AWS: Java S3 Lambda Handler

If you want to write a Lambda for AWS in Java that connects to S3. You need to have the handler.

Maven:

<dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-java-sdk</artifactId>
    <version>1.11.109</version>
</dependency>

This is the method that AWS Lambda will call. It will look similar to the one below.

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.services.lambda.runtime.events.S3Event;
import com.amazonaws.services.s3.event.S3EventNotification.S3Entity;
import com.amazonaws.services.s3.event.S3EventNotification.S3EventNotificationRecord;
 
public void S3Handler(S3Event s3e, Context context) {
	final String awsRequestId =  context.getAwsRequestId();
	final int memoryLimitMb = context.getMemoryLimitInMB();
	final int remainingTimeInMillis = context.getRemainingTimeInMillis();
 
	for (final S3EventNotificationRecord s3Rec : s3e.getRecords()) {
		final S3Entity record = s3Rec.getS3();
		
		final String bucketName = record.getBucket().getName()
		final String key = record.getObject().getKey();
	}
}

The thing to note when you setup you Lambda is how to setup the “Handler” field in the “Configuration” section on AWS. It is in the format “##PACKAGE##.##CLASS##::##METHOD##”.