Get POST parameters using a HTTP server

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1

Dear all,

I want to do a small server using Julia. This service implies to receive POST parameters and returns a file. Because I want to include it inside my package, I have chosen HTTP.jl (instead of Genie) to reduce the dependencies.

Using HTTP, after many errors, I could send the file. The problem is how to receive the POST parameters from a HTML form using a handle.
I have check the documentation but I have not found any clue. I have try the request.headers and request.body but without any success.

function handle(req::HTTP.Request)
      # Get the POST parameters?
end

Any suggestion?

Thanks in advance.

Daniel

2

I can’t help you directly, since I’ve done something similar for images, but with Genie:

route("/getpic", method = POST) do
  #read payload
  raw = filespayload()
  img = ImageMagick.readblob(raw["file_name"].data)
end
Genie.startup(port,ip,async = false)

Maybe if you look inside the Genie.filespayload() function?

3

Hi Daniel,

I have studied the HTTP.jl library extensively.
You would need to do:

HTTP.Handlers.serve(server_host, server_port) do request::HTTP.Request
  request_payload=String(take!(IOBuffer(request.body))))
end

request_payload is JSON string format

As side note I recently created a lighter Julia web library (only renders JSON API and HTTP Get) doing all this for you. Might want to check Dance.jl

Cheers

2 Likes
4

Did you see this example from the HTTP.jl documentation where the payload is obtained using IOBuffer(HTTP.payload(req)). This object can then be parsed with one of the julia json readers.

5

Thank you for all your suggestions!

Finally, I have done:

function handle(req::HTTP.Request)
      data = String(req.body)
     params = Dict(split.(split(data, "&"), Ref("=")))
     # Process params
end

The String(req.body) is enough when your form is simple (in my case all where input, select, and textarea), if there is a file the option suggested by @yoh-meyers is the best one. That sentence concatenate the values as: "data = “penalty_options=0.25&penalty_boolean=0&text=…”
So, the next line divide the different form values using the & and the = symbol, and create a Dictionary with the parameters. (if there is a conflictive symbol as ‘&’ or ‘=’ as the values of the variables, they are encoded).

@uwechsler thank you, but the payload function did not work for me.

Thanks again all for your ideas!

1 Like
6

To answer myself, I have develop a (not so) simple function to read parameters. It is not working with files, but it is working with “application/x-www-form-urlencoded” and “multipart/form-data” content-types:

function get_params(req::HTTP.Request)
    data = String(req.body)
    params = Dict{String,String}()

    headers = filter(x->x[1] == "Content-Type", req.headers)
    # Check there is content-type
    if (isempty(headers))
        content_type = ""
    else
        content_type = only(headers)[2]
    end

    if (content_type == "application/x-www-form-urlencoded")
        pairs = split.(split(data, "&"), Ref("="))
        params = Dict(name => HTTP.URIs.unescapeuri(value) for (name, value) in pairs)
    elseif (startswith(content_type, "multipart/form-data"))
        body = IOBuffer(data)

        # First line is the stopping line
        stopping_line = replace(readline(body), "-" => "")

        while(!eof(body))
            line = readline(body)
            text_head = r"Content-Disposition: form-data; name=\"(.*)\""
            m = match(text_head, line)

            if !isnothing(m)
                name = m.captures[1]
                _ = readline(body)
                line = readline(body)
                value = ""

                if (!occursin(stopping_line, line))
                    value = "$(line)"
                end

                while (!eof(body) && !occursin(stopping_line, line))
                    line = readline(body)

                    if (!occursin(stopping_line, line))
                        value *= "\n$(line)"
                    end
                end

                params[name] = value
            end
        end
    end
    return params
end

I have put the code if it could help anyone.

1 Like