Parse raw JSON
TL;DR: See the parser.
Sometimes you need to parse requests which have raw JSON in the body.
ambiorix::parse_multipart() only works for ‘form-data’. But Ambiorix
does not limit you to that. You can write your own request parsers or
make use of other packages. In this case, we’ll use webutils::parse_http().
Example
Say we want to select columns and filter rows
in the iris dataset when the request body is a JSON object like this:
{
"cols": ["Sepal.Length", "Petal.Width", "Species"],
"species": ["virginica", "setosa"]
}
Parser
Let’s write the parser:
box::use(
webutils[parse_http],
)
#' Parse HTTP request
#'
#' @description
#' Parses the body of an HTTP request based on the `Content-Type` of the
#' request header.
#' @details
#' Currently supports three most common types:
#' - application/x-www-form-urlencoded
#' - multipart/form-data
#' - application/json
#' @param req Request object.
#' @return Named list. Data associated with the request.
#' @export
parse_req <- \(req) {
parse_http(
body = req$rook.input$read(),
content_type = req$CONTENT_TYPE
)
}
With this, you can parse requests inside your handlers like so:
req_data <- parse_req(req)
Reprex
Here’s a full reprex:
box::use(
ambiorix[Ambiorix],
webutils[parse_http],
)
#' Handle POST at '/'
#'
#' @param req Request object.
#' @param res Response object.
#' @return `res$json()`
#' @export
home_post <- \(req, res) {
content_type <- req$CONTENT_TYPE
body <- req$rook.input$read()
if (length(body) == 0L) {
response <- list(
code = 400L,
msg = "Invalid request"
)
return(
res$set_status(400L)$json(response)
)
}
postdata <- parse_http(body, content_type)
# filter & select as necessary:
row_inds <- iris$Species %in% postdata$species
col_inds <- colnames(iris) %in% postdata$cols
data <- iris[row_inds, col_inds, drop = FALSE]
response <- list(
code = 200L,
msg = "success",
data = data
)
res$json(response)
}
app <- Ambiorix$new(port = 3000, host = "127.0.0.1")
app$
post("/", home_post)$
start()
