WorkerServlet.java

package {PACKAGE_NAME};

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.nio.charset.Charset;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.amazonaws.auth.AWSCredentialsProviderChain;
import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.auth.InstanceProfileCredentialsProvider;
import com.amazonaws.services.s3.AmazonS3Client;
import com.amazonaws.services.s3.model.ObjectMetadata;

/**
 * An example Amazon Elastic Beanstalk Worker Tier application. This example
 * requires a Java 7 (or higher) compiler.
 */
public class WorkerServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;
    private static final Charset UTF_8 = Charset.forName("UTF-8");

    /**
     * A client to use to access Amazon S3. Pulls credentials from the
     * {@code AwsCredentials.properties} file if found on the classpath,
     * otherwise will attempt to obtain credentials based on the IAM
     * Instance Profile associated with the EC2 instance on which it is
     * run.
     */
    private final AmazonS3Client s3 = new AmazonS3Client(
        new AWSCredentialsProviderChain(
            new InstanceProfileCredentialsProvider(),
            new ProfileCredentialsProvider("{CREDENTIAL_PROFILE}")));

    /**
     * This method is invoked to handle POST requests from the local
     * SQS daemon when a work item is pulled off of the queue. The
     * body of the request contains the message pulled off the queue.
     */
    @Override
    protected void doPost(final HttpServletRequest request,
                          final HttpServletResponse response)
            throws ServletException, IOException {

        try {

            // Parse the work to be done from the POST request body.

            WorkRequest workRequest = WorkRequest.fromJson(request.getInputStream());

            // Simulate doing some work.

            Thread.sleep(10 * 1000);

            // Write the "result" of the work into Amazon S3.

            byte[] message = workRequest.getMessage().getBytes(UTF_8);

            s3.putObject(workRequest.getBucket(),
                         workRequest.getKey(),
                         new ByteArrayInputStream(message),
                         new ObjectMetadata());

            // Signal to beanstalk that processing was successful so this work
            // item should not be retried.

            response.setStatus(200);

        } catch (RuntimeException | InterruptedException exception) {

            // Signal to beanstalk that something went wrong while processing
            // the request. The work request will be retried several times in
            // case the failure was transient (eg a temporary network issue
            // when writing to Amazon S3).

            response.setStatus(500);
            try (PrintWriter writer =
                 new PrintWriter(response.getOutputStream())) {
                exception.printStackTrace(writer);
            }
        }
    }

}