Simple HTTP Endpoint Example

This example demonstrates how to setup a simple HTTP GET endpoint using Java. Once you fetch it, it will reply with the current time.

Jackson is used to serialize objects to JSON.

Use Cases

  • Wrapping an existing internal or external endpoint/service

Build

It is required to build prior to deploying. You can build the deployment artifact using Gradle or Maven.

Gradle

In order to build using Gradle simply run

gradle wrapper # to build the gradle wrapper jar
./gradlew build # to build the application jar

The expected result should be similar to:

Starting a Gradle Daemon, 1 incompatible Daemon could not be reused, use --status for details
:compileJava
:processResources
:classes
:jar
:assemble
:buildZip
:compileTestJava UP-TO-DATE
:processTestResources UP-TO-DATE
:testClasses UP-TO-DATE
:test UP-TO-DATE
:check UP-TO-DATE
:build
BUILD SUCCESSFUL
Total time: 8.195 secs

Maven

In order to build using Maven simply run

mvn package

Note: you can install Maven with

  1. sdkman using sdk install maven (yes, use as default)
  2. sudo apt-get install mvn
  3. brew install maven

If you use Maven to build, then in serverless.yml you have to replace

package:
  artifact: build/distributions/aws-java-simple-http-endpoint.zip

with

package:
  artifact: target/aws-java-simple-http-endpoint.jar

before deploying.

Deploy

After having built the deployment artifact using Gradle or Maven as described above you can deploy by simply running

serverless deploy

The expected result should be similar to:

Serverless: Creating Stack...
Serverless: Checking Stack create progress...
.....
Serverless: Stack create finished...
Serverless: Uploading CloudFormation file to S3...
Serverless: Uploading service .zip file to S3...
Serverless: Updating Stack...
Serverless: Checking Stack update progress...
..............................
Serverless: Stack update finished...
Service Information
service: aws-java-simple-http-endpoint
stage: dev
region: us-east-1
api keys:
  None
endpoints:
  GET - https://XXXXXXX.execute-api.us-east-1.amazonaws.com/time
functions:
  aws-java-simple-http-endpoint-dev-currentTime: arn:aws:lambda:us-east-1:XXXXXXX:function:aws-java-simple-http-endpoint-dev-currentTime

Usage

You can now invoke the Lambda function directly and even see the resulting log via

serverless invoke --function currentTime --log

The expected result should be similar to:

{
    "statusCode": 200,
    "body": "{\"message\":\"Hello, the current time is Wed Jan 04 23:44:37 UTC 2017\"}",
    "headers": {
        "X-Powered-By": "AWS Lambda & Serverless",
        "Content-Type": "application/json"
    },
    "isBase64Encoded": false
}
--------------------------------------------------------------------
START RequestId: XXXXXXX Version: $LATEST
2004 23:44:37 <XXXXXXX> INFO  com.serverless.Handler:18 - received: {}
END RequestId: XXXXXXX
REPORT RequestId: XXXXXXX	Duration: 0.51 ms	Billed Duration: 100 ms 	Memory Size: 1024 MB	Max Memory Used: 53 MB

Finally you can send an HTTP request directly to the endpoint using a tool like curl

curl https://XXXXXXX.execute-api.us-east-1.amazonaws.com/time

The expected result should be similar to:

{"message": "Hello, the current time is Wed Jan 04 23:44:37 UTC 2017"}%

Scaling

By default, AWS Lambda limits the total concurrent executions across all functions within a given region to 1000. The default limit is a safety limit that protects you from costs due to potential runaway or recursive functions during initial development and testing. To increase this limit above the default, follow the steps in To request a limit increase for concurrent executions.