how to extract the (json) string out of a (Akka-http) RequestEntity

[Robin Bakkerus]

Can some one help me with (I think) a very simply question, but one I could not figure out myself yet.

It is about how extract the (json) string out of the RequestEntity, inside a HttpRequest

From the command line I give a command like this:

curl -i -H "Accept: application/json" -H "Content-Type:application/json" -X POST --data '{"value":{"id":1}' http://localhost:8000/saveTsta

And this should be handled by an Akka-http server like this:

 def requestHandler(req: HttpRequest): Future[HttpResponse] = req match {

    case HttpRequest(POST, Uri.Path("/saveTsta"), _, _, _)    => saveTsta(req)

    case _: HttpRequest                                       => unknownReq(req)

  }

def saveTsta(req: HttpRequest): Future[HttpResponse] = {

    val entity:RequestEntity = req.entity

    

    val json:String = how_do_get_the_json_data_out_of(entity) ???

}

Txs in advance

[Ian Holsman]

I'm not saying this is the best way..

val postDataF: Future[ByteString] =
entity.dataBytes.fold(ByteString("")) { (z, i) => z.concat(i)}
val postData: String = Await.result(postDataF, 50.millis).decodeString("UTF-8")

> --
>>>>>>>>>>> Read the docs: http://akka.io/docs/
>>>>>>>>>>> Check the FAQ:
>>>>>>>>>>> http://doc.akka.io/docs/akka/current/additional/faq.html
>>>>>>>>>>> Search the archives: https://groups.google.com/group/akka-user
> ---
> You received this message because you are subscribed to the Google Groups
> "Akka User List" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to akka-user+...@googlegroups.com.
> To post to this group, send email to akka...@googlegroups.com.
> Visit this group at http://groups.google.com/group/akka-user.
> For more options, visit https://groups.google.com/d/optout.



--
Ian Holsman
i...@holsman.com.au
PH: + 61-3-9028 8133 / +1-(425) 998-7083

[Robin Bakkerus]

Txs Ian, your solution works but now I am running into another problem. In the result string all quotes are lost!

In my earlier post, I only included a very small porting of the cmd-line. In practice this cmd line looks more like this:

curl -i -H "Accept: application/json" -H "Content-Type:application/json" -X POST --data '{"value":{"id":null,"ofd":null,"name":"VSKkD","count":4981,"flag":false}'

after running your code, println(postDate) gives:

'{value:{id:null,ofd:null,name:VSKkD,count:4981,flag:false}'

Any idea how to extract the origial json string ?

Op zaterdag 17 januari 2015 00:49:49 UTC+1 schreef Ian Holsman:

[Mohamed Ragab]

Again, not necessarily the best solution but ..

Note: Some of the code here is in Java, so you will need to do some digging/translation

Modifying the akka.http.marshallers.jackson.Jackson (Scala)
(possibly creating your own copy with the modifications)

Adding the following

def jsonAsString(): Unmarshaller[String] =
  UnmarshallerImpl[String] { (_ec, _flowMaterializer) ⇒
    implicit val ec = _ec
    implicit val mat = _flowMaterializer
    unmarshalling.Unmarshaller.messageUnmarshallerFromEntityUnmarshaller { // isn't implicitly inferred for unknown reasons
      unmarshalling.Unmarshaller.stringUnmarshaller
        .forContentTypes(`application/json`)
    }
  }(ClassTag(classOf[String]))

You can then use the RequestVal (java)

RequestVal<String> jsonStringExtractor = RequestVals.entityAs(MyJackson.jsonAsString());

To extract the JSON String

@Override
public Route createRoute() {
    return route(
pathPrefix("jsontest").route(
        post(handleWith(stringParser, (ctx, theRequest) -> {
            System.out.println("JSON String :: "+theRequest);
            return ctx.complete(createHttpResponse("OK"));
        })))
);

Hope this helps, feedback is more than welcome

--
Mohamed

[Mark Hatton]

Hi Robin,

Have you considered using an Akka HTTP route (akin to a spray route)?  E.g.:

val route = path("saveTsta")(
  post(
    entity(as[String]){
      json =>
        System.out.println(json)
        complete(StatusCodes.OK)
    }
  )
)

Complete gist: https://gist.github.com/markhatton/17b586982f1beab30425

Mark

[Phillip Taylor]

Not only does this answer require you to have the appropriate json libraries to map from a JObject back to a string  - It can be subtly broken in that its doing String -> Json representation -> String transformation, ergo, nulls and nones, whitespace and other changes are all subject to be misrepresented compared to what was genuinely posted to the service. Use it with caution.