ktor client post multipart/form-data

Question

How can I post file as multipart/form-data use ktor client? I want to use it for telegram bot API "send document". I need to achieve the same result as the curl command

curl -F document=@"path/to/some.file" https://api.telegram.org/bot<token>/sendDocument?chat_id=<chat_id>

Cissy

Does this answer your question? Uploading files to telegram bot api using ktor – Sternlight

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. – Tyndall

Answer 1

You can use the submitFormWithBinaryData method to send mutlipart/form-data request. Here is a solution:

val client = HttpClient(Apache) {}

val file = File("path/to/some.file")
val chatId = "123"

client.submitFormWithBinaryData(
    url = "https://api.telegram.org/bot<token>/sendDocument?chat_id=$chatId",
    formData = formData {
        append("document", file.readBytes(), Headers.build {
            append(HttpHeaders.ContentDisposition, "filename=${file.name}")
        })
    }
)

Twyla

I see many examples like these but i hope nobody uses them in production because what if the file in question is 10MB... it will be leaded into memory and crash the phone. – Parlando

Can you tell how to import this File in CommonMain. – Horeb

Please can you look at my question: https://mcmap.net/q/1166096/-problem-translating-retrofit-multipart-call-to-ktor/472270 ? – Debose

Answer 2

If the file is large, you won't want to read the whole thing into memory. Instead, you can stream the upload.

val file = File("path/to/some.file")
client.submitFormWithBinaryData(
  url = "https://api.telegram.org/bot<token>/sendDocument?chat_id=$chatId",
  formData = formData {
    append(
      "document".quote(),
      InputProvider(file.length()) { file.inputStream().asInput() },
      Headers.build {
        append(HttpHeaders.ContentDisposition, "filename=${file.name.quote()}")
      }
    )
  }
)

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