How do I save an image into a mongoDB collection using Kmongo?

Question

I searched a lot today but all answers seem to be only in nodejs. I'm currently working on ktor application and I can't seem to find any way to upload images into MongoDB with KMongo.

Answer 1

You can use GridFS to store and retrieve binary files in MongoDB. Here is an example of storing an image, that is requested with the multipart/form-data method, in a test database:

import com.mongodb.client.gridfs.GridFSBuckets
import io.ktor.application.*
import io.ktor.http.*
import io.ktor.http.content.*
import io.ktor.request.*
import io.ktor.response.*
import io.ktor.routing.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext
import org.litote.kmongo.KMongo

fun main() {
    val client = KMongo.createClient()
    val database = client.getDatabase("test")
    val bucket = GridFSBuckets.create(database, "fs_file")

    embeddedServer(Netty, port = 8080) {
        routing {
            post("/image") {
                val multipartData = call.receiveMultipart()

                multipartData.forEachPart { part ->
                    if (part is PartData.FileItem) {
                        val fileName = part.originalFileName as String
                        withContext(Dispatchers.IO) {
                            bucket.uploadFromStream(fileName, part.streamProvider())
                        }

                        call.respond(HttpStatusCode.OK)
                    }
                }
            }
        }
    }.start()
}

To make a request run the following curl command: curl -v -F image.jpg=@/path/to/image.jpg http://localhost:8080/image

To inspect stored files run db.fs_file.files.find() in the mongo shell.