Return a csv file from spring

FileResponseResource.java

public class FileResponseResource extends ByteArrayResource {

    private final String fileName;
    private final int fileLength;

    public FileResponseResource(String fileName, final byte[] byteArray) {
        super(byteArray);
        this.fileName = Objects.requireNonNull(fileName);
        this.fileLength = byteArray.length;
    }

    @Override
    public String getFilename() {
        return fileName;
    }

    @Override
    public long contentLength() {
        return fileLength;
    }
    
    public HttpHeaders createHeaders() {
        HttpHeaders httpHeaders = new HttpHeaders();
        httpHeaders.set(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_OCTET_STREAM_VALUE);
        ContentDisposition contentDisposition = ContentDisposition.attachment()
            .filename(fileName)
            .build();
        httpHeaders.set(HttpHeaders.CONTENT_DISPOSITION, contentDisposition.toString());
        return httpHeaders;
    }
}

ResourceDemoController.java

@RestController
public class ResourceDemoController {

    @GetMapping(value = "/get-demo-resource", produces = {"text/csv"})
    public ResponseEntity<Resource> getResource() {
        String output = "Header\nHello World";
        FileResponseResource resource = new FileResponseResource("output.csv", output.getBytes(StandardCharsets.UTF_8));
        
        return new ResponseEntity<>(
            resource,
            resource.createHeaders(),
            HttpStatus.OK
        );        
    }
}