How to get a binary stream by GridFS ObjectId with Spring Data MongoDB

Question

I can\'t figure out how to stream a binary file from GridFS with spring-data-mongodb and its GridFSTemplate when I already have the right ObjectId.

Answer 1

i discovered the solution to this problem!

Just wrap the GridFSFile in a GridFsResource! This is designed to be instantiated with a GridFSFile.

public GridFsResource getUploadedFileResource(String id) {
    var file = this.gridFsTemplate.findOne(new Query(Criteria.where("_id").is(id)));
    return new GridFsResource(file);
}

@GetMapping("/{userId}/files/{id}")
public ResponseEntity getUploadedFile(
    @PathVariable Long userId,
    @PathVariable String id
){
    var user = userService
        .getCurrentUser()
        .orElseThrow(EntityNotFoundException::new);

    var resource = userService.getUploadedFileResource(id);

    try {
        return ResponseEntity
            .ok()
            .contentType(MediaType.parseMediaType(resource.getContentType()))
            .contentLength(resource.contentLength())
            .body(resource);
    } catch (IOException e) {
        return new ResponseEntity<>(HttpStatus.INTERNAL_SERVER_ERROR);
    }


}

The great advantage of this is, that you can directly pass the GridFsResource to a ResponseEntity due to the fact, that the GridFsResource extends a InputStreamResource.

Hope this helps!

Greetings Niklas