AWS S3 + Spring Boot - File Upload, Download, List, and Delete Example

Here’s how you can implement AWS S3 file upload, download, list, and delete functionalities in a Spring Boot application step-by-step.

1. Setting Up AWS S3

1. Create an AWS Account: If you don't have one, sign up for an AWS account.

2. Create an S3 Bucket:

• Log in to the AWS Management Console.
• Navigate to the S3 service.
• Click "Create bucket."
• Provide a unique bucket name and choose an appropriate region.
• Configure access permissions as needed (e.g., public or private).

2. Spring Boot Project Setup

Add the following dependency in your pom.xml (for Maven) or build.gradle (for Gradle).

Maven:

<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>s3</artifactId>
    <version>2.20.35</version> <!-- Latest version -->
</dependency>

Gradle:

implementation 'software.amazon.awssdk:s3:2.20.35'

3. Configure AWS S3

application.properties

aws.s3.access-key=your-access-key
aws.s3.secret-key=your-secret-key
aws.s3.region=your-region
aws.s3.bucket-name=your-bucket-name

4. Create AWS S3 Configuration

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import software.amazon.awssdk.auth.credentials.AwsBasicCredentials;
import software.amazon.awssdk.auth.credentials.StaticCredentialsProvider;
import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.s3.S3Client;

@Configuration
public class S3Config {

    @Value("${aws.s3.access-key}")
    private String accessKey;

    @Value("${aws.s3.secret-key}")
    private String secretKey;

    @Value("${aws.s3.region}")
    private String region;

    @Bean
    public S3Client s3Client() {
        return S3Client.builder()
                .region(Region.of(region))
                .credentialsProvider(StaticCredentialsProvider.create(
                        AwsBasicCredentials.create(accessKey, secretKey)))
                .build();
    }
}

5. Implement the S3 Service

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;
import software.amazon.awssdk.core.sync.RequestBody;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.model.*;

import java.io.IOException;
import java.util.List;
import java.util.stream.Collectors;

@Service
public class S3Service {

    @Value("${aws.s3.bucket-name}")
    private String bucketName;

    private final S3Client s3Client;

    public S3Service(S3Client s3Client) {
        this.s3Client = s3Client;
    }

    public String uploadFile(MultipartFile file) throws IOException {
        String fileName = file.getOriginalFilename();

        s3Client.putObject(
                PutObjectRequest.builder()
                        .bucket(bucketName)
                        .key(fileName)
                        .build(),
                RequestBody.fromBytes(file.getBytes())
        );
        return fileName;
    }

    public byte[] downloadFile(String fileName) {
        return s3Client.getObject(
                GetObjectRequest.builder()
                        .bucket(bucketName)
                        .key(fileName)
                        .build(),
                software.amazon.awssdk.core.sync.ResponseTransformer.toBytes()
        ).asByteArray();
    }

    public List<String> listFiles() {
        ListObjectsV2Response response = s3Client.listObjectsV2(
                ListObjectsV2Request.builder()
                        .bucket(bucketName)
                        .build()
        );

        return response.contents().stream()
                .map(S3Object::key)
                .collect(Collectors.toList());
    }

    public void deleteFile(String fileName) {
        s3Client.deleteObject(
                DeleteObjectRequest.builder()
                        .bucket(bucketName)
                        .key(fileName)
                        .build()
        );
    }
}

6. Create a Controller

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.multipart.MultipartFile;

import java.io.IOException;
import java.util.List;

@RestController
@RequestMapping("/api/s3")
public class S3Controller {

    private final S3Service s3Service;

    public S3Controller(S3Service s3Service) {
        this.s3Service = s3Service;
    }

    @PostMapping("/upload")
    public ResponseEntity<String> uploadFile(@RequestParam("file") MultipartFile file) {
        try {
            String fileName = s3Service.uploadFile(file);
            return ResponseEntity.status(HttpStatus.CREATED).body("File uploaded successfully: " + fileName);
        } catch (IOException e) {
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("File upload failed");
        }
    }

    @GetMapping("/download/{fileName}")
    public ResponseEntity<byte[]> downloadFile(@PathVariable String fileName) {
        byte[] data = s3Service.downloadFile(fileName);
        return ResponseEntity.ok()
                .header(HttpHeaders.CONTENT_DISPOSITION, "attachment; filename=\"" + fileName + "\"")
                .body(data);
    }

    @GetMapping("/list")
    public ResponseEntity<List<String>> listFiles() {
        List<String> files = s3Service.listFiles();
        return ResponseEntity.ok(files);
    }

    @DeleteMapping("/delete/{fileName}")
    public ResponseEntity<String> deleteFile(@PathVariable String fileName) {
        s3Service.deleteFile(fileName);
        return ResponseEntity.ok("File deleted successfully: " + fileName);
    }
}

7. Test Endpoints

1. Upload File

Endpoint: POST /api/s3/upload

Body: Form-data (key: file, value: file to upload)

2. Download File

Endpoint: GET /api/s3/download/{fileName}

Response: File content as application/octet-stream.

3. List Files

Endpoint: GET /api/s3/list

Response: List of file names in the bucket.

4. Delete File

Endpoint: DELETE /api/s3/delete/{fileName}

Response: Confirmation message.

8. Key Notes

• Security: Use environment variables or AWS Secrets Manager for sensitive credentials.
• File Validation: Validate file size, type, and content before upload.
• Exception Handling: Add proper exception handling to gracefully handle AWS SDK exceptions.
• CORS: Configure CORS if accessing these endpoints from a front-end application.