Invoke AWS Lambda function from AWS java SDK

Invoking an AWS Lambda Function from Java

import com.amazonaws.regions.Regions;
import com.amazonaws.services.lambda.AWSLambda;
import com.amazonaws.services.lambda.AWSLambdaClientBuilder;
import com.amazonaws.services.lambda.model.InvokeRequest;
import com.amazonaws.services.lambda.model.InvokeResult;
// ...
// (1) Define the AWS Region in which the function is to be invoked
Regions region = Regions.fromName("us-east-1");
// (2) Instantiate AWSLambdaClientBuilder to build the Lambda client
AWSLambdaClientBuilder builder = AWSLambdaClientBuilder.standard()
                                    .withRegion(region);
// (3) Build the client, which will ultimately invoke the function
AWSLambda client = builder.build();
// (4) Create an InvokeRequest with required parameters
InvokeRequest req = new InvokeRequest()
                           .withFunctionName("myFunctionName")
                           .withPayload("{ ... }"); // optional
// (5) Invoke the function and capture response
InvokeResult result = client.invoke(req);
// (6) Handle result
...

The above will invoke Lambda synchronously; however, you can also invoke asynchronously using Java Futures or callbacks.

Invocation with Access Key and Secret Key The above sample will utilize the DefaultAWSCredentialsProviderChain to utilize environment variables, EC2 Instance Profile, etc. when invoking the function. While this is often best practice, there are also scenarios when you may need to provide access and secret keys. To do so, we only need to make a small change to the code above:

import com.amazonaws.auth.AWSStaticCredentialsProvider;
import com.amazonaws.auth.BasicAWSCredentials;
// (1a) Instantiate credentials
BasicAWSCredentials credentials = new 
  BasicAWSCredentials("myAccessKey", "mySecretKey");
// (2) Modify to leverage credentials
AWSLambdaClientBuilder builder = AWSLambdaClientBuilder.standard()
  .withCredentials(new AWSStaticCredentialsProvider(credentials));                                     
  .withRegion(region);