JarCastingAWS CloudWatch Event Dispatcher for AWS Lambda
This library allows you to easily accept and processes CloudWatch events in a Java AWS Lambda.
Usage Example
Consider the following CloudWatch event (from the AWS Docs).
{
"id":"7bf73129-1428-4cd3-a780-95db273d1602",
"detail-type":"EC2 Instance State-change Notification",
"source":"aws.ec2",
"account":"123456789012",
"time":"2015-11-11T21:29:54Z",
"region":"us-east-1",
"resources":[
"arn:aws:ec2:us-east-1:123456789012:instance/i-abcd1111"
],
"detail":{
"instance-id":"i-abcd1111",
"state":"pending"
}
}
Create a class to map this event. Use the detail-type property value in the @DetailType annotation and add fields from the detail property. Create an enum for the possible values in state, based on the AWS docs linked previously.
import com.google.gson.annotations.SerializedName;
import CloudWatchEvent;
import DetailType;
@DetailType("EC2 Instance State-change Notification")
public class Ec2InstanceStateChangeEvent extends CloudWatchEvent {
@SerializedName("instance-id")
private String instanceId;
private Ec2InstanceState state;
public String instanceId() {
return instanceId;
}
public Ec2InstanceState state() {
return state;
}
}
import com.google.gson.annotations.SerializedName;
public enum Ec2InstanceState {
@SerializedName("running")
RUNNING,
@SerializedName("pending")
PENDING,
@SerializedName("shutting-down")
SHUTTING_DOWN,
@SerializedName("stopped")
STOPPED,
@SerializedName("stopping")
STOPPING,
@SerializedName("terminated")
TERMINATED,
;
}
Create a class with a method to be invoked by AWS Lambda. Create an instance of the dispatcher from this library, register a handler for the new custom event type, and dispatch events to the handler.
import com.amazonaws.services.lambda.runtime.Context;
import CloudWatchEventDispatcher;
import java.io.InputStream;
public class Lambda {
public void handle(InputStream message, Context context) {
new CloudWatchEventDispatcher(message, context)
.withEventHandler(Ec2InstanceStateChangeEvent.class, (event, ctx) -> {
ctx.getLogger().log("Instance " + event.instanceId() +
" has changed to state " + event.state());
})
.dispatch();
}
}
You can build a JAR or Zip file of these classes and upload it to AWS Lambda. If you configure it as a destination for EC2 Instance State-change Notification CloudWatch events, it will log EC2 instance state changes to CloudWatch Logs. Try it out for yourself—and modify the handler to do something more interesting than just logging!
Dependencies
This library is published to the Central Repository. It depends on Google GSON and the AWS Lambda Core libraries. You can include the library in your project with any of a number of build systems; the two most common are provided below.
Gradle
implementation("com.perihelios.aws:cloudwatch-lambda-event-dispatcher:1.0.0")
Maven
<dependency>
<groupId>com.perihelios.aws</groupId>
<artifactId>cloudwatch-lambda-event-dispatcher</artifactId>
<version>1.0.0</version>
</dependency>
Documentation
Javadocs are available for this library.
License
Copyright © 2019 Perihelios LLC.
Licensed under the Apache 2.0 License.