Aws lambda and using Java with AWS Lambda
AWS Lambda is a compute service that lets the user to run the code without provisioning or managing servers. AWS Lambda executes the code only when it is needed and scales automatically. The user pays only for the compute time that they consume – there is no charge when the user doesn’t run the code. With AWS Lambda, one can run code virtually for any type of application or backend services. AWS Lambda runs the code on a high-availability compute infrastructure and performs all the administration of the compute resources, such as server and operating system maintenance, capacity provisioning and automatic scaling, code monitoring, and logging. The user need to do is to supply the code in one of the languages that AWS Lambda supports (such as Node.js, Java, C#, and Python).
The user can use AWS Lambda to run the code in response to events, such as changes to data in an Amazon S3 bucket or an Amazon DynamoDB table to run the code in response to HTTP requests using Amazon API Gateway or to invoke the user’s code using API calls made using AWS SDKs. With the above capabilities, the user can use Lambda to easily build data processing triggers for AWS services like Amazon S3 and Amazon DynamoDB process streaming the data which is stored in Amazon Kinesis or the user can create their own back end which operates at AWS scale, performance, and security.
AWS LAMBDA– RUNS JAVA CODE IN RESPONSE TO EVENTS
Many of the AWS users are using AWS Lambda to build clean and straightforward applications which handles image and document uploads, process log files from AWS CloudTrail, and handles the data which is streamed from Amazon Kinesis, and so forth. With the newly launched synchronous invocation capability, Lambda is becoming the most favourite choice for building mobile, web, and IoT backends.
LAMBDA FUNCTION IN JAVA
AWS Lambda has become even more useful by giving the ability to write the user’s Lambda functions in Java.
The user’s code can make use of Java 8 features along with any desired Java libraries. The user can also use the AWS SDK for Java to make calls to the AWS APIs.
AWS is providing two libraries specific to Lambda: aws-lambda-java-core with interfaces for Lambda function handlers and the context object, and aws-lambda-java-events containing type definitions for AWS event sources (Amazon Simple Storage Service (S3), Amazon Simple Notification Service (SNS), Amazon DynamoDB, Amazon Kinesis, and Amazon Cognito). User can author their Lambda functions in one of the two ways. Firstly, they can use a high-level model that uses input and output objects:
public lambdaHandler( input, Context context) throws IOException;
public lambdaHandler( input) throws IOException;
If the user does not want to use POJOs or if Lambda’s serialization model does not meet the user’s needs, they can use the Stream model. This is a bit lower-level:
public void lambdaHandler(InputStream input, OutputStream output, Context context)
throws IOException;
The class in which the Lambda function is defined should include a public zero-argument constructor, or to define the handler method as static. Alternatively, the user can also implement one of the handler interfaces(RequestHandler::handleRequest or RequestStreamHandler::handleRequest) which is available within the Lambda core Java library.
PACKAGING, DEPLOYING, AND UPLOADING
User can continue to use their existing development tools. In order to prepare their compiled code with Lambda, user must create a ZIP or JAR file that contains their compiled code (CLASS files) and any desired JAR files. The handler functions should be stored in the usual Java directory structure and the JAR files must be inside a lib subdirectory. In order to make this process easy, AWS has published build approaches using popular Java deployment tools such as Maven and Gradle.
Specify a runtime of “java8” when the user uploads their ZIP file. If they implement one of the handler interfaces, then they have to provide the class name. Otherwise, they have to provide the fully qualified method reference (e.g. com.mypackage.LambdaHandler::functionHandler).
