AWS S3 Client – Local Stack – Test Container

November 18, 2022 Admin Comments 0 Comment

Test Container

Test container is a third party Java library which offers to test or validate anything that can run in a Docker container. For Example, we can create lightweight database instances of MySQL, PostgreSQL or Oracle database to test our data access layer code (DAO , Repositories). Similarly we can test our AWS cloud services like server less apps without actually using the cloud. We can do this with the help of LocalStack, a fully functional local AWS cloud stack.

Local Stack

LocalStack is a cloud service emulator. We can able to run AWS applications like Lambda, S3 entirely on your laptop or machine without connecting to a remote cloud provider.

AWS S3 Client with Local Stack and Test Container

Why It is needed ?

We can able to connect to AWS services like S3 from Java using their SDK’s. But here the problem is, if we wants to validate our code then we are need to connect cloud sandboxes using AWS SAM or anything like that. And While we access the cloud services, It is billable as well. Secondly we can not write unit test or integration test for this sources in a efficient way which would be a another downside of it. So In this article, we are going to learn to write unit testing for AWS S3 services with the help of Local stack and Test containers. Let’s dive into that. Cheers.

Prerequisite

Java
Maven
Docker

Create a Spring initializer project

First, I am creating basic spring initializer project with Spring boot starter, Spring boot test and AWS SDK maven dependencies.

<dependency>
            <groupId>com.amazonaws</groupId>
            <artifactId>aws-java-sdk</artifactId>
            <version>1.11.163</version>
</dependency>

Creating AWS S3 Client

Second, now I am creating AWS S3 client with simple upload object functionality. Here I am validating whether the bucket is exist or not, followed by uploading an object into the S3 storage system.

package awsservicestutorial.client;

import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.model.ObjectMetadata;

import java.io.IOException;
import java.io.InputStream;
import java.net.URLConnection;
import java.nio.file.Files;
import java.nio.file.Path;

public class AwsS3Client {

    private final AmazonS3 amazonS3;

    public AwsS3Client(final AmazonS3 amazonS3) {
        this.amazonS3 = amazonS3;
    }

    public void uploadObject(final String bucketName, final Path path) throws IOException {

        isBucketExists(bucketName);

        final String filename = path.getFileName().toString();

        final ObjectMetadata metadata = new ObjectMetadata();
        metadata.setContentType(URLConnection.guessContentTypeFromName(filename));
        metadata.setSSEAlgorithm("AES256");
        metadata.setContentLength(Files.size(path));

        try(final InputStream stream = Files.newInputStream(path)){
            amazonS3.putObject(bucketName, filename, stream, metadata);
        }
    }

    private void isBucketExists(final String bucketName) {
        if(!amazonS3.doesBucketExist(bucketName)) {
            throw new IllegalStateException(String.format("Bucket %s does not exist", bucketName));
        }
    }

}

Local Stack and Test Container Dependencies

Add the following dependency to your pom.xml for using local stack and test container libraries.

        <dependency>
            <groupId>org.testcontainers</groupId>
            <artifactId>localstack</artifactId>
            <version>1.17.6</version>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.testcontainers</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>1.17.6</version>
            <scope>test</scope>
        </dependency>

Here I am using Junit-5 for unit testing the application. It is up to to decide whether Junit 5 or 4. We can do this with Junit 4 as well.