We will create a Lambda that gets triggered when messages are put into an SQS queue, and it will then send the message to another as a batch. 

The Maven pom.xml file of the project should define the following dependency:

<dependency>
    <groupId>com.amazonaws</groupId>
    <artifactId>aws-java-sdk-sqs</artifactId>
    <version>${aws.sdk.version}</version>
</dependency>

The POM file also has dependencies for aws-lambda-java-core, and inherits from the parent project, serverless-cookbook-parent-aws-java.

We can create the Java Lambda project with the following structure:

The Request.java class will correspond to our input JSON:

@Data
public class Request {
    private String queueName;
    private String message;
}

Response.java will contain a field to send the response back to the invoker:

@Data
@AllArgsConstructor
public class Response {
    private String message;
}

SqsService.java is the interface for our service class. This is not a requirement. You can directly use the implementation class or even embed all logic within the Lambda handler class itself:

public interface SqsService {
    Response createQueueAndSendMessage(Request request, LambdaLogger logger);
}

SqsServiceImpl.java is the actual service implementation. 

We can create an SQS queue and retrieve its URL, as follows:

CreateQueueResult createResult = this.sqsClient.createQueue(request.getQueueName());
logger.log("Created queue: " + createResult.getQueueUrl());

We can also get the URL, as follows:

String queueUrl = this.sqsClient.getQueueUrl(request.getQueueName()).getQueueUrl();

We can create a SendMessageRequest and send a message, as follows:

SendMessageRequest sendMessageRequest = new SendMessageRequest()
        .withQueueUrl(queueUrl)
        .withMessageBody(request.getMessage())
        .withDelaySeconds(5);
this.sqsClient.sendMessage(sendMessageRequest);

LambdaSqsSdkCreateSendHandler.java is our Lambda handler class where we initialize the SQS client and pass it to the service class. 

We can initialize the SQS client as follows:

private final AmazonSQS sqsClient;
public LambdaSqsSdkCreateSendHandler() {
    this.sqsClient = AmazonSQSClientBuilder.standard()
            .withRegion(System.getenv("AWS_REGION"))
            .build();
}

We then invoke the service method, passing the client along with the Request object:

public Response handleRequest(final Request request, final Context context) {
    final SqsService sqsService =  new SqsServiceImpl(this.sqsClient);
    return sqsService.createQueueAndSendMessage(request, context.getLogger());
}