Integrating Spring Boot with Minio for Direct File Upload Using Presigned Credentials, Chunked Uploads, and Merging

Spring Boot can be integrated with Minio to handle file uploads in two ways: uploading through the backend (which allows centralized authentication, permission control, and additional processing) and uploading directly from the client using a presigned credential generated by the backend.

Environment preparation

Deploy a Minio instance (e.g., http://mylocalhost:9001 ).

Spring Boot integration

1. Add the Minio dependency:

<dependency>
    <groupId>io.minio</groupId>
    <artifactId>minio</artifactId>
    <version>7.1.0</version>
</dependency>

2. Configure Minio properties in application.yml :

# application.yml
minio:
  endpoint: http://mylocalhost:9001
  accessKey: minio
  secretKey: minio123
  bucket: demo

3. Define a properties class:

@Component
@ConfigurationProperties(prefix = "minio")
public class MinioProperties {
    private String endpoint;
    private String accessKey;
    private String secretKey;
    private String bucket;
    // getters and setters
}

4. Create a Minio configuration bean:

@Configuration
public class MinioConfig {
    @Bean
    public MinioClient minioClient(MinioProperties properties) {
        try {
            MinioClient.Builder builder = MinioClient.builder();
            builder.endpoint(properties.getEndpoint());
            if (StringUtils.hasLength(properties.getAccessKey()) && StringUtils.hasLength(properties.getSecretKey())) {
                builder.credentials(properties.getAccessKey(), properties.getSecretKey());
            }
            return builder.build();
        } catch (Exception e) {
            return null;
        }
    }
}

After starting the service, the backend can generate a presigned upload policy.

Presign endpoint

@RequestMapping(value = "/presign", method = {RequestMethod.POST})
public Map
presign(@RequestBody PresignParam presignParam) {
    if (StringUtils.isEmpty(presignParam.getBucket())) {
        presignParam.setBucket("demo");
    }
    if (StringUtils.isEmpty(presignParam.getFilename())) {
        presignParam.setFilename(UUID.randomUUID().toString());
    }
    ZonedDateTime expirationDate = ZonedDateTime.now().plusMinutes(10);
    PostPolicy policy = new PostPolicy(presignParam.getBucket(), presignParam.getFilename(), expirationDate);
    try {
        Map
map = minioClient.presignedPostPolicy(policy);
        return map;
    } catch (Exception e) {
        e.printStackTrace();
    }
    return null;
}

The returned map contains fields such as bucket , x-amz-date , x-amz-signature , key , x-amz-algorithm , x-amz-credential , and policy , which the front‑end must include in the multipart form data when uploading.

Front‑end upload example

uploadFile(file, policy) {
    var formData = new FormData();
    formData.append('file', file);
    formData.append('key', policy['key']);
    formData.append('x-amz-algorithm', policy['x-amz-algorithm']);
    formData.append('x-amz-credential', policy['x-amz-credential']);
    formData.append('x-amz-signature', policy['x-amz-signature']);
    formData.append('x-amz-date', policy['x-amz-date']);
    formData.append('policy', policy['policy']);
    return new Promise((resolve, reject) => {
        $.ajax({
            method: 'POST',
            url: 'http://mylocalhost:9001/' + policy['bucket'],
            data: formData,
            contentType: false,
            processData: false,
            xhr: function () {
                var xhr = $.ajaxSettings.xhr();
                if (xhr.upload) {
                    xhr.upload.addEventListener('progress', function (e) {
                        var percentage = parseInt(e.loaded / e.total * 100);
                        vm.uploadResult = percentage + "% :" + policy['key'];
                    }, false);
                }
                return xhr;
            },
            success: function (result) {
                vm.uploadResult = '文件上传成功：' + policy['key'];
                resolve(result);
            },
            error: function () { reject(); }
        });
    });
}

Chunked (slice) upload and merge

For large files, the front‑end can split the file into 5 MB chunks, calculate an MD5 for each chunk, request a presign policy for each slice, upload them individually, and finally call a merge endpoint on the server.

@GetMapping("/compose")
public void merge() {
    List
sources = new ArrayList<>();
    sources.add(ComposeSource.builder().bucket("slice").object("0寂寞的季节.mp4").build());
    sources.add(ComposeSource.builder().bucket("slice").object("1寂寞的季节.mp4").build());
    sources.add(ComposeSource.builder().bucket("slice").object("2寂寞的季节.mp4").build());
    ComposeObjectArgs args = ComposeObjectArgs.builder()
        .bucket("demo")
        .object("寂寞的季节.mp4")
        .sources(sources)
        .build();
    try {
        minioClient.composeObject(args);
    } catch (Exception e) { e.printStackTrace(); }
}

The front‑end code for slicing, MD5 calculation, and invoking the merge API is also provided in the original article.

Complete front‑end demo page

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Minio Test</title>
    <script src="https://cdn.bootcdn.net/ajax/libs/vue/2.7.14/vue.js"></script>
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.6.4/jquery.js"></script>
    <script src="https://cdn.bootcdn.net/ajax/libs/spark-md5/3.0.2/spark-md5.min.js"></script>
</head>
<body>
    <div id="app">
        ... (Vue component code as in the article) ...
    </div>
<script>/* Vue instance code from the article */</script>
</body>
</html>

The article concludes with a call to action and promotional links, which are not part of the technical content.