How to Upload Files to Amazon S3 Buckets in Spring Boot

In Amazon S3, files or any other data are stored as objects in buckets. A bucket is nothing but a logical container for objects in S3.

Follow these steps to upload files to an Amazon S3 bucket in a Spring Boot application:

1. Create a Spring Boot Project:

We assume you have a Spring Boot project set up and ready. If not, you can create one using Spring Initializr or your preferred approach.

2. Add Amazon SDK Dependencies:

Add the AWS Java SDK For Amazon S3 dependency to your Spring Boot project:

For Maven:

<dependency>
    <groupid>com.amazonaws</groupid>
    <artifactid>aws-java-sdk-s3</artifactid>
    <version>1.12.556</version>
</dependency>

For Gradle:

implementation group: 'com.amazonaws', name: 'aws-java-sdk-s3', version: '1.12.556'

3. Add Configurations:

To access S3 bucket from a Spring Boot project, you'll need to configure your project with AWS credentials. You can do this by providing your AWS access key and secret key, which can be set in your application.properties or application.yml file or loaded from environment variables. For example, in your application.properties file:

server.port=8080

aws.access-key = your-aws-access-key
aws.access-secret-key = your-aws-secret-key
aws.region = us-east-1

4. Create an AmazonS3Client:

Create a bean for the AmazonS3 client in your Spring Boot application configuration class. You can use the @Configuration annotation to create a configuration class:

package com.example.app.config;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import com.amazonaws.auth.AWSStaticCredentialsProvider;
import com.amazonaws.auth.BasicAWSCredentials;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.AmazonS3ClientBuilder;

@Configuration
public class AmazonS3Config {

  private String awsAccessKey;
  private String awsAccessSecretKey;
  private String awsRegion;

  public AmazonS3Config(@Value(value = "${aws.access-key}") String awsAccessKey,
      @Value(value = "${aws.access-secret-key}") String awsAccessSecretKey,
      @Value(value = "${aws.region}") String awsRegion) {
    this.awsAccessKey = awsAccessKey;
    this.awsAccessSecretKey = awsAccessSecretKey;
    this.awsRegion = awsRegion;
  }

  public AWSStaticCredentialsProvider getAwsCredentialsProvider() {
    BasicAWSCredentials awsCred =
        new BasicAWSCredentials(this.awsAccessKey, this.awsAccessSecretKey);
    return new AWSStaticCredentialsProvider(awsCred);
  }

  @Bean
  public AmazonS3 getAmazonS3Client() {
    return AmazonS3ClientBuilder.standard().withRegion(this.awsRegion)
        .withCredentials(getAwsCredentialsProvider()).build();
  }

}

5. Create a Service:

Create a service interface named S3FileUploadService with a method for uploading files to your S3 bucket:

package com.example.app.service;

import java.util.Map;
import org.springframework.web.multipart.MultipartFile;

public interface S3FileUploadService {

  Map<String, String> uploadFileToS3(MultipartFile multipartfile);

}

6. Create a Service Implementation:

Create an implementation class that implements the S3FileUploadService interface and handles the business logic. Let's create a class called S3FileUploadServiceImpl:

package com.example.app.service.impl;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.multipart.MultipartFile;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.model.CannedAccessControlList;
import com.amazonaws.services.s3.model.PutObjectRequest;
import com.example.app.service.S3FileUploadService;

@Service
public class S3FileUploadServiceImpl implements S3FileUploadService {

  private String s3BaseUrl = "https://s3-us-east-1.s3.amazonaws.com/";

  private String bucketName = "my-test-bucket";

  private String folderName = "/myfolder/images/";

  @Autowired
  private AmazonS3 s3Client;

  @Override
  public Map<String, String> uploadFileToS3(MultipartFile multipartfile) {
    Map<String, String> response = new HashMap<>();

    if (multipartfile != null && !multipartfile.isEmpty()) {

      String filePathName = multipartfile.getOriginalFilename();

      File file = new File(filePathName);

      try (FileOutputStream fos = new FileOutputStream(file)) {

        if (!file.exists()) {
          file.createNewFile();
        }

        fos.write(multipartfile.getBytes());
        fos.flush();

        /* uploading file to S3 */
        s3Client.putObject(new PutObjectRequest(bucketName, folderName + "/" + file.getName(), file)
            .withCannedAcl(CannedAccessControlList.PublicRead));

        /* Url location of the uploaded file in S3. You should save it in database */
        String s3FileAccessUrl = s3BaseUrl.concat(bucketName).concat(folderName)
            .concat(file.getName()).replaceAll("\\s", "+");

        response.put("fileUrl", s3FileAccessUrl);

        file.delete();

      } catch (FileNotFoundException e) {
        e.printStackTrace();
      } catch (IOException e) {
        e.printStackTrace();
      }
    }
    return response;
  }

}

7. Create a Web Controller:

Create a controller class named S3FileUploadController. It will handle HTTP requests and interact with the S3FileUploadService to upload files to your S3 bucket:

package com.example.app.controller;

import java.util.Map;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestPart;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.MultipartFile;
import com.example.app.service.S3FileUploadService;

@RestController
@RequestMapping(path = "/files")
public class S3FileUploadController {

  @Autowired
  private S3FileUploadService s3FileUploadService;

  @PostMapping(value = "/upload")
  public ResponseEntity<Map<String, String>> uploadFile(
      @RequestPart(name = "multipartfile", required = true) MultipartFile multipartfile) {

    return ResponseEntity.ok(s3FileUploadService.uploadFileToS3(multipartfile));
  }

}