R plumber JSON serializer auto_unbox

Question

Following the example on the page http://plumber.trestletech.com/

I wrote myfile.R as

#* @post /test
test <- function(){
list(speech='aa',source='bb',displayText='cc')
}

And I ran the plumber code on it to convert int into an API

library(plumber)
r <- plumb("~/Work/myfile.R")
r$run(port=8000)

And Now when I perform an POST request on it using I get

curl -XPOST 'localhost:8000/test
-> {"speech":["aa"],"source":["bb"],"displayText":["cc"]}

But I want the square brackets to be removed. In simple toJSON calls it can be done using auto_unbox=TRUE but how can I do it in plumber. How can I write a custom serializer and use it in the above code?

It would be easier to help you, if you provided a [reproducible example](http://stackoverflow.com/q/5963269/4303162). Post a piece of code that produces exactly the output that you already show. For this example, you could do `toJSON(fromJSON('{"speech":["aa"],"source":["bb"],"displayText":["cc"]}'), auto_unbox = TRUE)` to get rid of the square brackets. — Stibu, Jan 31 '17 at 20:21

score 8 · Accepted Answer · answered Feb 01 '17 at 08:23

I figured the process to add custom serializers. Let's say we want to make a custom serializer for JSON and name it "custom_json" myfile.R would be

#* @serializer custom_json
#* @post /test
test <- function(){
list(speech='aa',source='bb',displayText='cc')
}

And while running plumber code it would go as

library(plumber)
library(jsonlite)

custom_json <- function(){
  function(val, req, res, errorHandler){
    tryCatch({
      json <- jsonlite::toJSON(val,auto_unbox=TRUE)

      res$setHeader("Content-Type", "application/json")
      res$body <- json

      return(res$toResponse())
    }, error=function(e){
      errorHandler(req, res, e)
    })
  }
}

addSerializer("custom_json",custom_json)
r <- plumb("~/Work/myfile.R")
r$run(port=8000)

And Now when I perform an POST request on it using I get

curl -XPOST 'localhost:8000/test
-> {"speech":"aa","source":"bb","displayText":"cc"}

Already available in `plumber::serializer_unboxed_json`. See the other answer. — asachet, May 29 '19 at 13:52

score 4 · Answer 2 · edited May 29 '19 at 13:56

4

Plumber provides a number of serializers out of the box. unboxedJSON is one of them.

Simply use the @serializer unboxedJSON annotation on you endpoint.

You can also set the default serializer to be plumber::serializer_unboxed_json.

edited May 29 '19 at 13:56

asachet

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answered Oct 23 '17 at 00:17

theEricStone

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R plumber JSON serializer auto_unbox

2 Answers2