Enterprise Java

Amazon Simple Storage Service Mock Testing In Java

Amazon S3 (Simple Storage Service) is a cloud storage solution provided by Amazon Web Services (AWS), offering scalable storage for data storage, retrieval, and management. It provides developers with a reliable, secure, and highly available infrastructure for storing and retrieving any amount of data from anywhere on the web. Let us delve into understanding Java mock testing for Amazon Simple Storage Service (S3).

1. Introduction

Amazon S3, or Simple Storage Service, is an object storage service that offers scalable storage for a variety of data types. It allows users to store and retrieve any amount of data from anywhere on the web.

1.1 Key Features of Amazon S3

  • Scalability: S3 can handle an infinite amount of data and traffic, making it suitable for businesses of any size.
  • Durability and Reliability: S3 ensures 99.999999999% (11 9’s) durability of objects over a given year.
  • Security: S3 offers robust data security features, including encryption, access control, and multi-factor authentication.
  • Versioning: Users can preserve, retrieve, and restore every version of every object in their bucket.
  • Flexible Storage Classes: S3 offers various storage classes, including Standard, Intelligent-Tiering, Glacier, and Deep Archive, allowing cost optimization based on usage.
  • Highly Available: S3 replicates data across multiple geographically dispersed data centers, ensuring high availability and fault tolerance.
  • Easy Management: S3 provides a user-friendly management console and APIs for easy organization, retrieval, and manipulation of data.

1.2 Benefits of Amazon S3

Amazon S3 revolutionizes data storage and retrieval, providing businesses with unparalleled flexibility, security, and cost-efficiency. Its seamless integration with other AWS services makes it an ideal choice for developers, startups, and enterprises seeking reliable and scalable storage solutions.

2. S3 CRUD Java Service – Code Example

To use the AWS SDK for Java in your project for implementing the S3 CRUD service, you need to include the following Maven dependency in your project’s pom.xml file:


This dependency will ensure that your project has access to the necessary AWS SDK classes and methods for interacting with Amazon S3.

2.1 Code Example

Below is a Java code example demonstrating a simple CRUD service for Amazon S3:

package com.jcg.example;

import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.AmazonS3ClientBuilder;
import com.amazonaws.services.s3.model.*;

public class S3CRUDService {
    private final AmazonS3 s3Client;

    public S3CRUDService() {
        this.s3Client = AmazonS3ClientBuilder.standard().build();

    public void createObject(String bucketName, String key, String content) {
        s3Client.putObject(bucketName, key, content);

    public String readObject(String bucketName, String key) {
        S3Object s3Object = s3Client.getObject(bucketName, key);
        S3ObjectInputStream inputStream = s3Object.getObjectContent();
        // Read content from inputStream
        return content;

    public void updateObject(String bucketName, String key, String content) {
        createObject(bucketName, key, content); // For simplicity, updating is treated as creating a new object

    public void deleteObject(String bucketName, String key) {
        s3Client.deleteObject(bucketName, key);

2.1.1 Code Breakdown

  • Import Statements: We import necessary classes from the AWS SDK for Java, including AmazonS3 for S3 client operations and various S3 model classes for handling objects and input/output streams.
  • Class Definition:
    • The S3CRUDService class declares a private field s3Client of type AmazonS3, representing the client for interacting with Amazon S3.
    • In the constructor S3CRUDService(), an instance of AmazonS3 client is created using AmazonS3ClientBuilder.standard().build().
  • CRUD Operations:
    • createObject(String bucketName, String key, String content): Uploads an object to the specified S3 bucket with the given key and content.
    • readObject(String bucketName, String key): Retrieves the object stored in the specified S3 bucket with the given key and returns its content.
    • updateObject(String bucketName, String key, String content): Updates an object in the specified S3 bucket with the given key and content. For simplicity, treats updating as creating a new object.
    • deleteObject(String bucketName, String key): Deletes the object stored in the specified S3 bucket with the given key.

3. Use S3Mock Library for Integration Testing

Integration testing is vital for ensuring that our Java service interacts correctly with the real Amazon Simple Storage Service (S3) environment. However, conducting integration tests against a live S3 environment can be challenging due to factors like network latency and costs. To overcome these challenges, we can utilize the S3Mock library, which allows us to simulate an S3 environment locally for testing purposes. With S3Mock, we can mimic S3’s behavior in our test environment, enabling comprehensive testing without relying on the actual S3 service.

3.1 How to Use S3Mock for Integration Testing?

To use S3Mock for integration testing, we follow these steps:

  • Add S3Mock Dependency: Include the S3Mock dependency in your project’s build configuration (e.g., Maven or Gradle).
  • Write Integration Tests: Write integration tests for your Java service that interacts with Amazon S3.
  • Configure S3Mock: Use the S3Mock library to set up a mock S3 environment within your test environment. This involves configuring the mock responses, defining buckets, and specifying object properties as needed.
  • Execute Tests: Execute your integration tests against the simulated S3 environment using S3Mock. This allows you to test your Java service’s interactions with S3 without making actual network calls.
  • Assertions: Write assertions within your tests to verify that your Java service behaves as expected in response to different S3 scenarios simulated by S3Mock.

Below is a code example demonstrating how to use S3Mock for integration testing:

package com.jcg.example;

import com.adobe.testing.s3mock.junit5.S3MockExtension;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.RegisterExtension;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.model.*;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;

public class S3IntegrationTest {

    // Create S3MockExtension instance
    public static final S3MockExtension s3Mock = S3MockExtension.builder().silent().build();

    public void testS3Operations() {
        // Configure S3Client to use the S3Mock instance
        S3Client s3Client = s3Mock.createS3ClientV2();

        // Perform S3 operations using the S3Client
        String bucketName = "test-bucket";
        String objectKey = "test-object";
        String content = "Hello, S3Mock!";
        // Create bucket
        // Put object
        // Get object
        GetObjectResponse getObjectResponse = s3Client.getObject(GetObjectRequest.builder()
        // Validate response
        S3Object s3Object = getObjectResponse.s3Object();
        assertEquals(content, s3Object.getObjectContent().asString(), "Object content should match");

        // Delete object

3.1.1 Code Breakdown

The S3IntegrationTest class contains a single test method named testS3Operations(), which performs various S3 operations using the S3Mock library. Let’s break down the key components of this code:

  • S3MockExtension: This test class utilizes the S3MockExtension provided by the S3Mock library. This extension allows us to create a mock S3 environment within our test environment.
  • Test Method: The testS3Operations() method is annotated with @Test, indicating that it is a test method to be executed by the testing framework (e.g., JUnit). This method demonstrates various S3 operations such as creating a bucket, putting an object, getting an object, and deleting an object.
  • S3Client: Within the test method, an S3Client instance is created using the S3MockExtension. This client is configured to interact with the mock S3 environment created by the extension.
  • S3 Operations: Using the S3Client, the test method performs several S3 operations:
    • Create Bucket: It creates a new S3 bucket with a specified name.
    • Put Object: It uploads an object to the specified bucket with a given key and content.
    • Get Object: It retrieves the object stored in the bucket with the specified key.
    • Delete Object: It deletes the object from the bucket with the specified key.
  • Assertions: After performing the S3 operations, assertions are made to validate the results. For example, it verifies that the retrieved object’s content matches the expected content.

4. Conclusion

In conclusion, this article has covered two important aspects of developing and testing applications that interact with Amazon Simple Storage Service (S3).

Firstly, we demonstrated the implementation of a simple CRUD (Create, Read, Update, Delete) service for S3 in Java. This service allows developers to perform essential operations on objects stored in S3 buckets programmatically, providing a foundation for building more complex S3-based applications.

Secondly, we explored the use of the S3Mock library for integration testing of Java applications that interact with S3. By simulating an S3 environment locally for testing purposes, developers can thoroughly test their code’s functionality without relying on the actual S3 service. This approach not only helps in identifying and fixing issues early in the development lifecycle but also reduces dependencies on external resources, leading to more robust and reliable applications.

In summary, combining the demonstration of a CRUD Java service for S3 with the utilization of the S3Mock library for integration testing provides developers with a comprehensive toolkit for developing, testing, and maintaining S3-based applications effectively.

Yatin Batra

An experience full-stack engineer well versed with Core Java, Spring/Springboot, MVC, Security, AOP, Frontend (Angular & React), and cloud technologies (such as AWS, GCP, Jenkins, Docker, K8).
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