How do you download files from S3 in Spring Boot?

Table of Contents

• Introduction
• Steps to Download Files from S3
  • 1. Add Dependencies
  • 2. Configure AmazonS3Client
  • 3. Create a Service to Handle File Download
    • Example Service for File Download:
  • 4. Create a Controller to Expose File Download API
    • Example Controller for File Download:
  • 5. Testing the File Download API
• Practical Example
• Conclusion

Introduction

Downloading files from Amazon S3 in a Spring Boot application is a common task when interacting with cloud storage. Amazon S3 (Simple Storage Service) allows you to store and retrieve files efficiently. In this guide, we will walk you through the process of downloading files from Amazon S3 using the AWS SDK for Java in a Spring Boot application.

Steps to Download Files from S3

1. Add Dependencies

If you have not already added the required dependencies for Amazon S3, you can do so by adding the AWS SDK for S3 in your pom.xml file.

Additionally, if you're using Spring Cloud AWS, you can add this dependency:

These dependencies will enable your Spring Boot application to communicate with AWS services, including Amazon S3.

2. Configure AmazonS3Client

Before you can download files, you need to configure the AmazonS3Client in your Spring Boot application. You can do this by creating a configuration class that defines a AmazonS3 bean.

In this example, the AmazonS3Client is configured with AWS access keys and the region of the S3 bucket. Make sure to replace "your-access-key" and "your-secret-key" with your actual AWS credentials. For better security, it is recommended to use IAM roles when deploying the application.

3. Create a Service to Handle File Download

Once the AmazonS3Client is configured, you can create a service that will handle the download functionality. This service will interact with Amazon S3 to retrieve files from a specified S3 bucket.

Example Service for File Download:

In this service, the downloadFileFromS3 method retrieves an S3Object from the specified bucket and file name. The file content is returned as an InputStream that can be processed (e.g., streamed or written to a local file).

4. Create a Controller to Expose File Download API

To expose the file download functionality, create a REST controller with an endpoint that handles the file download request.

Example Controller for File Download:

In this controller, the /api/s3/download endpoint accepts a file name as a query parameter, retrieves the file from S3 using the S3Service, and returns it as an InputStreamResource. The Content-Disposition header is set to prompt the browser to download the file.

5. Testing the File Download API

After implementing the download functionality, you can test it using tools like Postman or cURL.

1. Send a GET request to http://localhost:8080/api/s3/download?fileName=myfile.txt.
2. The file myfile.txt will be retrieved from the specified S3 bucket and returned as a downloadable file in the response.

Practical Example

Let’s assume you want to download an image file called profile.jpg from your S3 bucket. Here’s how you would perform the download:

1. Use Postman to send a GET request to http://localhost:8080/api/s3/download?fileName=profile.jpg.
2. The downloadFile method in the controller will retrieve the file from S3 and send it as a response with the correct headers, prompting the browser to download the file.

Conclusion

Downloading files from Amazon S3 in a Spring Boot application is simple with the help of the AWS SDK for Java. By configuring the AmazonS3Client and creating a service to interact with S3, you can easily retrieve files from a specified bucket and serve them in your application. This approach works well for managing cloud-based file storage and enables your Spring Boot application to seamlessly handle file downloads from Amazon S3.