “AWS Lambda Java Project” from the “File Menu“.
• Now, you have to provide the Project name, Group ID, Artifact ID, and class name for the AWS Lambda Java function project, as shown in the image below.

• For this tutorial, the following details are used listed below.
  • Project name: HelloLambda
  • Group ID: com.example.lambda
  • Artifact ID: demo
  • In the “Package Name” field, you need to provide the AWS Lambda handler class. By default, it automatically fills with the concatenation of Group ID and Artifact ID.
  • In the “Input Type” drop-down menu, choose the “Custom” option.
  • Then, click on the “Finish” button.
  • The source code and the project’s directory will automatically be generated in the Eclipse Workspace.
  • A new browser window will open up with “README.html” providing the instructions to guide how to implement, test, upload and invoke the AWS Lambda Java function.

Step 2: Implementing the Handler Method

• Now, let’s implement the AWS Lambda Java function in the “HelloLambda” project created. 
• In the “Project Explorer” of Eclipse, open up the “Hello.java” file. 
• It has the similar code given below.

package com.example.lambda.demo;

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.RequestHandler;

public class Hello implements RequestHandler<Object, String> {

    @Override
    public String handleRequest(Object input, Context context) {
        context.getLogger().log("Input: " + input);

        // TODO: implement your handler
        return "Hello from Lambda";
    }

}

• Now, replace the contents of the “handleRequest” function with the code given below.

@Override
public String handleRequest(String input, Context context) {
  context.getLogger().log("Input: " + input);
  String output = "Hello, " + input + "!";
  return output;
}

Step 3: Creating an IAM Role for AWS Lambda Java Project

• Sign in to your AWS Management Console here.
• Now, open the “IAM Console” from the “Services” menu.
• From the navigation panel, choose the “Roles” option and select the “Create role” option.
• Now, in the “Select type of trusted entity” drop-down menu, choose the “AWS service” option. 
• Then, choose the “Lambda” option for the service that will use this role.
• Click on the “Next: Permissions” option.
• From the “Attach permissions policy” drop-down menu, choose the “AWSLambdaBasicExecutionRole” option. 
• Then, click on the “Next: Review” button.
• Now, add a name for the role like for this AWS Lambda Java project, the name is “hello-lambda-role” and describe the role.
• Next, click on the “Create role” button to create an IAM role for the AWS Lambda Java project.

Step 4: Creating AWS S3 Bucket

• To store your AWS Lambda Java project, you need AWS S3 Bucket for uploading. 
• If you already have an AWS S3 bucket then you can use that or create a new one, especially for the AWS Lambda Java function.
• Go to AWS Management Console and there open the “S3 Console” from the “Services” menu.
• Click on the “Create bucket” option.
• Now, provide the valid details to create an S3 bucket for your AWS Lambda Java project such as bucket name, region, etc.
• Click on the “Create” button to create an AWS S3 Bucket.

Step 5: Uploading the AWS Lambda Java Code

• Now, right-click on the Eclipse Window and then choose the “AWS Lambda” option. There select the “Upload function to AWS Lambda“.
• Navigate to the “Select Target Lambda Function” page and select the region to use. Note that this location should be the same as the location of the AWS S3 Bucket, as shown in the image below.

• Choose the “Create a new Lambda function” option and provide a name for your function such as HelloFunction.
• Click on the “Next” option.
• Describe your target AWS Lambda Java function on the “Function Configuration” page, as shown in the image below.

• Then, choose the IAM role and AWS S3 Bucket for your AWS Lambda Java function.
•  Click on the “Function Role” option and select the “Create” option for creating a new IAM role for your AWS Lambda Java function.
• Provide the “Role Name” of your choice, as shown in the image below.

• In the “S3 Bucket for Function Code” provide the Bucket Name, as shown in the image below.

• Here, you can also choose to encrypt the uploaded code. In this AWS Lambda Java project, you can choose the “None” option.
• Click on the “Finish” button to upload your AWS Lambda Java function.
• If the upload of AWS Lambda Java code is successful then, you will see the AWS Lambda Java function name next to your Java handler class in the “Project Explorer” view, as shown in the image below.

Step 6: Invoking the AWS Lambda Java Function

• Now, right-click on the Eclipse code window, here go to the “AWS Lambda” option and then select the “Run Function on AWS Lambda” option.
• Then, you will be asked to choose the handler class that you want to invoke.
• Here, now provide a valid JSON String such as “AWS Lambda” in the input field, as shown in the image below.

• Click on the “Invoke” button to send your input data to the AWS Lambda Java function.
• After following the procedure correctly, you can see the return value or the response of your AWS Lambda Java function in the “Console” view of the Eclipse, as shown in the image below.

That’s it! You have successfully created, uploaded, and invoked your AWS Lambda Java function.

Conclusion 

In this article, you learnt about AWS Lambda and went through the steps to how to create, upload and invoke AWS Lambda Java functions. You used AWS S3 Bucket for uploading the AWS Lambda Java code from Ecplise and managed IAM roles for your AWS Lambda Java project. AWS Lambda helps Developers automatically manage the computing resources required by the code. AWS S3 Bucket is widely used as a storage space for data needed by applications and backend services.

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